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Linux/kernel/workqueue.c

  1 /*
  2  * kernel/workqueue.c - generic async execution with shared worker pool
  3  *
  4  * Copyright (C) 2002           Ingo Molnar
  5  *
  6  *   Derived from the taskqueue/keventd code by:
  7  *     David Woodhouse <dwmw2@infradead.org>
  8  *     Andrew Morton
  9  *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
 10  *     Theodore Ts'o <tytso@mit.edu>
 11  *
 12  * Made to use alloc_percpu by Christoph Lameter.
 13  *
 14  * Copyright (C) 2010           SUSE Linux Products GmbH
 15  * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
 16  *
 17  * This is the generic async execution mechanism.  Work items as are
 18  * executed in process context.  The worker pool is shared and
 19  * automatically managed.  There are two worker pools for each CPU (one for
 20  * normal work items and the other for high priority ones) and some extra
 21  * pools for workqueues which are not bound to any specific CPU - the
 22  * number of these backing pools is dynamic.
 23  *
 24  * Please read Documentation/workqueue.txt for details.
 25  */
 26 
 27 #include <linux/export.h>
 28 #include <linux/kernel.h>
 29 #include <linux/sched.h>
 30 #include <linux/init.h>
 31 #include <linux/signal.h>
 32 #include <linux/completion.h>
 33 #include <linux/workqueue.h>
 34 #include <linux/slab.h>
 35 #include <linux/cpu.h>
 36 #include <linux/notifier.h>
 37 #include <linux/kthread.h>
 38 #include <linux/hardirq.h>
 39 #include <linux/mempolicy.h>
 40 #include <linux/freezer.h>
 41 #include <linux/kallsyms.h>
 42 #include <linux/debug_locks.h>
 43 #include <linux/lockdep.h>
 44 #include <linux/idr.h>
 45 #include <linux/jhash.h>
 46 #include <linux/hashtable.h>
 47 #include <linux/rculist.h>
 48 #include <linux/nodemask.h>
 49 #include <linux/moduleparam.h>
 50 #include <linux/uaccess.h>
 51 
 52 #include "workqueue_internal.h"
 53 
 54 enum {
 55         /*
 56          * worker_pool flags
 57          *
 58          * A bound pool is either associated or disassociated with its CPU.
 59          * While associated (!DISASSOCIATED), all workers are bound to the
 60          * CPU and none has %WORKER_UNBOUND set and concurrency management
 61          * is in effect.
 62          *
 63          * While DISASSOCIATED, the cpu may be offline and all workers have
 64          * %WORKER_UNBOUND set and concurrency management disabled, and may
 65          * be executing on any CPU.  The pool behaves as an unbound one.
 66          *
 67          * Note that DISASSOCIATED should be flipped only while holding
 68          * attach_mutex to avoid changing binding state while
 69          * worker_attach_to_pool() is in progress.
 70          */
 71         POOL_DISASSOCIATED      = 1 << 2,       /* cpu can't serve workers */
 72 
 73         /* worker flags */
 74         WORKER_DIE              = 1 << 1,       /* die die die */
 75         WORKER_IDLE             = 1 << 2,       /* is idle */
 76         WORKER_PREP             = 1 << 3,       /* preparing to run works */
 77         WORKER_CPU_INTENSIVE    = 1 << 6,       /* cpu intensive */
 78         WORKER_UNBOUND          = 1 << 7,       /* worker is unbound */
 79         WORKER_REBOUND          = 1 << 8,       /* worker was rebound */
 80 
 81         WORKER_NOT_RUNNING      = WORKER_PREP | WORKER_CPU_INTENSIVE |
 82                                   WORKER_UNBOUND | WORKER_REBOUND,
 83 
 84         NR_STD_WORKER_POOLS     = 2,            /* # standard pools per cpu */
 85 
 86         UNBOUND_POOL_HASH_ORDER = 6,            /* hashed by pool->attrs */
 87         BUSY_WORKER_HASH_ORDER  = 6,            /* 64 pointers */
 88 
 89         MAX_IDLE_WORKERS_RATIO  = 4,            /* 1/4 of busy can be idle */
 90         IDLE_WORKER_TIMEOUT     = 300 * HZ,     /* keep idle ones for 5 mins */
 91 
 92         MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
 93                                                 /* call for help after 10ms
 94                                                    (min two ticks) */
 95         MAYDAY_INTERVAL         = HZ / 10,      /* and then every 100ms */
 96         CREATE_COOLDOWN         = HZ,           /* time to breath after fail */
 97 
 98         /*
 99          * Rescue workers are used only on emergencies and shared by
100          * all cpus.  Give MIN_NICE.
101          */
102         RESCUER_NICE_LEVEL      = MIN_NICE,
103         HIGHPRI_NICE_LEVEL      = MIN_NICE,
104 
105         WQ_NAME_LEN             = 24,
106 };
107 
108 /*
109  * Structure fields follow one of the following exclusion rules.
110  *
111  * I: Modifiable by initialization/destruction paths and read-only for
112  *    everyone else.
113  *
114  * P: Preemption protected.  Disabling preemption is enough and should
115  *    only be modified and accessed from the local cpu.
116  *
117  * L: pool->lock protected.  Access with pool->lock held.
118  *
119  * X: During normal operation, modification requires pool->lock and should
120  *    be done only from local cpu.  Either disabling preemption on local
121  *    cpu or grabbing pool->lock is enough for read access.  If
122  *    POOL_DISASSOCIATED is set, it's identical to L.
123  *
124  * A: pool->attach_mutex protected.
125  *
126  * PL: wq_pool_mutex protected.
127  *
128  * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
129  *
130  * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
131  *
132  * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
133  *      sched-RCU for reads.
134  *
135  * WQ: wq->mutex protected.
136  *
137  * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
138  *
139  * MD: wq_mayday_lock protected.
140  */
141 
142 /* struct worker is defined in workqueue_internal.h */
143 
144 struct worker_pool {
145         spinlock_t              lock;           /* the pool lock */
146         int                     cpu;            /* I: the associated cpu */
147         int                     node;           /* I: the associated node ID */
148         int                     id;             /* I: pool ID */
149         unsigned int            flags;          /* X: flags */
150 
151         unsigned long           watchdog_ts;    /* L: watchdog timestamp */
152 
153         struct list_head        worklist;       /* L: list of pending works */
154         int                     nr_workers;     /* L: total number of workers */
155 
156         /* nr_idle includes the ones off idle_list for rebinding */
157         int                     nr_idle;        /* L: currently idle ones */
158 
159         struct list_head        idle_list;      /* X: list of idle workers */
160         struct timer_list       idle_timer;     /* L: worker idle timeout */
161         struct timer_list       mayday_timer;   /* L: SOS timer for workers */
162 
163         /* a workers is either on busy_hash or idle_list, or the manager */
164         DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
165                                                 /* L: hash of busy workers */
166 
167         /* see manage_workers() for details on the two manager mutexes */
168         struct mutex            manager_arb;    /* manager arbitration */
169         struct worker           *manager;       /* L: purely informational */
170         struct mutex            attach_mutex;   /* attach/detach exclusion */
171         struct list_head        workers;        /* A: attached workers */
172         struct completion       *detach_completion; /* all workers detached */
173 
174         struct ida              worker_ida;     /* worker IDs for task name */
175 
176         struct workqueue_attrs  *attrs;         /* I: worker attributes */
177         struct hlist_node       hash_node;      /* PL: unbound_pool_hash node */
178         int                     refcnt;         /* PL: refcnt for unbound pools */
179 
180         /*
181          * The current concurrency level.  As it's likely to be accessed
182          * from other CPUs during try_to_wake_up(), put it in a separate
183          * cacheline.
184          */
185         atomic_t                nr_running ____cacheline_aligned_in_smp;
186 
187         /*
188          * Destruction of pool is sched-RCU protected to allow dereferences
189          * from get_work_pool().
190          */
191         struct rcu_head         rcu;
192 } ____cacheline_aligned_in_smp;
193 
194 /*
195  * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
196  * of work_struct->data are used for flags and the remaining high bits
197  * point to the pwq; thus, pwqs need to be aligned at two's power of the
198  * number of flag bits.
199  */
200 struct pool_workqueue {
201         struct worker_pool      *pool;          /* I: the associated pool */
202         struct workqueue_struct *wq;            /* I: the owning workqueue */
203         int                     work_color;     /* L: current color */
204         int                     flush_color;    /* L: flushing color */
205         int                     refcnt;         /* L: reference count */
206         int                     nr_in_flight[WORK_NR_COLORS];
207                                                 /* L: nr of in_flight works */
208         int                     nr_active;      /* L: nr of active works */
209         int                     max_active;     /* L: max active works */
210         struct list_head        delayed_works;  /* L: delayed works */
211         struct list_head        pwqs_node;      /* WR: node on wq->pwqs */
212         struct list_head        mayday_node;    /* MD: node on wq->maydays */
213 
214         /*
215          * Release of unbound pwq is punted to system_wq.  See put_pwq()
216          * and pwq_unbound_release_workfn() for details.  pool_workqueue
217          * itself is also sched-RCU protected so that the first pwq can be
218          * determined without grabbing wq->mutex.
219          */
220         struct work_struct      unbound_release_work;
221         struct rcu_head         rcu;
222 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
223 
224 /*
225  * Structure used to wait for workqueue flush.
226  */
227 struct wq_flusher {
228         struct list_head        list;           /* WQ: list of flushers */
229         int                     flush_color;    /* WQ: flush color waiting for */
230         struct completion       done;           /* flush completion */
231 };
232 
233 struct wq_device;
234 
235 /*
236  * The externally visible workqueue.  It relays the issued work items to
237  * the appropriate worker_pool through its pool_workqueues.
238  */
239 struct workqueue_struct {
240         struct list_head        pwqs;           /* WR: all pwqs of this wq */
241         struct list_head        list;           /* PR: list of all workqueues */
242 
243         struct mutex            mutex;          /* protects this wq */
244         int                     work_color;     /* WQ: current work color */
245         int                     flush_color;    /* WQ: current flush color */
246         atomic_t                nr_pwqs_to_flush; /* flush in progress */
247         struct wq_flusher       *first_flusher; /* WQ: first flusher */
248         struct list_head        flusher_queue;  /* WQ: flush waiters */
249         struct list_head        flusher_overflow; /* WQ: flush overflow list */
250 
251         struct list_head        maydays;        /* MD: pwqs requesting rescue */
252         struct worker           *rescuer;       /* I: rescue worker */
253 
254         int                     nr_drainers;    /* WQ: drain in progress */
255         int                     saved_max_active; /* WQ: saved pwq max_active */
256 
257         struct workqueue_attrs  *unbound_attrs; /* PW: only for unbound wqs */
258         struct pool_workqueue   *dfl_pwq;       /* PW: only for unbound wqs */
259 
260 #ifdef CONFIG_SYSFS
261         struct wq_device        *wq_dev;        /* I: for sysfs interface */
262 #endif
263 #ifdef CONFIG_LOCKDEP
264         struct lockdep_map      lockdep_map;
265 #endif
266         char                    name[WQ_NAME_LEN]; /* I: workqueue name */
267 
268         /*
269          * Destruction of workqueue_struct is sched-RCU protected to allow
270          * walking the workqueues list without grabbing wq_pool_mutex.
271          * This is used to dump all workqueues from sysrq.
272          */
273         struct rcu_head         rcu;
274 
275         /* hot fields used during command issue, aligned to cacheline */
276         unsigned int            flags ____cacheline_aligned; /* WQ: WQ_* flags */
277         struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
278         struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
279 };
280 
281 static struct kmem_cache *pwq_cache;
282 
283 static cpumask_var_t *wq_numa_possible_cpumask;
284                                         /* possible CPUs of each node */
285 
286 static bool wq_disable_numa;
287 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
288 
289 /* see the comment above the definition of WQ_POWER_EFFICIENT */
290 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
291 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
292 
293 static bool wq_online;                  /* can kworkers be created yet? */
294 
295 static bool wq_numa_enabled;            /* unbound NUMA affinity enabled */
296 
297 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
298 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
299 
300 static DEFINE_MUTEX(wq_pool_mutex);     /* protects pools and workqueues list */
301 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
302 
303 static LIST_HEAD(workqueues);           /* PR: list of all workqueues */
304 static bool workqueue_freezing;         /* PL: have wqs started freezing? */
305 
306 /* PL: allowable cpus for unbound wqs and work items */
307 static cpumask_var_t wq_unbound_cpumask;
308 
309 /* CPU where unbound work was last round robin scheduled from this CPU */
310 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
311 
312 /*
313  * Local execution of unbound work items is no longer guaranteed.  The
314  * following always forces round-robin CPU selection on unbound work items
315  * to uncover usages which depend on it.
316  */
317 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
318 static bool wq_debug_force_rr_cpu = true;
319 #else
320 static bool wq_debug_force_rr_cpu = false;
321 #endif
322 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
323 
324 /* the per-cpu worker pools */
325 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
326 
327 static DEFINE_IDR(worker_pool_idr);     /* PR: idr of all pools */
328 
329 /* PL: hash of all unbound pools keyed by pool->attrs */
330 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
331 
332 /* I: attributes used when instantiating standard unbound pools on demand */
333 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
334 
335 /* I: attributes used when instantiating ordered pools on demand */
336 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
337 
338 struct workqueue_struct *system_wq __read_mostly;
339 EXPORT_SYMBOL(system_wq);
340 struct workqueue_struct *system_highpri_wq __read_mostly;
341 EXPORT_SYMBOL_GPL(system_highpri_wq);
342 struct workqueue_struct *system_long_wq __read_mostly;
343 EXPORT_SYMBOL_GPL(system_long_wq);
344 struct workqueue_struct *system_unbound_wq __read_mostly;
345 EXPORT_SYMBOL_GPL(system_unbound_wq);
346 struct workqueue_struct *system_freezable_wq __read_mostly;
347 EXPORT_SYMBOL_GPL(system_freezable_wq);
348 struct workqueue_struct *system_power_efficient_wq __read_mostly;
349 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
350 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
351 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
352 
353 static int worker_thread(void *__worker);
354 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
355 
356 #define CREATE_TRACE_POINTS
357 #include <trace/events/workqueue.h>
358 
359 #define assert_rcu_or_pool_mutex()                                      \
360         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
361                          !lockdep_is_held(&wq_pool_mutex),              \
362                          "sched RCU or wq_pool_mutex should be held")
363 
364 #define assert_rcu_or_wq_mutex(wq)                                      \
365         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
366                          !lockdep_is_held(&wq->mutex),                  \
367                          "sched RCU or wq->mutex should be held")
368 
369 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)                        \
370         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
371                          !lockdep_is_held(&wq->mutex) &&                \
372                          !lockdep_is_held(&wq_pool_mutex),              \
373                          "sched RCU, wq->mutex or wq_pool_mutex should be held")
374 
375 #define for_each_cpu_worker_pool(pool, cpu)                             \
376         for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];               \
377              (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
378              (pool)++)
379 
380 /**
381  * for_each_pool - iterate through all worker_pools in the system
382  * @pool: iteration cursor
383  * @pi: integer used for iteration
384  *
385  * This must be called either with wq_pool_mutex held or sched RCU read
386  * locked.  If the pool needs to be used beyond the locking in effect, the
387  * caller is responsible for guaranteeing that the pool stays online.
388  *
389  * The if/else clause exists only for the lockdep assertion and can be
390  * ignored.
391  */
392 #define for_each_pool(pool, pi)                                         \
393         idr_for_each_entry(&worker_pool_idr, pool, pi)                  \
394                 if (({ assert_rcu_or_pool_mutex(); false; })) { }       \
395                 else
396 
397 /**
398  * for_each_pool_worker - iterate through all workers of a worker_pool
399  * @worker: iteration cursor
400  * @pool: worker_pool to iterate workers of
401  *
402  * This must be called with @pool->attach_mutex.
403  *
404  * The if/else clause exists only for the lockdep assertion and can be
405  * ignored.
406  */
407 #define for_each_pool_worker(worker, pool)                              \
408         list_for_each_entry((worker), &(pool)->workers, node)           \
409                 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
410                 else
411 
412 /**
413  * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
414  * @pwq: iteration cursor
415  * @wq: the target workqueue
416  *
417  * This must be called either with wq->mutex held or sched RCU read locked.
418  * If the pwq needs to be used beyond the locking in effect, the caller is
419  * responsible for guaranteeing that the pwq stays online.
420  *
421  * The if/else clause exists only for the lockdep assertion and can be
422  * ignored.
423  */
424 #define for_each_pwq(pwq, wq)                                           \
425         list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)          \
426                 if (({ assert_rcu_or_wq_mutex(wq); false; })) { }       \
427                 else
428 
429 #ifdef CONFIG_DEBUG_OBJECTS_WORK
430 
431 static struct debug_obj_descr work_debug_descr;
432 
433 static void *work_debug_hint(void *addr)
434 {
435         return ((struct work_struct *) addr)->func;
436 }
437 
438 static bool work_is_static_object(void *addr)
439 {
440         struct work_struct *work = addr;
441 
442         return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
443 }
444 
445 /*
446  * fixup_init is called when:
447  * - an active object is initialized
448  */
449 static bool work_fixup_init(void *addr, enum debug_obj_state state)
450 {
451         struct work_struct *work = addr;
452 
453         switch (state) {
454         case ODEBUG_STATE_ACTIVE:
455                 cancel_work_sync(work);
456                 debug_object_init(work, &work_debug_descr);
457                 return true;
458         default:
459                 return false;
460         }
461 }
462 
463 /*
464  * fixup_free is called when:
465  * - an active object is freed
466  */
467 static bool work_fixup_free(void *addr, enum debug_obj_state state)
468 {
469         struct work_struct *work = addr;
470 
471         switch (state) {
472         case ODEBUG_STATE_ACTIVE:
473                 cancel_work_sync(work);
474                 debug_object_free(work, &work_debug_descr);
475                 return true;
476         default:
477                 return false;
478         }
479 }
480 
481 static struct debug_obj_descr work_debug_descr = {
482         .name           = "work_struct",
483         .debug_hint     = work_debug_hint,
484         .is_static_object = work_is_static_object,
485         .fixup_init     = work_fixup_init,
486         .fixup_free     = work_fixup_free,
487 };
488 
489 static inline void debug_work_activate(struct work_struct *work)
490 {
491         debug_object_activate(work, &work_debug_descr);
492 }
493 
494 static inline void debug_work_deactivate(struct work_struct *work)
495 {
496         debug_object_deactivate(work, &work_debug_descr);
497 }
498 
499 void __init_work(struct work_struct *work, int onstack)
500 {
501         if (onstack)
502                 debug_object_init_on_stack(work, &work_debug_descr);
503         else
504                 debug_object_init(work, &work_debug_descr);
505 }
506 EXPORT_SYMBOL_GPL(__init_work);
507 
508 void destroy_work_on_stack(struct work_struct *work)
509 {
510         debug_object_free(work, &work_debug_descr);
511 }
512 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
513 
514 void destroy_delayed_work_on_stack(struct delayed_work *work)
515 {
516         destroy_timer_on_stack(&work->timer);
517         debug_object_free(&work->work, &work_debug_descr);
518 }
519 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
520 
521 #else
522 static inline void debug_work_activate(struct work_struct *work) { }
523 static inline void debug_work_deactivate(struct work_struct *work) { }
524 #endif
525 
526 /**
527  * worker_pool_assign_id - allocate ID and assing it to @pool
528  * @pool: the pool pointer of interest
529  *
530  * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
531  * successfully, -errno on failure.
532  */
533 static int worker_pool_assign_id(struct worker_pool *pool)
534 {
535         int ret;
536 
537         lockdep_assert_held(&wq_pool_mutex);
538 
539         ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
540                         GFP_KERNEL);
541         if (ret >= 0) {
542                 pool->id = ret;
543                 return 0;
544         }
545         return ret;
546 }
547 
548 /**
549  * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
550  * @wq: the target workqueue
551  * @node: the node ID
552  *
553  * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
554  * read locked.
555  * If the pwq needs to be used beyond the locking in effect, the caller is
556  * responsible for guaranteeing that the pwq stays online.
557  *
558  * Return: The unbound pool_workqueue for @node.
559  */
560 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
561                                                   int node)
562 {
563         assert_rcu_or_wq_mutex_or_pool_mutex(wq);
564 
565         /*
566          * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
567          * delayed item is pending.  The plan is to keep CPU -> NODE
568          * mapping valid and stable across CPU on/offlines.  Once that
569          * happens, this workaround can be removed.
570          */
571         if (unlikely(node == NUMA_NO_NODE))
572                 return wq->dfl_pwq;
573 
574         return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
575 }
576 
577 static unsigned int work_color_to_flags(int color)
578 {
579         return color << WORK_STRUCT_COLOR_SHIFT;
580 }
581 
582 static int get_work_color(struct work_struct *work)
583 {
584         return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
585                 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
586 }
587 
588 static int work_next_color(int color)
589 {
590         return (color + 1) % WORK_NR_COLORS;
591 }
592 
593 /*
594  * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
595  * contain the pointer to the queued pwq.  Once execution starts, the flag
596  * is cleared and the high bits contain OFFQ flags and pool ID.
597  *
598  * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
599  * and clear_work_data() can be used to set the pwq, pool or clear
600  * work->data.  These functions should only be called while the work is
601  * owned - ie. while the PENDING bit is set.
602  *
603  * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
604  * corresponding to a work.  Pool is available once the work has been
605  * queued anywhere after initialization until it is sync canceled.  pwq is
606  * available only while the work item is queued.
607  *
608  * %WORK_OFFQ_CANCELING is used to mark a work item which is being
609  * canceled.  While being canceled, a work item may have its PENDING set
610  * but stay off timer and worklist for arbitrarily long and nobody should
611  * try to steal the PENDING bit.
612  */
613 static inline void set_work_data(struct work_struct *work, unsigned long data,
614                                  unsigned long flags)
615 {
616         WARN_ON_ONCE(!work_pending(work));
617         atomic_long_set(&work->data, data | flags | work_static(work));
618 }
619 
620 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
621                          unsigned long extra_flags)
622 {
623         set_work_data(work, (unsigned long)pwq,
624                       WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
625 }
626 
627 static void set_work_pool_and_keep_pending(struct work_struct *work,
628                                            int pool_id)
629 {
630         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
631                       WORK_STRUCT_PENDING);
632 }
633 
634 static void set_work_pool_and_clear_pending(struct work_struct *work,
635                                             int pool_id)
636 {
637         /*
638          * The following wmb is paired with the implied mb in
639          * test_and_set_bit(PENDING) and ensures all updates to @work made
640          * here are visible to and precede any updates by the next PENDING
641          * owner.
642          */
643         smp_wmb();
644         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
645         /*
646          * The following mb guarantees that previous clear of a PENDING bit
647          * will not be reordered with any speculative LOADS or STORES from
648          * work->current_func, which is executed afterwards.  This possible
649          * reordering can lead to a missed execution on attempt to qeueue
650          * the same @work.  E.g. consider this case:
651          *
652          *   CPU#0                         CPU#1
653          *   ----------------------------  --------------------------------
654          *
655          * 1  STORE event_indicated
656          * 2  queue_work_on() {
657          * 3    test_and_set_bit(PENDING)
658          * 4 }                             set_..._and_clear_pending() {
659          * 5                                 set_work_data() # clear bit
660          * 6                                 smp_mb()
661          * 7                               work->current_func() {
662          * 8                                  LOAD event_indicated
663          *                                 }
664          *
665          * Without an explicit full barrier speculative LOAD on line 8 can
666          * be executed before CPU#0 does STORE on line 1.  If that happens,
667          * CPU#0 observes the PENDING bit is still set and new execution of
668          * a @work is not queued in a hope, that CPU#1 will eventually
669          * finish the queued @work.  Meanwhile CPU#1 does not see
670          * event_indicated is set, because speculative LOAD was executed
671          * before actual STORE.
672          */
673         smp_mb();
674 }
675 
676 static void clear_work_data(struct work_struct *work)
677 {
678         smp_wmb();      /* see set_work_pool_and_clear_pending() */
679         set_work_data(work, WORK_STRUCT_NO_POOL, 0);
680 }
681 
682 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
683 {
684         unsigned long data = atomic_long_read(&work->data);
685 
686         if (data & WORK_STRUCT_PWQ)
687                 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
688         else
689                 return NULL;
690 }
691 
692 /**
693  * get_work_pool - return the worker_pool a given work was associated with
694  * @work: the work item of interest
695  *
696  * Pools are created and destroyed under wq_pool_mutex, and allows read
697  * access under sched-RCU read lock.  As such, this function should be
698  * called under wq_pool_mutex or with preemption disabled.
699  *
700  * All fields of the returned pool are accessible as long as the above
701  * mentioned locking is in effect.  If the returned pool needs to be used
702  * beyond the critical section, the caller is responsible for ensuring the
703  * returned pool is and stays online.
704  *
705  * Return: The worker_pool @work was last associated with.  %NULL if none.
706  */
707 static struct worker_pool *get_work_pool(struct work_struct *work)
708 {
709         unsigned long data = atomic_long_read(&work->data);
710         int pool_id;
711 
712         assert_rcu_or_pool_mutex();
713 
714         if (data & WORK_STRUCT_PWQ)
715                 return ((struct pool_workqueue *)
716                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
717 
718         pool_id = data >> WORK_OFFQ_POOL_SHIFT;
719         if (pool_id == WORK_OFFQ_POOL_NONE)
720                 return NULL;
721 
722         return idr_find(&worker_pool_idr, pool_id);
723 }
724 
725 /**
726  * get_work_pool_id - return the worker pool ID a given work is associated with
727  * @work: the work item of interest
728  *
729  * Return: The worker_pool ID @work was last associated with.
730  * %WORK_OFFQ_POOL_NONE if none.
731  */
732 static int get_work_pool_id(struct work_struct *work)
733 {
734         unsigned long data = atomic_long_read(&work->data);
735 
736         if (data & WORK_STRUCT_PWQ)
737                 return ((struct pool_workqueue *)
738                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
739 
740         return data >> WORK_OFFQ_POOL_SHIFT;
741 }
742 
743 static void mark_work_canceling(struct work_struct *work)
744 {
745         unsigned long pool_id = get_work_pool_id(work);
746 
747         pool_id <<= WORK_OFFQ_POOL_SHIFT;
748         set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
749 }
750 
751 static bool work_is_canceling(struct work_struct *work)
752 {
753         unsigned long data = atomic_long_read(&work->data);
754 
755         return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
756 }
757 
758 /*
759  * Policy functions.  These define the policies on how the global worker
760  * pools are managed.  Unless noted otherwise, these functions assume that
761  * they're being called with pool->lock held.
762  */
763 
764 static bool __need_more_worker(struct worker_pool *pool)
765 {
766         return !atomic_read(&pool->nr_running);
767 }
768 
769 /*
770  * Need to wake up a worker?  Called from anything but currently
771  * running workers.
772  *
773  * Note that, because unbound workers never contribute to nr_running, this
774  * function will always return %true for unbound pools as long as the
775  * worklist isn't empty.
776  */
777 static bool need_more_worker(struct worker_pool *pool)
778 {
779         return !list_empty(&pool->worklist) && __need_more_worker(pool);
780 }
781 
782 /* Can I start working?  Called from busy but !running workers. */
783 static bool may_start_working(struct worker_pool *pool)
784 {
785         return pool->nr_idle;
786 }
787 
788 /* Do I need to keep working?  Called from currently running workers. */
789 static bool keep_working(struct worker_pool *pool)
790 {
791         return !list_empty(&pool->worklist) &&
792                 atomic_read(&pool->nr_running) <= 1;
793 }
794 
795 /* Do we need a new worker?  Called from manager. */
796 static bool need_to_create_worker(struct worker_pool *pool)
797 {
798         return need_more_worker(pool) && !may_start_working(pool);
799 }
800 
801 /* Do we have too many workers and should some go away? */
802 static bool too_many_workers(struct worker_pool *pool)
803 {
804         bool managing = mutex_is_locked(&pool->manager_arb);
805         int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
806         int nr_busy = pool->nr_workers - nr_idle;
807 
808         return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
809 }
810 
811 /*
812  * Wake up functions.
813  */
814 
815 /* Return the first idle worker.  Safe with preemption disabled */
816 static struct worker *first_idle_worker(struct worker_pool *pool)
817 {
818         if (unlikely(list_empty(&pool->idle_list)))
819                 return NULL;
820 
821         return list_first_entry(&pool->idle_list, struct worker, entry);
822 }
823 
824 /**
825  * wake_up_worker - wake up an idle worker
826  * @pool: worker pool to wake worker from
827  *
828  * Wake up the first idle worker of @pool.
829  *
830  * CONTEXT:
831  * spin_lock_irq(pool->lock).
832  */
833 static void wake_up_worker(struct worker_pool *pool)
834 {
835         struct worker *worker = first_idle_worker(pool);
836 
837         if (likely(worker))
838                 wake_up_process(worker->task);
839 }
840 
841 /**
842  * wq_worker_waking_up - a worker is waking up
843  * @task: task waking up
844  * @cpu: CPU @task is waking up to
845  *
846  * This function is called during try_to_wake_up() when a worker is
847  * being awoken.
848  *
849  * CONTEXT:
850  * spin_lock_irq(rq->lock)
851  */
852 void wq_worker_waking_up(struct task_struct *task, int cpu)
853 {
854         struct worker *worker = kthread_data(task);
855 
856         if (!(worker->flags & WORKER_NOT_RUNNING)) {
857                 WARN_ON_ONCE(worker->pool->cpu != cpu);
858                 atomic_inc(&worker->pool->nr_running);
859         }
860 }
861 
862 /**
863  * wq_worker_sleeping - a worker is going to sleep
864  * @task: task going to sleep
865  *
866  * This function is called during schedule() when a busy worker is
867  * going to sleep.  Worker on the same cpu can be woken up by
868  * returning pointer to its task.
869  *
870  * CONTEXT:
871  * spin_lock_irq(rq->lock)
872  *
873  * Return:
874  * Worker task on @cpu to wake up, %NULL if none.
875  */
876 struct task_struct *wq_worker_sleeping(struct task_struct *task)
877 {
878         struct worker *worker = kthread_data(task), *to_wakeup = NULL;
879         struct worker_pool *pool;
880 
881         /*
882          * Rescuers, which may not have all the fields set up like normal
883          * workers, also reach here, let's not access anything before
884          * checking NOT_RUNNING.
885          */
886         if (worker->flags & WORKER_NOT_RUNNING)
887                 return NULL;
888 
889         pool = worker->pool;
890 
891         /* this can only happen on the local cpu */
892         if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
893                 return NULL;
894 
895         /*
896          * The counterpart of the following dec_and_test, implied mb,
897          * worklist not empty test sequence is in insert_work().
898          * Please read comment there.
899          *
900          * NOT_RUNNING is clear.  This means that we're bound to and
901          * running on the local cpu w/ rq lock held and preemption
902          * disabled, which in turn means that none else could be
903          * manipulating idle_list, so dereferencing idle_list without pool
904          * lock is safe.
905          */
906         if (atomic_dec_and_test(&pool->nr_running) &&
907             !list_empty(&pool->worklist))
908                 to_wakeup = first_idle_worker(pool);
909         return to_wakeup ? to_wakeup->task : NULL;
910 }
911 
912 /**
913  * worker_set_flags - set worker flags and adjust nr_running accordingly
914  * @worker: self
915  * @flags: flags to set
916  *
917  * Set @flags in @worker->flags and adjust nr_running accordingly.
918  *
919  * CONTEXT:
920  * spin_lock_irq(pool->lock)
921  */
922 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
923 {
924         struct worker_pool *pool = worker->pool;
925 
926         WARN_ON_ONCE(worker->task != current);
927 
928         /* If transitioning into NOT_RUNNING, adjust nr_running. */
929         if ((flags & WORKER_NOT_RUNNING) &&
930             !(worker->flags & WORKER_NOT_RUNNING)) {
931                 atomic_dec(&pool->nr_running);
932         }
933 
934         worker->flags |= flags;
935 }
936 
937 /**
938  * worker_clr_flags - clear worker flags and adjust nr_running accordingly
939  * @worker: self
940  * @flags: flags to clear
941  *
942  * Clear @flags in @worker->flags and adjust nr_running accordingly.
943  *
944  * CONTEXT:
945  * spin_lock_irq(pool->lock)
946  */
947 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
948 {
949         struct worker_pool *pool = worker->pool;
950         unsigned int oflags = worker->flags;
951 
952         WARN_ON_ONCE(worker->task != current);
953 
954         worker->flags &= ~flags;
955 
956         /*
957          * If transitioning out of NOT_RUNNING, increment nr_running.  Note
958          * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
959          * of multiple flags, not a single flag.
960          */
961         if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
962                 if (!(worker->flags & WORKER_NOT_RUNNING))
963                         atomic_inc(&pool->nr_running);
964 }
965 
966 /**
967  * find_worker_executing_work - find worker which is executing a work
968  * @pool: pool of interest
969  * @work: work to find worker for
970  *
971  * Find a worker which is executing @work on @pool by searching
972  * @pool->busy_hash which is keyed by the address of @work.  For a worker
973  * to match, its current execution should match the address of @work and
974  * its work function.  This is to avoid unwanted dependency between
975  * unrelated work executions through a work item being recycled while still
976  * being executed.
977  *
978  * This is a bit tricky.  A work item may be freed once its execution
979  * starts and nothing prevents the freed area from being recycled for
980  * another work item.  If the same work item address ends up being reused
981  * before the original execution finishes, workqueue will identify the
982  * recycled work item as currently executing and make it wait until the
983  * current execution finishes, introducing an unwanted dependency.
984  *
985  * This function checks the work item address and work function to avoid
986  * false positives.  Note that this isn't complete as one may construct a
987  * work function which can introduce dependency onto itself through a
988  * recycled work item.  Well, if somebody wants to shoot oneself in the
989  * foot that badly, there's only so much we can do, and if such deadlock
990  * actually occurs, it should be easy to locate the culprit work function.
991  *
992  * CONTEXT:
993  * spin_lock_irq(pool->lock).
994  *
995  * Return:
996  * Pointer to worker which is executing @work if found, %NULL
997  * otherwise.
998  */
999 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1000                                                  struct work_struct *work)
1001 {
1002         struct worker *worker;
1003 
1004         hash_for_each_possible(pool->busy_hash, worker, hentry,
1005                                (unsigned long)work)
1006                 if (worker->current_work == work &&
1007                     worker->current_func == work->func)
1008                         return worker;
1009 
1010         return NULL;
1011 }
1012 
1013 /**
1014  * move_linked_works - move linked works to a list
1015  * @work: start of series of works to be scheduled
1016  * @head: target list to append @work to
1017  * @nextp: out parameter for nested worklist walking
1018  *
1019  * Schedule linked works starting from @work to @head.  Work series to
1020  * be scheduled starts at @work and includes any consecutive work with
1021  * WORK_STRUCT_LINKED set in its predecessor.
1022  *
1023  * If @nextp is not NULL, it's updated to point to the next work of
1024  * the last scheduled work.  This allows move_linked_works() to be
1025  * nested inside outer list_for_each_entry_safe().
1026  *
1027  * CONTEXT:
1028  * spin_lock_irq(pool->lock).
1029  */
1030 static void move_linked_works(struct work_struct *work, struct list_head *head,
1031                               struct work_struct **nextp)
1032 {
1033         struct work_struct *n;
1034 
1035         /*
1036          * Linked worklist will always end before the end of the list,
1037          * use NULL for list head.
1038          */
1039         list_for_each_entry_safe_from(work, n, NULL, entry) {
1040                 list_move_tail(&work->entry, head);
1041                 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1042                         break;
1043         }
1044 
1045         /*
1046          * If we're already inside safe list traversal and have moved
1047          * multiple works to the scheduled queue, the next position
1048          * needs to be updated.
1049          */
1050         if (nextp)
1051                 *nextp = n;
1052 }
1053 
1054 /**
1055  * get_pwq - get an extra reference on the specified pool_workqueue
1056  * @pwq: pool_workqueue to get
1057  *
1058  * Obtain an extra reference on @pwq.  The caller should guarantee that
1059  * @pwq has positive refcnt and be holding the matching pool->lock.
1060  */
1061 static void get_pwq(struct pool_workqueue *pwq)
1062 {
1063         lockdep_assert_held(&pwq->pool->lock);
1064         WARN_ON_ONCE(pwq->refcnt <= 0);
1065         pwq->refcnt++;
1066 }
1067 
1068 /**
1069  * put_pwq - put a pool_workqueue reference
1070  * @pwq: pool_workqueue to put
1071  *
1072  * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
1073  * destruction.  The caller should be holding the matching pool->lock.
1074  */
1075 static void put_pwq(struct pool_workqueue *pwq)
1076 {
1077         lockdep_assert_held(&pwq->pool->lock);
1078         if (likely(--pwq->refcnt))
1079                 return;
1080         if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1081                 return;
1082         /*
1083          * @pwq can't be released under pool->lock, bounce to
1084          * pwq_unbound_release_workfn().  This never recurses on the same
1085          * pool->lock as this path is taken only for unbound workqueues and
1086          * the release work item is scheduled on a per-cpu workqueue.  To
1087          * avoid lockdep warning, unbound pool->locks are given lockdep
1088          * subclass of 1 in get_unbound_pool().
1089          */
1090         schedule_work(&pwq->unbound_release_work);
1091 }
1092 
1093 /**
1094  * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1095  * @pwq: pool_workqueue to put (can be %NULL)
1096  *
1097  * put_pwq() with locking.  This function also allows %NULL @pwq.
1098  */
1099 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1100 {
1101         if (pwq) {
1102                 /*
1103                  * As both pwqs and pools are sched-RCU protected, the
1104                  * following lock operations are safe.
1105                  */
1106                 spin_lock_irq(&pwq->pool->lock);
1107                 put_pwq(pwq);
1108                 spin_unlock_irq(&pwq->pool->lock);
1109         }
1110 }
1111 
1112 static void pwq_activate_delayed_work(struct work_struct *work)
1113 {
1114         struct pool_workqueue *pwq = get_work_pwq(work);
1115 
1116         trace_workqueue_activate_work(work);
1117         if (list_empty(&pwq->pool->worklist))
1118                 pwq->pool->watchdog_ts = jiffies;
1119         move_linked_works(work, &pwq->pool->worklist, NULL);
1120         __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1121         pwq->nr_active++;
1122 }
1123 
1124 static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1125 {
1126         struct work_struct *work = list_first_entry(&pwq->delayed_works,
1127                                                     struct work_struct, entry);
1128 
1129         pwq_activate_delayed_work(work);
1130 }
1131 
1132 /**
1133  * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1134  * @pwq: pwq of interest
1135  * @color: color of work which left the queue
1136  *
1137  * A work either has completed or is removed from pending queue,
1138  * decrement nr_in_flight of its pwq and handle workqueue flushing.
1139  *
1140  * CONTEXT:
1141  * spin_lock_irq(pool->lock).
1142  */
1143 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1144 {
1145         /* uncolored work items don't participate in flushing or nr_active */
1146         if (color == WORK_NO_COLOR)
1147                 goto out_put;
1148 
1149         pwq->nr_in_flight[color]--;
1150 
1151         pwq->nr_active--;
1152         if (!list_empty(&pwq->delayed_works)) {
1153                 /* one down, submit a delayed one */
1154                 if (pwq->nr_active < pwq->max_active)
1155                         pwq_activate_first_delayed(pwq);
1156         }
1157 
1158         /* is flush in progress and are we at the flushing tip? */
1159         if (likely(pwq->flush_color != color))
1160                 goto out_put;
1161 
1162         /* are there still in-flight works? */
1163         if (pwq->nr_in_flight[color])
1164                 goto out_put;
1165 
1166         /* this pwq is done, clear flush_color */
1167         pwq->flush_color = -1;
1168 
1169         /*
1170          * If this was the last pwq, wake up the first flusher.  It
1171          * will handle the rest.
1172          */
1173         if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1174                 complete(&pwq->wq->first_flusher->done);
1175 out_put:
1176         put_pwq(pwq);
1177 }
1178 
1179 /**
1180  * try_to_grab_pending - steal work item from worklist and disable irq
1181  * @work: work item to steal
1182  * @is_dwork: @work is a delayed_work
1183  * @flags: place to store irq state
1184  *
1185  * Try to grab PENDING bit of @work.  This function can handle @work in any
1186  * stable state - idle, on timer or on worklist.
1187  *
1188  * Return:
1189  *  1           if @work was pending and we successfully stole PENDING
1190  *  0           if @work was idle and we claimed PENDING
1191  *  -EAGAIN     if PENDING couldn't be grabbed at the moment, safe to busy-retry
1192  *  -ENOENT     if someone else is canceling @work, this state may persist
1193  *              for arbitrarily long
1194  *
1195  * Note:
1196  * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
1197  * interrupted while holding PENDING and @work off queue, irq must be
1198  * disabled on entry.  This, combined with delayed_work->timer being
1199  * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1200  *
1201  * On successful return, >= 0, irq is disabled and the caller is
1202  * responsible for releasing it using local_irq_restore(*@flags).
1203  *
1204  * This function is safe to call from any context including IRQ handler.
1205  */
1206 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1207                                unsigned long *flags)
1208 {
1209         struct worker_pool *pool;
1210         struct pool_workqueue *pwq;
1211 
1212         local_irq_save(*flags);
1213 
1214         /* try to steal the timer if it exists */
1215         if (is_dwork) {
1216                 struct delayed_work *dwork = to_delayed_work(work);
1217 
1218                 /*
1219                  * dwork->timer is irqsafe.  If del_timer() fails, it's
1220                  * guaranteed that the timer is not queued anywhere and not
1221                  * running on the local CPU.
1222                  */
1223                 if (likely(del_timer(&dwork->timer)))
1224                         return 1;
1225         }
1226 
1227         /* try to claim PENDING the normal way */
1228         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1229                 return 0;
1230 
1231         /*
1232          * The queueing is in progress, or it is already queued. Try to
1233          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1234          */
1235         pool = get_work_pool(work);
1236         if (!pool)
1237                 goto fail;
1238 
1239         spin_lock(&pool->lock);
1240         /*
1241          * work->data is guaranteed to point to pwq only while the work
1242          * item is queued on pwq->wq, and both updating work->data to point
1243          * to pwq on queueing and to pool on dequeueing are done under
1244          * pwq->pool->lock.  This in turn guarantees that, if work->data
1245          * points to pwq which is associated with a locked pool, the work
1246          * item is currently queued on that pool.
1247          */
1248         pwq = get_work_pwq(work);
1249         if (pwq && pwq->pool == pool) {
1250                 debug_work_deactivate(work);
1251 
1252                 /*
1253                  * A delayed work item cannot be grabbed directly because
1254                  * it might have linked NO_COLOR work items which, if left
1255                  * on the delayed_list, will confuse pwq->nr_active
1256                  * management later on and cause stall.  Make sure the work
1257                  * item is activated before grabbing.
1258                  */
1259                 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1260                         pwq_activate_delayed_work(work);
1261 
1262                 list_del_init(&work->entry);
1263                 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1264 
1265                 /* work->data points to pwq iff queued, point to pool */
1266                 set_work_pool_and_keep_pending(work, pool->id);
1267 
1268                 spin_unlock(&pool->lock);
1269                 return 1;
1270         }
1271         spin_unlock(&pool->lock);
1272 fail:
1273         local_irq_restore(*flags);
1274         if (work_is_canceling(work))
1275                 return -ENOENT;
1276         cpu_relax();
1277         return -EAGAIN;
1278 }
1279 
1280 /**
1281  * insert_work - insert a work into a pool
1282  * @pwq: pwq @work belongs to
1283  * @work: work to insert
1284  * @head: insertion point
1285  * @extra_flags: extra WORK_STRUCT_* flags to set
1286  *
1287  * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
1288  * work_struct flags.
1289  *
1290  * CONTEXT:
1291  * spin_lock_irq(pool->lock).
1292  */
1293 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1294                         struct list_head *head, unsigned int extra_flags)
1295 {
1296         struct worker_pool *pool = pwq->pool;
1297 
1298         /* we own @work, set data and link */
1299         set_work_pwq(work, pwq, extra_flags);
1300         list_add_tail(&work->entry, head);
1301         get_pwq(pwq);
1302 
1303         /*
1304          * Ensure either wq_worker_sleeping() sees the above
1305          * list_add_tail() or we see zero nr_running to avoid workers lying
1306          * around lazily while there are works to be processed.
1307          */
1308         smp_mb();
1309 
1310         if (__need_more_worker(pool))
1311                 wake_up_worker(pool);
1312 }
1313 
1314 /*
1315  * Test whether @work is being queued from another work executing on the
1316  * same workqueue.
1317  */
1318 static bool is_chained_work(struct workqueue_struct *wq)
1319 {
1320         struct worker *worker;
1321 
1322         worker = current_wq_worker();
1323         /*
1324          * Return %true iff I'm a worker execuing a work item on @wq.  If
1325          * I'm @worker, it's safe to dereference it without locking.
1326          */
1327         return worker && worker->current_pwq->wq == wq;
1328 }
1329 
1330 /*
1331  * When queueing an unbound work item to a wq, prefer local CPU if allowed
1332  * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
1333  * avoid perturbing sensitive tasks.
1334  */
1335 static int wq_select_unbound_cpu(int cpu)
1336 {
1337         static bool printed_dbg_warning;
1338         int new_cpu;
1339 
1340         if (likely(!wq_debug_force_rr_cpu)) {
1341                 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1342                         return cpu;
1343         } else if (!printed_dbg_warning) {
1344                 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1345                 printed_dbg_warning = true;
1346         }
1347 
1348         if (cpumask_empty(wq_unbound_cpumask))
1349                 return cpu;
1350 
1351         new_cpu = __this_cpu_read(wq_rr_cpu_last);
1352         new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1353         if (unlikely(new_cpu >= nr_cpu_ids)) {
1354                 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1355                 if (unlikely(new_cpu >= nr_cpu_ids))
1356                         return cpu;
1357         }
1358         __this_cpu_write(wq_rr_cpu_last, new_cpu);
1359 
1360         return new_cpu;
1361 }
1362 
1363 static void __queue_work(int cpu, struct workqueue_struct *wq,
1364                          struct work_struct *work)
1365 {
1366         struct pool_workqueue *pwq;
1367         struct worker_pool *last_pool;
1368         struct list_head *worklist;
1369         unsigned int work_flags;
1370         unsigned int req_cpu = cpu;
1371 
1372         /*
1373          * While a work item is PENDING && off queue, a task trying to
1374          * steal the PENDING will busy-loop waiting for it to either get
1375          * queued or lose PENDING.  Grabbing PENDING and queueing should
1376          * happen with IRQ disabled.
1377          */
1378         WARN_ON_ONCE(!irqs_disabled());
1379 
1380         debug_work_activate(work);
1381 
1382         /* if draining, only works from the same workqueue are allowed */
1383         if (unlikely(wq->flags & __WQ_DRAINING) &&
1384             WARN_ON_ONCE(!is_chained_work(wq)))
1385                 return;
1386 retry:
1387         if (req_cpu == WORK_CPU_UNBOUND)
1388                 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1389 
1390         /* pwq which will be used unless @work is executing elsewhere */
1391         if (!(wq->flags & WQ_UNBOUND))
1392                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1393         else
1394                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1395 
1396         /*
1397          * If @work was previously on a different pool, it might still be
1398          * running there, in which case the work needs to be queued on that
1399          * pool to guarantee non-reentrancy.
1400          */
1401         last_pool = get_work_pool(work);
1402         if (last_pool && last_pool != pwq->pool) {
1403                 struct worker *worker;
1404 
1405                 spin_lock(&last_pool->lock);
1406 
1407                 worker = find_worker_executing_work(last_pool, work);
1408 
1409                 if (worker && worker->current_pwq->wq == wq) {
1410                         pwq = worker->current_pwq;
1411                 } else {
1412                         /* meh... not running there, queue here */
1413                         spin_unlock(&last_pool->lock);
1414                         spin_lock(&pwq->pool->lock);
1415                 }
1416         } else {
1417                 spin_lock(&pwq->pool->lock);
1418         }
1419 
1420         /*
1421          * pwq is determined and locked.  For unbound pools, we could have
1422          * raced with pwq release and it could already be dead.  If its
1423          * refcnt is zero, repeat pwq selection.  Note that pwqs never die
1424          * without another pwq replacing it in the numa_pwq_tbl or while
1425          * work items are executing on it, so the retrying is guaranteed to
1426          * make forward-progress.
1427          */
1428         if (unlikely(!pwq->refcnt)) {
1429                 if (wq->flags & WQ_UNBOUND) {
1430                         spin_unlock(&pwq->pool->lock);
1431                         cpu_relax();
1432                         goto retry;
1433                 }
1434                 /* oops */
1435                 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1436                           wq->name, cpu);
1437         }
1438 
1439         /* pwq determined, queue */
1440         trace_workqueue_queue_work(req_cpu, pwq, work);
1441 
1442         if (WARN_ON(!list_empty(&work->entry))) {
1443                 spin_unlock(&pwq->pool->lock);
1444                 return;
1445         }
1446 
1447         pwq->nr_in_flight[pwq->work_color]++;
1448         work_flags = work_color_to_flags(pwq->work_color);
1449 
1450         if (likely(pwq->nr_active < pwq->max_active)) {
1451                 trace_workqueue_activate_work(work);
1452                 pwq->nr_active++;
1453                 worklist = &pwq->pool->worklist;
1454                 if (list_empty(worklist))
1455                         pwq->pool->watchdog_ts = jiffies;
1456         } else {
1457                 work_flags |= WORK_STRUCT_DELAYED;
1458                 worklist = &pwq->delayed_works;
1459         }
1460 
1461         insert_work(pwq, work, worklist, work_flags);
1462 
1463         spin_unlock(&pwq->pool->lock);
1464 }
1465 
1466 /**
1467  * queue_work_on - queue work on specific cpu
1468  * @cpu: CPU number to execute work on
1469  * @wq: workqueue to use
1470  * @work: work to queue
1471  *
1472  * We queue the work to a specific CPU, the caller must ensure it
1473  * can't go away.
1474  *
1475  * Return: %false if @work was already on a queue, %true otherwise.
1476  */
1477 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1478                    struct work_struct *work)
1479 {
1480         bool ret = false;
1481         unsigned long flags;
1482 
1483         local_irq_save(flags);
1484 
1485         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1486                 __queue_work(cpu, wq, work);
1487                 ret = true;
1488         }
1489 
1490         local_irq_restore(flags);
1491         return ret;
1492 }
1493 EXPORT_SYMBOL(queue_work_on);
1494 
1495 void delayed_work_timer_fn(unsigned long __data)
1496 {
1497         struct delayed_work *dwork = (struct delayed_work *)__data;
1498 
1499         /* should have been called from irqsafe timer with irq already off */
1500         __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1501 }
1502 EXPORT_SYMBOL(delayed_work_timer_fn);
1503 
1504 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1505                                 struct delayed_work *dwork, unsigned long delay)
1506 {
1507         struct timer_list *timer = &dwork->timer;
1508         struct work_struct *work = &dwork->work;
1509 
1510         WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1511                      timer->data != (unsigned long)dwork);
1512         WARN_ON_ONCE(timer_pending(timer));
1513         WARN_ON_ONCE(!list_empty(&work->entry));
1514 
1515         /*
1516          * If @delay is 0, queue @dwork->work immediately.  This is for
1517          * both optimization and correctness.  The earliest @timer can
1518          * expire is on the closest next tick and delayed_work users depend
1519          * on that there's no such delay when @delay is 0.
1520          */
1521         if (!delay) {
1522                 __queue_work(cpu, wq, &dwork->work);
1523                 return;
1524         }
1525 
1526         timer_stats_timer_set_start_info(&dwork->timer);
1527 
1528         dwork->wq = wq;
1529         dwork->cpu = cpu;
1530         timer->expires = jiffies + delay;
1531 
1532         if (unlikely(cpu != WORK_CPU_UNBOUND))
1533                 add_timer_on(timer, cpu);
1534         else
1535                 add_timer(timer);
1536 }
1537 
1538 /**
1539  * queue_delayed_work_on - queue work on specific CPU after delay
1540  * @cpu: CPU number to execute work on
1541  * @wq: workqueue to use
1542  * @dwork: work to queue
1543  * @delay: number of jiffies to wait before queueing
1544  *
1545  * Return: %false if @work was already on a queue, %true otherwise.  If
1546  * @delay is zero and @dwork is idle, it will be scheduled for immediate
1547  * execution.
1548  */
1549 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1550                            struct delayed_work *dwork, unsigned long delay)
1551 {
1552         struct work_struct *work = &dwork->work;
1553         bool ret = false;
1554         unsigned long flags;
1555 
1556         /* read the comment in __queue_work() */
1557         local_irq_save(flags);
1558 
1559         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1560                 __queue_delayed_work(cpu, wq, dwork, delay);
1561                 ret = true;
1562         }
1563 
1564         local_irq_restore(flags);
1565         return ret;
1566 }
1567 EXPORT_SYMBOL(queue_delayed_work_on);
1568 
1569 /**
1570  * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1571  * @cpu: CPU number to execute work on
1572  * @wq: workqueue to use
1573  * @dwork: work to queue
1574  * @delay: number of jiffies to wait before queueing
1575  *
1576  * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1577  * modify @dwork's timer so that it expires after @delay.  If @delay is
1578  * zero, @work is guaranteed to be scheduled immediately regardless of its
1579  * current state.
1580  *
1581  * Return: %false if @dwork was idle and queued, %true if @dwork was
1582  * pending and its timer was modified.
1583  *
1584  * This function is safe to call from any context including IRQ handler.
1585  * See try_to_grab_pending() for details.
1586  */
1587 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1588                          struct delayed_work *dwork, unsigned long delay)
1589 {
1590         unsigned long flags;
1591         int ret;
1592 
1593         do {
1594                 ret = try_to_grab_pending(&dwork->work, true, &flags);
1595         } while (unlikely(ret == -EAGAIN));
1596 
1597         if (likely(ret >= 0)) {
1598                 __queue_delayed_work(cpu, wq, dwork, delay);
1599                 local_irq_restore(flags);
1600         }
1601 
1602         /* -ENOENT from try_to_grab_pending() becomes %true */
1603         return ret;
1604 }
1605 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1606 
1607 /**
1608  * worker_enter_idle - enter idle state
1609  * @worker: worker which is entering idle state
1610  *
1611  * @worker is entering idle state.  Update stats and idle timer if
1612  * necessary.
1613  *
1614  * LOCKING:
1615  * spin_lock_irq(pool->lock).
1616  */
1617 static void worker_enter_idle(struct worker *worker)
1618 {
1619         struct worker_pool *pool = worker->pool;
1620 
1621         if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1622             WARN_ON_ONCE(!list_empty(&worker->entry) &&
1623                          (worker->hentry.next || worker->hentry.pprev)))
1624                 return;
1625 
1626         /* can't use worker_set_flags(), also called from create_worker() */
1627         worker->flags |= WORKER_IDLE;
1628         pool->nr_idle++;
1629         worker->last_active = jiffies;
1630 
1631         /* idle_list is LIFO */
1632         list_add(&worker->entry, &pool->idle_list);
1633 
1634         if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1635                 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1636 
1637         /*
1638          * Sanity check nr_running.  Because wq_unbind_fn() releases
1639          * pool->lock between setting %WORKER_UNBOUND and zapping
1640          * nr_running, the warning may trigger spuriously.  Check iff
1641          * unbind is not in progress.
1642          */
1643         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1644                      pool->nr_workers == pool->nr_idle &&
1645                      atomic_read(&pool->nr_running));
1646 }
1647 
1648 /**
1649  * worker_leave_idle - leave idle state
1650  * @worker: worker which is leaving idle state
1651  *
1652  * @worker is leaving idle state.  Update stats.
1653  *
1654  * LOCKING:
1655  * spin_lock_irq(pool->lock).
1656  */
1657 static void worker_leave_idle(struct worker *worker)
1658 {
1659         struct worker_pool *pool = worker->pool;
1660 
1661         if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1662                 return;
1663         worker_clr_flags(worker, WORKER_IDLE);
1664         pool->nr_idle--;
1665         list_del_init(&worker->entry);
1666 }
1667 
1668 static struct worker *alloc_worker(int node)
1669 {
1670         struct worker *worker;
1671 
1672         worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1673         if (worker) {
1674                 INIT_LIST_HEAD(&worker->entry);
1675                 INIT_LIST_HEAD(&worker->scheduled);
1676                 INIT_LIST_HEAD(&worker->node);
1677                 /* on creation a worker is in !idle && prep state */
1678                 worker->flags = WORKER_PREP;
1679         }
1680         return worker;
1681 }
1682 
1683 /**
1684  * worker_attach_to_pool() - attach a worker to a pool
1685  * @worker: worker to be attached
1686  * @pool: the target pool
1687  *
1688  * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
1689  * cpu-binding of @worker are kept coordinated with the pool across
1690  * cpu-[un]hotplugs.
1691  */
1692 static void worker_attach_to_pool(struct worker *worker,
1693                                    struct worker_pool *pool)
1694 {
1695         mutex_lock(&pool->attach_mutex);
1696 
1697         /*
1698          * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1699          * online CPUs.  It'll be re-applied when any of the CPUs come up.
1700          */
1701         set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1702 
1703         /*
1704          * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1705          * stable across this function.  See the comments above the
1706          * flag definition for details.
1707          */
1708         if (pool->flags & POOL_DISASSOCIATED)
1709                 worker->flags |= WORKER_UNBOUND;
1710 
1711         list_add_tail(&worker->node, &pool->workers);
1712 
1713         mutex_unlock(&pool->attach_mutex);
1714 }
1715 
1716 /**
1717  * worker_detach_from_pool() - detach a worker from its pool
1718  * @worker: worker which is attached to its pool
1719  * @pool: the pool @worker is attached to
1720  *
1721  * Undo the attaching which had been done in worker_attach_to_pool().  The
1722  * caller worker shouldn't access to the pool after detached except it has
1723  * other reference to the pool.
1724  */
1725 static void worker_detach_from_pool(struct worker *worker,
1726                                     struct worker_pool *pool)
1727 {
1728         struct completion *detach_completion = NULL;
1729 
1730         mutex_lock(&pool->attach_mutex);
1731         list_del(&worker->node);
1732         if (list_empty(&pool->workers))
1733                 detach_completion = pool->detach_completion;
1734         mutex_unlock(&pool->attach_mutex);
1735 
1736         /* clear leftover flags without pool->lock after it is detached */
1737         worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1738 
1739         if (detach_completion)
1740                 complete(detach_completion);
1741 }
1742 
1743 /**
1744  * create_worker - create a new workqueue worker
1745  * @pool: pool the new worker will belong to
1746  *
1747  * Create and start a new worker which is attached to @pool.
1748  *
1749  * CONTEXT:
1750  * Might sleep.  Does GFP_KERNEL allocations.
1751  *
1752  * Return:
1753  * Pointer to the newly created worker.
1754  */
1755 static struct worker *create_worker(struct worker_pool *pool)
1756 {
1757         struct worker *worker = NULL;
1758         int id = -1;
1759         char id_buf[16];
1760 
1761         /* ID is needed to determine kthread name */
1762         id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1763         if (id < 0)
1764                 goto fail;
1765 
1766         worker = alloc_worker(pool->node);
1767         if (!worker)
1768                 goto fail;
1769 
1770         worker->pool = pool;
1771         worker->id = id;
1772 
1773         if (pool->cpu >= 0)
1774                 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1775                          pool->attrs->nice < 0  ? "H" : "");
1776         else
1777                 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1778 
1779         worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1780                                               "kworker/%s", id_buf);
1781         if (IS_ERR(worker->task))
1782                 goto fail;
1783 
1784         set_user_nice(worker->task, pool->attrs->nice);
1785         kthread_bind_mask(worker->task, pool->attrs->cpumask);
1786 
1787         /* successful, attach the worker to the pool */
1788         worker_attach_to_pool(worker, pool);
1789 
1790         /* start the newly created worker */
1791         spin_lock_irq(&pool->lock);
1792         worker->pool->nr_workers++;
1793         worker_enter_idle(worker);
1794         wake_up_process(worker->task);
1795         spin_unlock_irq(&pool->lock);
1796 
1797         return worker;
1798 
1799 fail:
1800         if (id >= 0)
1801                 ida_simple_remove(&pool->worker_ida, id);
1802         kfree(worker);
1803         return NULL;
1804 }
1805 
1806 /**
1807  * destroy_worker - destroy a workqueue worker
1808  * @worker: worker to be destroyed
1809  *
1810  * Destroy @worker and adjust @pool stats accordingly.  The worker should
1811  * be idle.
1812  *
1813  * CONTEXT:
1814  * spin_lock_irq(pool->lock).
1815  */
1816 static void destroy_worker(struct worker *worker)
1817 {
1818         struct worker_pool *pool = worker->pool;
1819 
1820         lockdep_assert_held(&pool->lock);
1821 
1822         /* sanity check frenzy */
1823         if (WARN_ON(worker->current_work) ||
1824             WARN_ON(!list_empty(&worker->scheduled)) ||
1825             WARN_ON(!(worker->flags & WORKER_IDLE)))
1826                 return;
1827 
1828         pool->nr_workers--;
1829         pool->nr_idle--;
1830 
1831         list_del_init(&worker->entry);
1832         worker->flags |= WORKER_DIE;
1833         wake_up_process(worker->task);
1834 }
1835 
1836 static void idle_worker_timeout(unsigned long __pool)
1837 {
1838         struct worker_pool *pool = (void *)__pool;
1839 
1840         spin_lock_irq(&pool->lock);
1841 
1842         while (too_many_workers(pool)) {
1843                 struct worker *worker;
1844                 unsigned long expires;
1845 
1846                 /* idle_list is kept in LIFO order, check the last one */
1847                 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1848                 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1849 
1850                 if (time_before(jiffies, expires)) {
1851                         mod_timer(&pool->idle_timer, expires);
1852                         break;
1853                 }
1854 
1855                 destroy_worker(worker);
1856         }
1857 
1858         spin_unlock_irq(&pool->lock);
1859 }
1860 
1861 static void send_mayday(struct work_struct *work)
1862 {
1863         struct pool_workqueue *pwq = get_work_pwq(work);
1864         struct workqueue_struct *wq = pwq->wq;
1865 
1866         lockdep_assert_held(&wq_mayday_lock);
1867 
1868         if (!wq->rescuer)
1869                 return;
1870 
1871         /* mayday mayday mayday */
1872         if (list_empty(&pwq->mayday_node)) {
1873                 /*
1874                  * If @pwq is for an unbound wq, its base ref may be put at
1875                  * any time due to an attribute change.  Pin @pwq until the
1876                  * rescuer is done with it.
1877                  */
1878                 get_pwq(pwq);
1879                 list_add_tail(&pwq->mayday_node, &wq->maydays);
1880                 wake_up_process(wq->rescuer->task);
1881         }
1882 }
1883 
1884 static void pool_mayday_timeout(unsigned long __pool)
1885 {
1886         struct worker_pool *pool = (void *)__pool;
1887         struct work_struct *work;
1888 
1889         spin_lock_irq(&pool->lock);
1890         spin_lock(&wq_mayday_lock);             /* for wq->maydays */
1891 
1892         if (need_to_create_worker(pool)) {
1893                 /*
1894                  * We've been trying to create a new worker but
1895                  * haven't been successful.  We might be hitting an
1896                  * allocation deadlock.  Send distress signals to
1897                  * rescuers.
1898                  */
1899                 list_for_each_entry(work, &pool->worklist, entry)
1900                         send_mayday(work);
1901         }
1902 
1903         spin_unlock(&wq_mayday_lock);
1904         spin_unlock_irq(&pool->lock);
1905 
1906         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1907 }
1908 
1909 /**
1910  * maybe_create_worker - create a new worker if necessary
1911  * @pool: pool to create a new worker for
1912  *
1913  * Create a new worker for @pool if necessary.  @pool is guaranteed to
1914  * have at least one idle worker on return from this function.  If
1915  * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1916  * sent to all rescuers with works scheduled on @pool to resolve
1917  * possible allocation deadlock.
1918  *
1919  * On return, need_to_create_worker() is guaranteed to be %false and
1920  * may_start_working() %true.
1921  *
1922  * LOCKING:
1923  * spin_lock_irq(pool->lock) which may be released and regrabbed
1924  * multiple times.  Does GFP_KERNEL allocations.  Called only from
1925  * manager.
1926  */
1927 static void maybe_create_worker(struct worker_pool *pool)
1928 __releases(&pool->lock)
1929 __acquires(&pool->lock)
1930 {
1931 restart:
1932         spin_unlock_irq(&pool->lock);
1933 
1934         /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1935         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1936 
1937         while (true) {
1938                 if (create_worker(pool) || !need_to_create_worker(pool))
1939                         break;
1940 
1941                 schedule_timeout_interruptible(CREATE_COOLDOWN);
1942 
1943                 if (!need_to_create_worker(pool))
1944                         break;
1945         }
1946 
1947         del_timer_sync(&pool->mayday_timer);
1948         spin_lock_irq(&pool->lock);
1949         /*
1950          * This is necessary even after a new worker was just successfully
1951          * created as @pool->lock was dropped and the new worker might have
1952          * already become busy.
1953          */
1954         if (need_to_create_worker(pool))
1955                 goto restart;
1956 }
1957 
1958 /**
1959  * manage_workers - manage worker pool
1960  * @worker: self
1961  *
1962  * Assume the manager role and manage the worker pool @worker belongs
1963  * to.  At any given time, there can be only zero or one manager per
1964  * pool.  The exclusion is handled automatically by this function.
1965  *
1966  * The caller can safely start processing works on false return.  On
1967  * true return, it's guaranteed that need_to_create_worker() is false
1968  * and may_start_working() is true.
1969  *
1970  * CONTEXT:
1971  * spin_lock_irq(pool->lock) which may be released and regrabbed
1972  * multiple times.  Does GFP_KERNEL allocations.
1973  *
1974  * Return:
1975  * %false if the pool doesn't need management and the caller can safely
1976  * start processing works, %true if management function was performed and
1977  * the conditions that the caller verified before calling the function may
1978  * no longer be true.
1979  */
1980 static bool manage_workers(struct worker *worker)
1981 {
1982         struct worker_pool *pool = worker->pool;
1983 
1984         /*
1985          * Anyone who successfully grabs manager_arb wins the arbitration
1986          * and becomes the manager.  mutex_trylock() on pool->manager_arb
1987          * failure while holding pool->lock reliably indicates that someone
1988          * else is managing the pool and the worker which failed trylock
1989          * can proceed to executing work items.  This means that anyone
1990          * grabbing manager_arb is responsible for actually performing
1991          * manager duties.  If manager_arb is grabbed and released without
1992          * actual management, the pool may stall indefinitely.
1993          */
1994         if (!mutex_trylock(&pool->manager_arb))
1995                 return false;
1996         pool->manager = worker;
1997 
1998         maybe_create_worker(pool);
1999 
2000         pool->manager = NULL;
2001         mutex_unlock(&pool->manager_arb);
2002         return true;
2003 }
2004 
2005 /**
2006  * process_one_work - process single work
2007  * @worker: self
2008  * @work: work to process
2009  *
2010  * Process @work.  This function contains all the logics necessary to
2011  * process a single work including synchronization against and
2012  * interaction with other workers on the same cpu, queueing and
2013  * flushing.  As long as context requirement is met, any worker can
2014  * call this function to process a work.
2015  *
2016  * CONTEXT:
2017  * spin_lock_irq(pool->lock) which is released and regrabbed.
2018  */
2019 static void process_one_work(struct worker *worker, struct work_struct *work)
2020 __releases(&pool->lock)
2021 __acquires(&pool->lock)
2022 {
2023         struct pool_workqueue *pwq = get_work_pwq(work);
2024         struct worker_pool *pool = worker->pool;
2025         bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2026         int work_color;
2027         struct worker *collision;
2028 #ifdef CONFIG_LOCKDEP
2029         /*
2030          * It is permissible to free the struct work_struct from
2031          * inside the function that is called from it, this we need to
2032          * take into account for lockdep too.  To avoid bogus "held
2033          * lock freed" warnings as well as problems when looking into
2034          * work->lockdep_map, make a copy and use that here.
2035          */
2036         struct lockdep_map lockdep_map;
2037 
2038         lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2039 #endif
2040         /* ensure we're on the correct CPU */
2041         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2042                      raw_smp_processor_id() != pool->cpu);
2043 
2044         /*
2045          * A single work shouldn't be executed concurrently by
2046          * multiple workers on a single cpu.  Check whether anyone is
2047          * already processing the work.  If so, defer the work to the
2048          * currently executing one.
2049          */
2050         collision = find_worker_executing_work(pool, work);
2051         if (unlikely(collision)) {
2052                 move_linked_works(work, &collision->scheduled, NULL);
2053                 return;
2054         }
2055 
2056         /* claim and dequeue */
2057         debug_work_deactivate(work);
2058         hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2059         worker->current_work = work;
2060         worker->current_func = work->func;
2061         worker->current_pwq = pwq;
2062         work_color = get_work_color(work);
2063 
2064         list_del_init(&work->entry);
2065 
2066         /*
2067          * CPU intensive works don't participate in concurrency management.
2068          * They're the scheduler's responsibility.  This takes @worker out
2069          * of concurrency management and the next code block will chain
2070          * execution of the pending work items.
2071          */
2072         if (unlikely(cpu_intensive))
2073                 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2074 
2075         /*
2076          * Wake up another worker if necessary.  The condition is always
2077          * false for normal per-cpu workers since nr_running would always
2078          * be >= 1 at this point.  This is used to chain execution of the
2079          * pending work items for WORKER_NOT_RUNNING workers such as the
2080          * UNBOUND and CPU_INTENSIVE ones.
2081          */
2082         if (need_more_worker(pool))
2083                 wake_up_worker(pool);
2084 
2085         /*
2086          * Record the last pool and clear PENDING which should be the last
2087          * update to @work.  Also, do this inside @pool->lock so that
2088          * PENDING and queued state changes happen together while IRQ is
2089          * disabled.
2090          */
2091         set_work_pool_and_clear_pending(work, pool->id);
2092 
2093         spin_unlock_irq(&pool->lock);
2094 
2095         lock_map_acquire_read(&pwq->wq->lockdep_map);
2096         lock_map_acquire(&lockdep_map);
2097         trace_workqueue_execute_start(work);
2098         worker->current_func(work);
2099         /*
2100          * While we must be careful to not use "work" after this, the trace
2101          * point will only record its address.
2102          */
2103         trace_workqueue_execute_end(work);
2104         lock_map_release(&lockdep_map);
2105         lock_map_release(&pwq->wq->lockdep_map);
2106 
2107         if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2108                 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2109                        "     last function: %pf\n",
2110                        current->comm, preempt_count(), task_pid_nr(current),
2111                        worker->current_func);
2112                 debug_show_held_locks(current);
2113                 dump_stack();
2114         }
2115 
2116         /*
2117          * The following prevents a kworker from hogging CPU on !PREEMPT
2118          * kernels, where a requeueing work item waiting for something to
2119          * happen could deadlock with stop_machine as such work item could
2120          * indefinitely requeue itself while all other CPUs are trapped in
2121          * stop_machine. At the same time, report a quiescent RCU state so
2122          * the same condition doesn't freeze RCU.
2123          */
2124         cond_resched_rcu_qs();
2125 
2126         spin_lock_irq(&pool->lock);
2127 
2128         /* clear cpu intensive status */
2129         if (unlikely(cpu_intensive))
2130                 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2131 
2132         /* we're done with it, release */
2133         hash_del(&worker->hentry);
2134         worker->current_work = NULL;
2135         worker->current_func = NULL;
2136         worker->current_pwq = NULL;
2137         worker->desc_valid = false;
2138         pwq_dec_nr_in_flight(pwq, work_color);
2139 }
2140 
2141 /**
2142  * process_scheduled_works - process scheduled works
2143  * @worker: self
2144  *
2145  * Process all scheduled works.  Please note that the scheduled list
2146  * may change while processing a work, so this function repeatedly
2147  * fetches a work from the top and executes it.
2148  *
2149  * CONTEXT:
2150  * spin_lock_irq(pool->lock) which may be released and regrabbed
2151  * multiple times.
2152  */
2153 static void process_scheduled_works(struct worker *worker)
2154 {
2155         while (!list_empty(&worker->scheduled)) {
2156                 struct work_struct *work = list_first_entry(&worker->scheduled,
2157                                                 struct work_struct, entry);
2158                 process_one_work(worker, work);
2159         }
2160 }
2161 
2162 /**
2163  * worker_thread - the worker thread function
2164  * @__worker: self
2165  *
2166  * The worker thread function.  All workers belong to a worker_pool -
2167  * either a per-cpu one or dynamic unbound one.  These workers process all
2168  * work items regardless of their specific target workqueue.  The only
2169  * exception is work items which belong to workqueues with a rescuer which
2170  * will be explained in rescuer_thread().
2171  *
2172  * Return: 0
2173  */
2174 static int worker_thread(void *__worker)
2175 {
2176         struct worker *worker = __worker;
2177         struct worker_pool *pool = worker->pool;
2178 
2179         /* tell the scheduler that this is a workqueue worker */
2180         worker->task->flags |= PF_WQ_WORKER;
2181 woke_up:
2182         spin_lock_irq(&pool->lock);
2183 
2184         /* am I supposed to die? */
2185         if (unlikely(worker->flags & WORKER_DIE)) {
2186                 spin_unlock_irq(&pool->lock);
2187                 WARN_ON_ONCE(!list_empty(&worker->entry));
2188                 worker->task->flags &= ~PF_WQ_WORKER;
2189 
2190                 set_task_comm(worker->task, "kworker/dying");
2191                 ida_simple_remove(&pool->worker_ida, worker->id);
2192                 worker_detach_from_pool(worker, pool);
2193                 kfree(worker);
2194                 return 0;
2195         }
2196 
2197         worker_leave_idle(worker);
2198 recheck:
2199         /* no more worker necessary? */
2200         if (!need_more_worker(pool))
2201                 goto sleep;
2202 
2203         /* do we need to manage? */
2204         if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2205                 goto recheck;
2206 
2207         /*
2208          * ->scheduled list can only be filled while a worker is
2209          * preparing to process a work or actually processing it.
2210          * Make sure nobody diddled with it while I was sleeping.
2211          */
2212         WARN_ON_ONCE(!list_empty(&worker->scheduled));
2213 
2214         /*
2215          * Finish PREP stage.  We're guaranteed to have at least one idle
2216          * worker or that someone else has already assumed the manager
2217          * role.  This is where @worker starts participating in concurrency
2218          * management if applicable and concurrency management is restored
2219          * after being rebound.  See rebind_workers() for details.
2220          */
2221         worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2222 
2223         do {
2224                 struct work_struct *work =
2225                         list_first_entry(&pool->worklist,
2226                                          struct work_struct, entry);
2227 
2228                 pool->watchdog_ts = jiffies;
2229 
2230                 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2231                         /* optimization path, not strictly necessary */
2232                         process_one_work(worker, work);
2233                         if (unlikely(!list_empty(&worker->scheduled)))
2234                                 process_scheduled_works(worker);
2235                 } else {
2236                         move_linked_works(work, &worker->scheduled, NULL);
2237                         process_scheduled_works(worker);
2238                 }
2239         } while (keep_working(pool));
2240 
2241         worker_set_flags(worker, WORKER_PREP);
2242 sleep:
2243         /*
2244          * pool->lock is held and there's no work to process and no need to
2245          * manage, sleep.  Workers are woken up only while holding
2246          * pool->lock or from local cpu, so setting the current state
2247          * before releasing pool->lock is enough to prevent losing any
2248          * event.
2249          */
2250         worker_enter_idle(worker);
2251         __set_current_state(TASK_INTERRUPTIBLE);
2252         spin_unlock_irq(&pool->lock);
2253         schedule();
2254         goto woke_up;
2255 }
2256 
2257 /**
2258  * rescuer_thread - the rescuer thread function
2259  * @__rescuer: self
2260  *
2261  * Workqueue rescuer thread function.  There's one rescuer for each
2262  * workqueue which has WQ_MEM_RECLAIM set.
2263  *
2264  * Regular work processing on a pool may block trying to create a new
2265  * worker which uses GFP_KERNEL allocation which has slight chance of
2266  * developing into deadlock if some works currently on the same queue
2267  * need to be processed to satisfy the GFP_KERNEL allocation.  This is
2268  * the problem rescuer solves.
2269  *
2270  * When such condition is possible, the pool summons rescuers of all
2271  * workqueues which have works queued on the pool and let them process
2272  * those works so that forward progress can be guaranteed.
2273  *
2274  * This should happen rarely.
2275  *
2276  * Return: 0
2277  */
2278 static int rescuer_thread(void *__rescuer)
2279 {
2280         struct worker *rescuer = __rescuer;
2281         struct workqueue_struct *wq = rescuer->rescue_wq;
2282         struct list_head *scheduled = &rescuer->scheduled;
2283         bool should_stop;
2284 
2285         set_user_nice(current, RESCUER_NICE_LEVEL);
2286 
2287         /*
2288          * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
2289          * doesn't participate in concurrency management.
2290          */
2291         rescuer->task->flags |= PF_WQ_WORKER;
2292 repeat:
2293         set_current_state(TASK_INTERRUPTIBLE);
2294 
2295         /*
2296          * By the time the rescuer is requested to stop, the workqueue
2297          * shouldn't have any work pending, but @wq->maydays may still have
2298          * pwq(s) queued.  This can happen by non-rescuer workers consuming
2299          * all the work items before the rescuer got to them.  Go through
2300          * @wq->maydays processing before acting on should_stop so that the
2301          * list is always empty on exit.
2302          */
2303         should_stop = kthread_should_stop();
2304 
2305         /* see whether any pwq is asking for help */
2306         spin_lock_irq(&wq_mayday_lock);
2307 
2308         while (!list_empty(&wq->maydays)) {
2309                 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2310                                         struct pool_workqueue, mayday_node);
2311                 struct worker_pool *pool = pwq->pool;
2312                 struct work_struct *work, *n;
2313                 bool first = true;
2314 
2315                 __set_current_state(TASK_RUNNING);
2316                 list_del_init(&pwq->mayday_node);
2317 
2318                 spin_unlock_irq(&wq_mayday_lock);
2319 
2320                 worker_attach_to_pool(rescuer, pool);
2321 
2322                 spin_lock_irq(&pool->lock);
2323                 rescuer->pool = pool;
2324 
2325                 /*
2326                  * Slurp in all works issued via this workqueue and
2327                  * process'em.
2328                  */
2329                 WARN_ON_ONCE(!list_empty(scheduled));
2330                 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2331                         if (get_work_pwq(work) == pwq) {
2332                                 if (first)
2333                                         pool->watchdog_ts = jiffies;
2334                                 move_linked_works(work, scheduled, &n);
2335                         }
2336                         first = false;
2337                 }
2338 
2339                 if (!list_empty(scheduled)) {
2340                         process_scheduled_works(rescuer);
2341 
2342                         /*
2343                          * The above execution of rescued work items could
2344                          * have created more to rescue through
2345                          * pwq_activate_first_delayed() or chained
2346                          * queueing.  Let's put @pwq back on mayday list so
2347                          * that such back-to-back work items, which may be
2348                          * being used to relieve memory pressure, don't
2349                          * incur MAYDAY_INTERVAL delay inbetween.
2350                          */
2351                         if (need_to_create_worker(pool)) {
2352                                 spin_lock(&wq_mayday_lock);
2353                                 get_pwq(pwq);
2354                                 list_move_tail(&pwq->mayday_node, &wq->maydays);
2355                                 spin_unlock(&wq_mayday_lock);
2356                         }
2357                 }
2358 
2359                 /*
2360                  * Put the reference grabbed by send_mayday().  @pool won't
2361                  * go away while we're still attached to it.
2362                  */
2363                 put_pwq(pwq);
2364 
2365                 /*
2366                  * Leave this pool.  If need_more_worker() is %true, notify a
2367                  * regular worker; otherwise, we end up with 0 concurrency
2368                  * and stalling the execution.
2369                  */
2370                 if (need_more_worker(pool))
2371                         wake_up_worker(pool);
2372 
2373                 rescuer->pool = NULL;
2374                 spin_unlock_irq(&pool->lock);
2375 
2376                 worker_detach_from_pool(rescuer, pool);
2377 
2378                 spin_lock_irq(&wq_mayday_lock);
2379         }
2380 
2381         spin_unlock_irq(&wq_mayday_lock);
2382 
2383         if (should_stop) {
2384                 __set_current_state(TASK_RUNNING);
2385                 rescuer->task->flags &= ~PF_WQ_WORKER;
2386                 return 0;
2387         }
2388 
2389         /* rescuers should never participate in concurrency management */
2390         WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2391         schedule();
2392         goto repeat;
2393 }
2394 
2395 /**
2396  * check_flush_dependency - check for flush dependency sanity
2397  * @target_wq: workqueue being flushed
2398  * @target_work: work item being flushed (NULL for workqueue flushes)
2399  *
2400  * %current is trying to flush the whole @target_wq or @target_work on it.
2401  * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2402  * reclaiming memory or running on a workqueue which doesn't have
2403  * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2404  * a deadlock.
2405  */
2406 static void check_flush_dependency(struct workqueue_struct *target_wq,
2407                                    struct work_struct *target_work)
2408 {
2409         work_func_t target_func = target_work ? target_work->func : NULL;
2410         struct worker *worker;
2411 
2412         if (target_wq->flags & WQ_MEM_RECLAIM)
2413                 return;
2414 
2415         worker = current_wq_worker();
2416 
2417         WARN_ONCE(current->flags & PF_MEMALLOC,
2418                   "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2419                   current->pid, current->comm, target_wq->name, target_func);
2420         WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2421                               (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2422                   "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2423                   worker->current_pwq->wq->name, worker->current_func,
2424                   target_wq->name, target_func);
2425 }
2426 
2427 struct wq_barrier {
2428         struct work_struct      work;
2429         struct completion       done;
2430         struct task_struct      *task;  /* purely informational */
2431 };
2432 
2433 static void wq_barrier_func(struct work_struct *work)
2434 {
2435         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2436         complete(&barr->done);
2437 }
2438 
2439 /**
2440  * insert_wq_barrier - insert a barrier work
2441  * @pwq: pwq to insert barrier into
2442  * @barr: wq_barrier to insert
2443  * @target: target work to attach @barr to
2444  * @worker: worker currently executing @target, NULL if @target is not executing
2445  *
2446  * @barr is linked to @target such that @barr is completed only after
2447  * @target finishes execution.  Please note that the ordering
2448  * guarantee is observed only with respect to @target and on the local
2449  * cpu.
2450  *
2451  * Currently, a queued barrier can't be canceled.  This is because
2452  * try_to_grab_pending() can't determine whether the work to be
2453  * grabbed is at the head of the queue and thus can't clear LINKED
2454  * flag of the previous work while there must be a valid next work
2455  * after a work with LINKED flag set.
2456  *
2457  * Note that when @worker is non-NULL, @target may be modified
2458  * underneath us, so we can't reliably determine pwq from @target.
2459  *
2460  * CONTEXT:
2461  * spin_lock_irq(pool->lock).
2462  */
2463 static void insert_wq_barrier(struct pool_workqueue *pwq,
2464                               struct wq_barrier *barr,
2465                               struct work_struct *target, struct worker *worker)
2466 {
2467         struct list_head *head;
2468         unsigned int linked = 0;
2469 
2470         /*
2471          * debugobject calls are safe here even with pool->lock locked
2472          * as we know for sure that this will not trigger any of the
2473          * checks and call back into the fixup functions where we
2474          * might deadlock.
2475          */
2476         INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2477         __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2478         init_completion(&barr->done);
2479         barr->task = current;
2480 
2481         /*
2482          * If @target is currently being executed, schedule the
2483          * barrier to the worker; otherwise, put it after @target.
2484          */
2485         if (worker)
2486                 head = worker->scheduled.next;
2487         else {
2488                 unsigned long *bits = work_data_bits(target);
2489 
2490                 head = target->entry.next;
2491                 /* there can already be other linked works, inherit and set */
2492                 linked = *bits & WORK_STRUCT_LINKED;
2493                 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2494         }
2495 
2496         debug_work_activate(&barr->work);
2497         insert_work(pwq, &barr->work, head,
2498                     work_color_to_flags(WORK_NO_COLOR) | linked);
2499 }
2500 
2501 /**
2502  * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2503  * @wq: workqueue being flushed
2504  * @flush_color: new flush color, < 0 for no-op
2505  * @work_color: new work color, < 0 for no-op
2506  *
2507  * Prepare pwqs for workqueue flushing.
2508  *
2509  * If @flush_color is non-negative, flush_color on all pwqs should be
2510  * -1.  If no pwq has in-flight commands at the specified color, all
2511  * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
2512  * has in flight commands, its pwq->flush_color is set to
2513  * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2514  * wakeup logic is armed and %true is returned.
2515  *
2516  * The caller should have initialized @wq->first_flusher prior to
2517  * calling this function with non-negative @flush_color.  If
2518  * @flush_color is negative, no flush color update is done and %false
2519  * is returned.
2520  *
2521  * If @work_color is non-negative, all pwqs should have the same
2522  * work_color which is previous to @work_color and all will be
2523  * advanced to @work_color.
2524  *
2525  * CONTEXT:
2526  * mutex_lock(wq->mutex).
2527  *
2528  * Return:
2529  * %true if @flush_color >= 0 and there's something to flush.  %false
2530  * otherwise.
2531  */
2532 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2533                                       int flush_color, int work_color)
2534 {
2535         bool wait = false;
2536         struct pool_workqueue *pwq;
2537 
2538         if (flush_color >= 0) {
2539                 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2540                 atomic_set(&wq->nr_pwqs_to_flush, 1);
2541         }
2542 
2543         for_each_pwq(pwq, wq) {
2544                 struct worker_pool *pool = pwq->pool;
2545 
2546                 spin_lock_irq(&pool->lock);
2547 
2548                 if (flush_color >= 0) {
2549                         WARN_ON_ONCE(pwq->flush_color != -1);
2550 
2551                         if (pwq->nr_in_flight[flush_color]) {
2552                                 pwq->flush_color = flush_color;
2553                                 atomic_inc(&wq->nr_pwqs_to_flush);
2554                                 wait = true;
2555                         }
2556                 }
2557 
2558                 if (work_color >= 0) {
2559                         WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2560                         pwq->work_color = work_color;
2561                 }
2562 
2563                 spin_unlock_irq(&pool->lock);
2564         }
2565 
2566         if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2567                 complete(&wq->first_flusher->done);
2568 
2569         return wait;
2570 }
2571 
2572 /**
2573  * flush_workqueue - ensure that any scheduled work has run to completion.
2574  * @wq: workqueue to flush
2575  *
2576  * This function sleeps until all work items which were queued on entry
2577  * have finished execution, but it is not livelocked by new incoming ones.
2578  */
2579 void flush_workqueue(struct workqueue_struct *wq)
2580 {
2581         struct wq_flusher this_flusher = {
2582                 .list = LIST_HEAD_INIT(this_flusher.list),
2583                 .flush_color = -1,
2584                 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2585         };
2586         int next_color;
2587 
2588         if (WARN_ON(!wq_online))
2589                 return;
2590 
2591         lock_map_acquire(&wq->lockdep_map);
2592         lock_map_release(&wq->lockdep_map);
2593 
2594         mutex_lock(&wq->mutex);
2595 
2596         /*
2597          * Start-to-wait phase
2598          */
2599         next_color = work_next_color(wq->work_color);
2600 
2601         if (next_color != wq->flush_color) {
2602                 /*
2603                  * Color space is not full.  The current work_color
2604                  * becomes our flush_color and work_color is advanced
2605                  * by one.
2606                  */
2607                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2608                 this_flusher.flush_color = wq->work_color;
2609                 wq->work_color = next_color;
2610 
2611                 if (!wq->first_flusher) {
2612                         /* no flush in progress, become the first flusher */
2613                         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2614 
2615                         wq->first_flusher = &this_flusher;
2616 
2617                         if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2618                                                        wq->work_color)) {
2619                                 /* nothing to flush, done */
2620                                 wq->flush_color = next_color;
2621                                 wq->first_flusher = NULL;
2622                                 goto out_unlock;
2623                         }
2624                 } else {
2625                         /* wait in queue */
2626                         WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2627                         list_add_tail(&this_flusher.list, &wq->flusher_queue);
2628                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2629                 }
2630         } else {
2631                 /*
2632                  * Oops, color space is full, wait on overflow queue.
2633                  * The next flush completion will assign us
2634                  * flush_color and transfer to flusher_queue.
2635                  */
2636                 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2637         }
2638 
2639         check_flush_dependency(wq, NULL);
2640 
2641         mutex_unlock(&wq->mutex);
2642 
2643         wait_for_completion(&this_flusher.done);
2644 
2645         /*
2646          * Wake-up-and-cascade phase
2647          *
2648          * First flushers are responsible for cascading flushes and
2649          * handling overflow.  Non-first flushers can simply return.
2650          */
2651         if (wq->first_flusher != &this_flusher)
2652                 return;
2653 
2654         mutex_lock(&wq->mutex);
2655 
2656         /* we might have raced, check again with mutex held */
2657         if (wq->first_flusher != &this_flusher)
2658                 goto out_unlock;
2659 
2660         wq->first_flusher = NULL;
2661 
2662         WARN_ON_ONCE(!list_empty(&this_flusher.list));
2663         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2664 
2665         while (true) {
2666                 struct wq_flusher *next, *tmp;
2667 
2668                 /* complete all the flushers sharing the current flush color */
2669                 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2670                         if (next->flush_color != wq->flush_color)
2671                                 break;
2672                         list_del_init(&next->list);
2673                         complete(&next->done);
2674                 }
2675 
2676                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2677                              wq->flush_color != work_next_color(wq->work_color));
2678 
2679                 /* this flush_color is finished, advance by one */
2680                 wq->flush_color = work_next_color(wq->flush_color);
2681 
2682                 /* one color has been freed, handle overflow queue */
2683                 if (!list_empty(&wq->flusher_overflow)) {
2684                         /*
2685                          * Assign the same color to all overflowed
2686                          * flushers, advance work_color and append to
2687                          * flusher_queue.  This is the start-to-wait
2688                          * phase for these overflowed flushers.
2689                          */
2690                         list_for_each_entry(tmp, &wq->flusher_overflow, list)
2691                                 tmp->flush_color = wq->work_color;
2692 
2693                         wq->work_color = work_next_color(wq->work_color);
2694 
2695                         list_splice_tail_init(&wq->flusher_overflow,
2696                                               &wq->flusher_queue);
2697                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2698                 }
2699 
2700                 if (list_empty(&wq->flusher_queue)) {
2701                         WARN_ON_ONCE(wq->flush_color != wq->work_color);
2702                         break;
2703                 }
2704 
2705                 /*
2706                  * Need to flush more colors.  Make the next flusher
2707                  * the new first flusher and arm pwqs.
2708                  */
2709                 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2710                 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2711 
2712                 list_del_init(&next->list);
2713                 wq->first_flusher = next;
2714 
2715                 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2716                         break;
2717 
2718                 /*
2719                  * Meh... this color is already done, clear first
2720                  * flusher and repeat cascading.
2721                  */
2722                 wq->first_flusher = NULL;
2723         }
2724 
2725 out_unlock:
2726         mutex_unlock(&wq->mutex);
2727 }
2728 EXPORT_SYMBOL(flush_workqueue);
2729 
2730 /**
2731  * drain_workqueue - drain a workqueue
2732  * @wq: workqueue to drain
2733  *
2734  * Wait until the workqueue becomes empty.  While draining is in progress,
2735  * only chain queueing is allowed.  IOW, only currently pending or running
2736  * work items on @wq can queue further work items on it.  @wq is flushed
2737  * repeatedly until it becomes empty.  The number of flushing is determined
2738  * by the depth of chaining and should be relatively short.  Whine if it
2739  * takes too long.
2740  */
2741 void drain_workqueue(struct workqueue_struct *wq)
2742 {
2743         unsigned int flush_cnt = 0;
2744         struct pool_workqueue *pwq;
2745 
2746         /*
2747          * __queue_work() needs to test whether there are drainers, is much
2748          * hotter than drain_workqueue() and already looks at @wq->flags.
2749          * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2750          */
2751         mutex_lock(&wq->mutex);
2752         if (!wq->nr_drainers++)
2753                 wq->flags |= __WQ_DRAINING;
2754         mutex_unlock(&wq->mutex);
2755 reflush:
2756         flush_workqueue(wq);
2757 
2758         mutex_lock(&wq->mutex);
2759 
2760         for_each_pwq(pwq, wq) {
2761                 bool drained;
2762 
2763                 spin_lock_irq(&pwq->pool->lock);
2764                 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2765                 spin_unlock_irq(&pwq->pool->lock);
2766 
2767                 if (drained)
2768                         continue;
2769 
2770                 if (++flush_cnt == 10 ||
2771                     (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2772                         pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2773                                 wq->name, flush_cnt);
2774 
2775                 mutex_unlock(&wq->mutex);
2776                 goto reflush;
2777         }
2778 
2779         if (!--wq->nr_drainers)
2780                 wq->flags &= ~__WQ_DRAINING;
2781         mutex_unlock(&wq->mutex);
2782 }
2783 EXPORT_SYMBOL_GPL(drain_workqueue);
2784 
2785 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2786 {
2787         struct worker *worker = NULL;
2788         struct worker_pool *pool;
2789         struct pool_workqueue *pwq;
2790 
2791         might_sleep();
2792 
2793         local_irq_disable();
2794         pool = get_work_pool(work);
2795         if (!pool) {
2796                 local_irq_enable();
2797                 return false;
2798         }
2799 
2800         spin_lock(&pool->lock);
2801         /* see the comment in try_to_grab_pending() with the same code */
2802         pwq = get_work_pwq(work);
2803         if (pwq) {
2804                 if (unlikely(pwq->pool != pool))
2805                         goto already_gone;
2806         } else {
2807                 worker = find_worker_executing_work(pool, work);
2808                 if (!worker)
2809                         goto already_gone;
2810                 pwq = worker->current_pwq;
2811         }
2812 
2813         check_flush_dependency(pwq->wq, work);
2814 
2815         insert_wq_barrier(pwq, barr, work, worker);
2816         spin_unlock_irq(&pool->lock);
2817 
2818         /*
2819          * If @max_active is 1 or rescuer is in use, flushing another work
2820          * item on the same workqueue may lead to deadlock.  Make sure the
2821          * flusher is not running on the same workqueue by verifying write
2822          * access.
2823          */
2824         if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2825                 lock_map_acquire(&pwq->wq->lockdep_map);
2826         else
2827                 lock_map_acquire_read(&pwq->wq->lockdep_map);
2828         lock_map_release(&pwq->wq->lockdep_map);
2829 
2830         return true;
2831 already_gone:
2832         spin_unlock_irq(&pool->lock);
2833         return false;
2834 }
2835 
2836 /**
2837  * flush_work - wait for a work to finish executing the last queueing instance
2838  * @work: the work to flush
2839  *
2840  * Wait until @work has finished execution.  @work is guaranteed to be idle
2841  * on return if it hasn't been requeued since flush started.
2842  *
2843  * Return:
2844  * %true if flush_work() waited for the work to finish execution,
2845  * %false if it was already idle.
2846  */
2847 bool flush_work(struct work_struct *work)
2848 {
2849         struct wq_barrier barr;
2850 
2851         if (WARN_ON(!wq_online))
2852                 return false;
2853 
2854         lock_map_acquire(&work->lockdep_map);
2855         lock_map_release(&work->lockdep_map);
2856 
2857         if (start_flush_work(work, &barr)) {
2858                 wait_for_completion(&barr.done);
2859                 destroy_work_on_stack(&barr.work);
2860                 return true;
2861         } else {
2862                 return false;
2863         }
2864 }
2865 EXPORT_SYMBOL_GPL(flush_work);
2866 
2867 struct cwt_wait {
2868         wait_queue_t            wait;
2869         struct work_struct      *work;
2870 };
2871 
2872 static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
2873 {
2874         struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2875 
2876         if (cwait->work != key)
2877                 return 0;
2878         return autoremove_wake_function(wait, mode, sync, key);
2879 }
2880 
2881 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2882 {
2883         static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2884         unsigned long flags;
2885         int ret;
2886 
2887         do {
2888                 ret = try_to_grab_pending(work, is_dwork, &flags);
2889                 /*
2890                  * If someone else is already canceling, wait for it to
2891                  * finish.  flush_work() doesn't work for PREEMPT_NONE
2892                  * because we may get scheduled between @work's completion
2893                  * and the other canceling task resuming and clearing
2894                  * CANCELING - flush_work() will return false immediately
2895                  * as @work is no longer busy, try_to_grab_pending() will
2896                  * return -ENOENT as @work is still being canceled and the
2897                  * other canceling task won't be able to clear CANCELING as
2898                  * we're hogging the CPU.
2899                  *
2900                  * Let's wait for completion using a waitqueue.  As this
2901                  * may lead to the thundering herd problem, use a custom
2902                  * wake function which matches @work along with exclusive
2903                  * wait and wakeup.
2904                  */
2905                 if (unlikely(ret == -ENOENT)) {
2906                         struct cwt_wait cwait;
2907 
2908                         init_wait(&cwait.wait);
2909                         cwait.wait.func = cwt_wakefn;
2910                         cwait.work = work;
2911 
2912                         prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2913                                                   TASK_UNINTERRUPTIBLE);
2914                         if (work_is_canceling(work))
2915                                 schedule();
2916                         finish_wait(&cancel_waitq, &cwait.wait);
2917                 }
2918         } while (unlikely(ret < 0));
2919 
2920         /* tell other tasks trying to grab @work to back off */
2921         mark_work_canceling(work);
2922         local_irq_restore(flags);
2923 
2924         /*
2925          * This allows canceling during early boot.  We know that @work
2926          * isn't executing.
2927          */
2928         if (wq_online)
2929                 flush_work(work);
2930 
2931         clear_work_data(work);
2932 
2933         /*
2934          * Paired with prepare_to_wait() above so that either
2935          * waitqueue_active() is visible here or !work_is_canceling() is
2936          * visible there.
2937          */
2938         smp_mb();
2939         if (waitqueue_active(&cancel_waitq))
2940                 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2941 
2942         return ret;
2943 }
2944 
2945 /**
2946  * cancel_work_sync - cancel a work and wait for it to finish
2947  * @work: the work to cancel
2948  *
2949  * Cancel @work and wait for its execution to finish.  This function
2950  * can be used even if the work re-queues itself or migrates to
2951  * another workqueue.  On return from this function, @work is
2952  * guaranteed to be not pending or executing on any CPU.
2953  *
2954  * cancel_work_sync(&delayed_work->work) must not be used for
2955  * delayed_work's.  Use cancel_delayed_work_sync() instead.
2956  *
2957  * The caller must ensure that the workqueue on which @work was last
2958  * queued can't be destroyed before this function returns.
2959  *
2960  * Return:
2961  * %true if @work was pending, %false otherwise.
2962  */
2963 bool cancel_work_sync(struct work_struct *work)
2964 {
2965         return __cancel_work_timer(work, false);
2966 }
2967 EXPORT_SYMBOL_GPL(cancel_work_sync);
2968 
2969 /**
2970  * flush_delayed_work - wait for a dwork to finish executing the last queueing
2971  * @dwork: the delayed work to flush
2972  *
2973  * Delayed timer is cancelled and the pending work is queued for
2974  * immediate execution.  Like flush_work(), this function only
2975  * considers the last queueing instance of @dwork.
2976  *
2977  * Return:
2978  * %true if flush_work() waited for the work to finish execution,
2979  * %false if it was already idle.
2980  */
2981 bool flush_delayed_work(struct delayed_work *dwork)
2982 {
2983         local_irq_disable();
2984         if (del_timer_sync(&dwork->timer))
2985                 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2986         local_irq_enable();
2987         return flush_work(&dwork->work);
2988 }
2989 EXPORT_SYMBOL(flush_delayed_work);
2990 
2991 static bool __cancel_work(struct work_struct *work, bool is_dwork)
2992 {
2993         unsigned long flags;
2994         int ret;
2995 
2996         do {
2997                 ret = try_to_grab_pending(work, is_dwork, &flags);
2998         } while (unlikely(ret == -EAGAIN));
2999 
3000         if (unlikely(ret < 0))
3001                 return false;
3002 
3003         set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3004         local_irq_restore(flags);
3005         return ret;
3006 }
3007 
3008 /*
3009  * See cancel_delayed_work()
3010  */
3011 bool cancel_work(struct work_struct *work)
3012 {
3013         return __cancel_work(work, false);
3014 }
3015 
3016 /**
3017  * cancel_delayed_work - cancel a delayed work
3018  * @dwork: delayed_work to cancel
3019  *
3020  * Kill off a pending delayed_work.
3021  *
3022  * Return: %true if @dwork was pending and canceled; %false if it wasn't
3023  * pending.
3024  *
3025  * Note:
3026  * The work callback function may still be running on return, unless
3027  * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
3028  * use cancel_delayed_work_sync() to wait on it.
3029  *
3030  * This function is safe to call from any context including IRQ handler.
3031  */
3032 bool cancel_delayed_work(struct delayed_work *dwork)
3033 {
3034         return __cancel_work(&dwork->work, true);
3035 }
3036 EXPORT_SYMBOL(cancel_delayed_work);
3037 
3038 /**
3039  * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3040  * @dwork: the delayed work cancel
3041  *
3042  * This is cancel_work_sync() for delayed works.
3043  *
3044  * Return:
3045  * %true if @dwork was pending, %false otherwise.
3046  */
3047 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3048 {
3049         return __cancel_work_timer(&dwork->work, true);
3050 }
3051 EXPORT_SYMBOL(cancel_delayed_work_sync);
3052 
3053 /**
3054  * schedule_on_each_cpu - execute a function synchronously on each online CPU
3055  * @func: the function to call
3056  *
3057  * schedule_on_each_cpu() executes @func on each online CPU using the
3058  * system workqueue and blocks until all CPUs have completed.
3059  * schedule_on_each_cpu() is very slow.
3060  *
3061  * Return:
3062  * 0 on success, -errno on failure.
3063  */
3064 int schedule_on_each_cpu(work_func_t func)
3065 {
3066         int cpu;
3067         struct work_struct __percpu *works;
3068 
3069         works = alloc_percpu(struct work_struct);
3070         if (!works)
3071                 return -ENOMEM;
3072 
3073         get_online_cpus();
3074 
3075         for_each_online_cpu(cpu) {
3076                 struct work_struct *work = per_cpu_ptr(works, cpu);
3077 
3078                 INIT_WORK(work, func);
3079                 schedule_work_on(cpu, work);
3080         }
3081 
3082         for_each_online_cpu(cpu)
3083                 flush_work(per_cpu_ptr(works, cpu));
3084 
3085         put_online_cpus();
3086         free_percpu(works);
3087         return 0;
3088 }
3089 
3090 /**
3091  * execute_in_process_context - reliably execute the routine with user context
3092  * @fn:         the function to execute
3093  * @ew:         guaranteed storage for the execute work structure (must
3094  *              be available when the work executes)
3095  *
3096  * Executes the function immediately if process context is available,
3097  * otherwise schedules the function for delayed execution.
3098  *
3099  * Return:      0 - function was executed
3100  *              1 - function was scheduled for execution
3101  */
3102 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3103 {
3104         if (!in_interrupt()) {
3105                 fn(&ew->work);
3106                 return 0;
3107         }
3108 
3109         INIT_WORK(&ew->work, fn);
3110         schedule_work(&ew->work);
3111 
3112         return 1;
3113 }
3114 EXPORT_SYMBOL_GPL(execute_in_process_context);
3115 
3116 /**
3117  * free_workqueue_attrs - free a workqueue_attrs
3118  * @attrs: workqueue_attrs to free
3119  *
3120  * Undo alloc_workqueue_attrs().
3121  */
3122 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3123 {
3124         if (attrs) {
3125                 free_cpumask_var(attrs->cpumask);
3126                 kfree(attrs);
3127         }
3128 }
3129 
3130 /**
3131  * alloc_workqueue_attrs - allocate a workqueue_attrs
3132  * @gfp_mask: allocation mask to use
3133  *
3134  * Allocate a new workqueue_attrs, initialize with default settings and
3135  * return it.
3136  *
3137  * Return: The allocated new workqueue_attr on success. %NULL on failure.
3138  */
3139 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3140 {
3141         struct workqueue_attrs *attrs;
3142 
3143         attrs = kzalloc(sizeof(*attrs), gfp_mask);
3144         if (!attrs)
3145                 goto fail;
3146         if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3147                 goto fail;
3148 
3149         cpumask_copy(attrs->cpumask, cpu_possible_mask);
3150         return attrs;
3151 fail:
3152         free_workqueue_attrs(attrs);
3153         return NULL;
3154 }
3155 
3156 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3157                                  const struct workqueue_attrs *from)
3158 {
3159         to->nice = from->nice;
3160         cpumask_copy(to->cpumask, from->cpumask);
3161         /*
3162          * Unlike hash and equality test, this function doesn't ignore
3163          * ->no_numa as it is used for both pool and wq attrs.  Instead,
3164          * get_unbound_pool() explicitly clears ->no_numa after copying.
3165          */
3166         to->no_numa = from->no_numa;
3167 }
3168 
3169 /* hash value of the content of @attr */
3170 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3171 {
3172         u32 hash = 0;
3173 
3174         hash = jhash_1word(attrs->nice, hash);
3175         hash = jhash(cpumask_bits(attrs->cpumask),
3176                      BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3177         return hash;
3178 }
3179 
3180 /* content equality test */
3181 static bool wqattrs_equal(const struct workqueue_attrs *a,
3182                           const struct workqueue_attrs *b)
3183 {
3184         if (a->nice != b->nice)
3185                 return false;
3186         if (!cpumask_equal(a->cpumask, b->cpumask))
3187                 return false;
3188         return true;
3189 }
3190 
3191 /**
3192  * init_worker_pool - initialize a newly zalloc'd worker_pool
3193  * @pool: worker_pool to initialize
3194  *
3195  * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
3196  *
3197  * Return: 0 on success, -errno on failure.  Even on failure, all fields
3198  * inside @pool proper are initialized and put_unbound_pool() can be called
3199  * on @pool safely to release it.
3200  */
3201 static int init_worker_pool(struct worker_pool *pool)
3202 {
3203         spin_lock_init(&pool->lock);
3204         pool->id = -1;
3205         pool->cpu = -1;
3206         pool->node = NUMA_NO_NODE;
3207         pool->flags |= POOL_DISASSOCIATED;
3208         pool->watchdog_ts = jiffies;
3209         INIT_LIST_HEAD(&pool->worklist);
3210         INIT_LIST_HEAD(&pool->idle_list);
3211         hash_init(pool->busy_hash);
3212 
3213         init_timer_deferrable(&pool->idle_timer);
3214         pool->idle_timer.function = idle_worker_timeout;
3215         pool->idle_timer.data = (unsigned long)pool;
3216 
3217         setup_timer(&pool->mayday_timer, pool_mayday_timeout,
3218                     (unsigned long)pool);
3219 
3220         mutex_init(&pool->manager_arb);
3221         mutex_init(&pool->attach_mutex);
3222         INIT_LIST_HEAD(&pool->workers);
3223 
3224         ida_init(&pool->worker_ida);
3225         INIT_HLIST_NODE(&pool->hash_node);
3226         pool->refcnt = 1;
3227 
3228         /* shouldn't fail above this point */
3229         pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3230         if (!pool->attrs)
3231                 return -ENOMEM;
3232         return 0;
3233 }
3234 
3235 static void rcu_free_wq(struct rcu_head *rcu)
3236 {
3237         struct workqueue_struct *wq =
3238                 container_of(rcu, struct workqueue_struct, rcu);
3239 
3240         if (!(wq->flags & WQ_UNBOUND))
3241                 free_percpu(wq->cpu_pwqs);
3242         else
3243                 free_workqueue_attrs(wq->unbound_attrs);
3244 
3245         kfree(wq->rescuer);
3246         kfree(wq);
3247 }
3248 
3249 static void rcu_free_pool(struct rcu_head *rcu)
3250 {
3251         struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3252 
3253         ida_destroy(&pool->worker_ida);
3254         free_workqueue_attrs(pool->attrs);
3255         kfree(pool);
3256 }
3257 
3258 /**
3259  * put_unbound_pool - put a worker_pool
3260  * @pool: worker_pool to put
3261  *
3262  * Put @pool.  If its refcnt reaches zero, it gets destroyed in sched-RCU
3263  * safe manner.  get_unbound_pool() calls this function on its failure path
3264  * and this function should be able to release pools which went through,
3265  * successfully or not, init_worker_pool().
3266  *
3267  * Should be called with wq_pool_mutex held.
3268  */
3269 static void put_unbound_pool(struct worker_pool *pool)
3270 {
3271         DECLARE_COMPLETION_ONSTACK(detach_completion);
3272         struct worker *worker;
3273 
3274         lockdep_assert_held(&wq_pool_mutex);
3275 
3276         if (--pool->refcnt)
3277                 return;
3278 
3279         /* sanity checks */
3280         if (WARN_ON(!(pool->cpu < 0)) ||
3281             WARN_ON(!list_empty(&pool->worklist)))
3282                 return;
3283 
3284         /* release id and unhash */
3285         if (pool->id >= 0)
3286                 idr_remove(&worker_pool_idr, pool->id);
3287         hash_del(&pool->hash_node);
3288 
3289         /*
3290          * Become the manager and destroy all workers.  Grabbing
3291          * manager_arb prevents @pool's workers from blocking on
3292          * attach_mutex.
3293          */
3294         mutex_lock(&pool->manager_arb);
3295 
3296         spin_lock_irq(&pool->lock);
3297         while ((worker = first_idle_worker(pool)))
3298                 destroy_worker(worker);
3299         WARN_ON(pool->nr_workers || pool->nr_idle);
3300         spin_unlock_irq(&pool->lock);
3301 
3302         mutex_lock(&pool->attach_mutex);
3303         if (!list_empty(&pool->workers))
3304                 pool->detach_completion = &detach_completion;
3305         mutex_unlock(&pool->attach_mutex);
3306 
3307         if (pool->detach_completion)
3308                 wait_for_completion(pool->detach_completion);
3309 
3310         mutex_unlock(&pool->manager_arb);
3311 
3312         /* shut down the timers */
3313         del_timer_sync(&pool->idle_timer);
3314         del_timer_sync(&pool->mayday_timer);
3315 
3316         /* sched-RCU protected to allow dereferences from get_work_pool() */
3317         call_rcu_sched(&pool->rcu, rcu_free_pool);
3318 }
3319 
3320 /**
3321  * get_unbound_pool - get a worker_pool with the specified attributes
3322  * @attrs: the attributes of the worker_pool to get
3323  *
3324  * Obtain a worker_pool which has the same attributes as @attrs, bump the
3325  * reference count and return it.  If there already is a matching
3326  * worker_pool, it will be used; otherwise, this function attempts to
3327  * create a new one.
3328  *
3329  * Should be called with wq_pool_mutex held.
3330  *
3331  * Return: On success, a worker_pool with the same attributes as @attrs.
3332  * On failure, %NULL.
3333  */
3334 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3335 {
3336         u32 hash = wqattrs_hash(attrs);
3337         struct worker_pool *pool;
3338         int node;
3339         int target_node = NUMA_NO_NODE;
3340 
3341         lockdep_assert_held(&wq_pool_mutex);
3342 
3343         /* do we already have a matching pool? */
3344         hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3345                 if (wqattrs_equal(pool->attrs, attrs)) {
3346                         pool->refcnt++;
3347                         return pool;
3348                 }
3349         }
3350 
3351         /* if cpumask is contained inside a NUMA node, we belong to that node */
3352         if (wq_numa_enabled) {
3353                 for_each_node(node) {
3354                         if (cpumask_subset(attrs->cpumask,
3355                                            wq_numa_possible_cpumask[node])) {
3356                                 target_node = node;
3357                                 break;
3358                         }
3359                 }
3360         }
3361 
3362         /* nope, create a new one */
3363         pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3364         if (!pool || init_worker_pool(pool) < 0)
3365                 goto fail;
3366 
3367         lockdep_set_subclass(&pool->lock, 1);   /* see put_pwq() */
3368         copy_workqueue_attrs(pool->attrs, attrs);
3369         pool->node = target_node;
3370 
3371         /*
3372          * no_numa isn't a worker_pool attribute, always clear it.  See
3373          * 'struct workqueue_attrs' comments for detail.
3374          */
3375         pool->attrs->no_numa = false;
3376 
3377         if (worker_pool_assign_id(pool) < 0)
3378                 goto fail;
3379 
3380         /* create and start the initial worker */
3381         if (wq_online && !create_worker(pool))
3382                 goto fail;
3383 
3384         /* install */
3385         hash_add(unbound_pool_hash, &pool->hash_node, hash);
3386 
3387         return pool;
3388 fail:
3389         if (pool)
3390                 put_unbound_pool(pool);
3391         return NULL;
3392 }
3393 
3394 static void rcu_free_pwq(struct rcu_head *rcu)
3395 {
3396         kmem_cache_free(pwq_cache,
3397                         container_of(rcu, struct pool_workqueue, rcu));
3398 }
3399 
3400 /*
3401  * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3402  * and needs to be destroyed.
3403  */
3404 static void pwq_unbound_release_workfn(struct work_struct *work)
3405 {
3406         struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3407                                                   unbound_release_work);
3408         struct workqueue_struct *wq = pwq->wq;
3409         struct worker_pool *pool = pwq->pool;
3410         bool is_last;
3411 
3412         if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3413                 return;
3414 
3415         mutex_lock(&wq->mutex);
3416         list_del_rcu(&pwq->pwqs_node);
3417         is_last = list_empty(&wq->pwqs);
3418         mutex_unlock(&wq->mutex);
3419 
3420         mutex_lock(&wq_pool_mutex);
3421         put_unbound_pool(pool);
3422         mutex_unlock(&wq_pool_mutex);
3423 
3424         call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3425 
3426         /*
3427          * If we're the last pwq going away, @wq is already dead and no one
3428          * is gonna access it anymore.  Schedule RCU free.
3429          */
3430         if (is_last)
3431                 call_rcu_sched(&wq->rcu, rcu_free_wq);
3432 }
3433 
3434 /**
3435  * pwq_adjust_max_active - update a pwq's max_active to the current setting
3436  * @pwq: target pool_workqueue
3437  *
3438  * If @pwq isn't freezing, set @pwq->max_active to the associated
3439  * workqueue's saved_max_active and activate delayed work items
3440  * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
3441  */
3442 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3443 {
3444         struct workqueue_struct *wq = pwq->wq;
3445         bool freezable = wq->flags & WQ_FREEZABLE;
3446         unsigned long flags;
3447 
3448         /* for @wq->saved_max_active */
3449         lockdep_assert_held(&wq->mutex);
3450 
3451         /* fast exit for non-freezable wqs */
3452         if (!freezable && pwq->max_active == wq->saved_max_active)
3453                 return;
3454 
3455         /* this function can be called during early boot w/ irq disabled */
3456         spin_lock_irqsave(&pwq->pool->lock, flags);
3457 
3458         /*
3459          * During [un]freezing, the caller is responsible for ensuring that
3460          * this function is called at least once after @workqueue_freezing
3461          * is updated and visible.
3462          */
3463         if (!freezable || !workqueue_freezing) {
3464                 pwq->max_active = wq->saved_max_active;
3465 
3466                 while (!list_empty(&pwq->delayed_works) &&
3467                        pwq->nr_active < pwq->max_active)
3468                         pwq_activate_first_delayed(pwq);
3469 
3470                 /*
3471                  * Need to kick a worker after thawed or an unbound wq's
3472                  * max_active is bumped.  It's a slow path.  Do it always.
3473                  */
3474                 wake_up_worker(pwq->pool);
3475         } else {
3476                 pwq->max_active = 0;
3477         }
3478 
3479         spin_unlock_irqrestore(&pwq->pool->lock, flags);
3480 }
3481 
3482 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3483 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3484                      struct worker_pool *pool)
3485 {
3486         BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3487 
3488         memset(pwq, 0, sizeof(*pwq));
3489 
3490         pwq->pool = pool;
3491         pwq->wq = wq;
3492         pwq->flush_color = -1;
3493         pwq->refcnt = 1;
3494         INIT_LIST_HEAD(&pwq->delayed_works);
3495         INIT_LIST_HEAD(&pwq->pwqs_node);
3496         INIT_LIST_HEAD(&pwq->mayday_node);
3497         INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3498 }
3499 
3500 /* sync @pwq with the current state of its associated wq and link it */
3501 static void link_pwq(struct pool_workqueue *pwq)
3502 {
3503         struct workqueue_struct *wq = pwq->wq;
3504 
3505         lockdep_assert_held(&wq->mutex);
3506 
3507         /* may be called multiple times, ignore if already linked */
3508         if (!list_empty(&pwq->pwqs_node))
3509                 return;
3510 
3511         /* set the matching work_color */
3512         pwq->work_color = wq->work_color;
3513 
3514         /* sync max_active to the current setting */
3515         pwq_adjust_max_active(pwq);
3516 
3517         /* link in @pwq */
3518         list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3519 }
3520 
3521 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3522 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3523                                         const struct workqueue_attrs *attrs)
3524 {
3525         struct worker_pool *pool;
3526         struct pool_workqueue *pwq;
3527 
3528         lockdep_assert_held(&wq_pool_mutex);
3529 
3530         pool = get_unbound_pool(attrs);
3531         if (!pool)
3532                 return NULL;
3533 
3534         pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3535         if (!pwq) {
3536                 put_unbound_pool(pool);
3537                 return NULL;
3538         }
3539 
3540         init_pwq(pwq, wq, pool);
3541         return pwq;
3542 }
3543 
3544 /**
3545  * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3546  * @attrs: the wq_attrs of the default pwq of the target workqueue
3547  * @node: the target NUMA node
3548  * @cpu_going_down: if >= 0, the CPU to consider as offline
3549  * @cpumask: outarg, the resulting cpumask
3550  *
3551  * Calculate the cpumask a workqueue with @attrs should use on @node.  If
3552  * @cpu_going_down is >= 0, that cpu is considered offline during
3553  * calculation.  The result is stored in @cpumask.
3554  *
3555  * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
3556  * enabled and @node has online CPUs requested by @attrs, the returned
3557  * cpumask is the intersection of the possible CPUs of @node and
3558  * @attrs->cpumask.
3559  *
3560  * The caller is responsible for ensuring that the cpumask of @node stays
3561  * stable.
3562  *
3563  * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3564  * %false if equal.
3565  */
3566 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3567                                  int cpu_going_down, cpumask_t *cpumask)
3568 {
3569         if (!wq_numa_enabled || attrs->no_numa)
3570                 goto use_dfl;
3571 
3572         /* does @node have any online CPUs @attrs wants? */
3573         cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3574         if (cpu_going_down >= 0)
3575                 cpumask_clear_cpu(cpu_going_down, cpumask);
3576 
3577         if (cpumask_empty(cpumask))
3578                 goto use_dfl;
3579 
3580         /* yeap, return possible CPUs in @node that @attrs wants */
3581         cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3582         return !cpumask_equal(cpumask, attrs->cpumask);
3583 
3584 use_dfl:
3585         cpumask_copy(cpumask, attrs->cpumask);
3586         return false;
3587 }
3588 
3589 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3590 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3591                                                    int node,
3592                                                    struct pool_workqueue *pwq)
3593 {
3594         struct pool_workqueue *old_pwq;
3595 
3596         lockdep_assert_held(&wq_pool_mutex);
3597         lockdep_assert_held(&wq->mutex);
3598 
3599         /* link_pwq() can handle duplicate calls */
3600         link_pwq(pwq);
3601 
3602         old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3603         rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3604         return old_pwq;
3605 }
3606 
3607 /* context to store the prepared attrs & pwqs before applying */
3608 struct apply_wqattrs_ctx {
3609         struct workqueue_struct *wq;            /* target workqueue */
3610         struct workqueue_attrs  *attrs;         /* attrs to apply */
3611         struct list_head        list;           /* queued for batching commit */
3612         struct pool_workqueue   *dfl_pwq;
3613         struct pool_workqueue   *pwq_tbl[];
3614 };
3615 
3616 /* free the resources after success or abort */
3617 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3618 {
3619         if (ctx) {
3620                 int node;
3621 
3622                 for_each_node(node)
3623                         put_pwq_unlocked(ctx->pwq_tbl[node]);
3624                 put_pwq_unlocked(ctx->dfl_pwq);
3625 
3626                 free_workqueue_attrs(ctx->attrs);
3627 
3628                 kfree(ctx);
3629         }
3630 }
3631 
3632 /* allocate the attrs and pwqs for later installation */
3633 static struct apply_wqattrs_ctx *
3634 apply_wqattrs_prepare(struct workqueue_struct *wq,
3635                       const struct workqueue_attrs *attrs)
3636 {
3637         struct apply_wqattrs_ctx *ctx;
3638         struct workqueue_attrs *new_attrs, *tmp_attrs;
3639         int node;
3640 
3641         lockdep_assert_held(&wq_pool_mutex);
3642 
3643         ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3644                       GFP_KERNEL);
3645 
3646         new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3647         tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3648         if (!ctx || !new_attrs || !tmp_attrs)
3649                 goto out_free;
3650 
3651         /*
3652          * Calculate the attrs of the default pwq.
3653          * If the user configured cpumask doesn't overlap with the
3654          * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3655          */
3656         copy_workqueue_attrs(new_attrs, attrs);
3657         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3658         if (unlikely(cpumask_empty(new_attrs->cpumask)))
3659                 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3660 
3661         /*
3662          * We may create multiple pwqs with differing cpumasks.  Make a
3663          * copy of @new_attrs which will be modified and used to obtain
3664          * pools.
3665          */
3666         copy_workqueue_attrs(tmp_attrs, new_attrs);
3667 
3668         /*
3669          * If something goes wrong during CPU up/down, we'll fall back to
3670          * the default pwq covering whole @attrs->cpumask.  Always create
3671          * it even if we don't use it immediately.
3672          */
3673         ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3674         if (!ctx->dfl_pwq)
3675                 goto out_free;
3676 
3677         for_each_node(node) {
3678                 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3679                         ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3680                         if (!ctx->pwq_tbl[node])
3681                                 goto out_free;
3682                 } else {
3683                         ctx->dfl_pwq->refcnt++;
3684                         ctx->pwq_tbl[node] = ctx->dfl_pwq;
3685                 }
3686         }
3687 
3688         /* save the user configured attrs and sanitize it. */
3689         copy_workqueue_attrs(new_attrs, attrs);
3690         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3691         ctx->attrs = new_attrs;
3692 
3693         ctx->wq = wq;
3694         free_workqueue_attrs(tmp_attrs);
3695         return ctx;
3696 
3697 out_free:
3698         free_workqueue_attrs(tmp_attrs);
3699         free_workqueue_attrs(new_attrs);
3700         apply_wqattrs_cleanup(ctx);
3701         return NULL;
3702 }
3703 
3704 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3705 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3706 {
3707         int node;
3708 
3709         /* all pwqs have been created successfully, let's install'em */
3710         mutex_lock(&ctx->wq->mutex);
3711 
3712         copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3713 
3714         /* save the previous pwq and install the new one */
3715         for_each_node(node)
3716                 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3717                                                           ctx->pwq_tbl[node]);
3718 
3719         /* @dfl_pwq might not have been used, ensure it's linked */
3720         link_pwq(ctx->dfl_pwq);
3721         swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3722 
3723         mutex_unlock(&ctx->wq->mutex);
3724 }
3725 
3726 static void apply_wqattrs_lock(void)
3727 {
3728         /* CPUs should stay stable across pwq creations and installations */
3729         get_online_cpus();
3730         mutex_lock(&wq_pool_mutex);
3731 }
3732 
3733 static void apply_wqattrs_unlock(void)
3734 {
3735         mutex_unlock(&wq_pool_mutex);
3736         put_online_cpus();
3737 }
3738 
3739 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3740                                         const struct workqueue_attrs *attrs)
3741 {
3742         struct apply_wqattrs_ctx *ctx;
3743 
3744         /* only unbound workqueues can change attributes */
3745         if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3746                 return -EINVAL;
3747 
3748         /* creating multiple pwqs breaks ordering guarantee */
3749         if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3750                 return -EINVAL;
3751 
3752         ctx = apply_wqattrs_prepare(wq, attrs);
3753         if (!ctx)
3754                 return -ENOMEM;
3755 
3756         /* the ctx has been prepared successfully, let's commit it */
3757         apply_wqattrs_commit(ctx);
3758         apply_wqattrs_cleanup(ctx);
3759 
3760         return 0;
3761 }
3762 
3763 /**
3764  * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3765  * @wq: the target workqueue
3766  * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3767  *
3768  * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
3769  * machines, this function maps a separate pwq to each NUMA node with
3770  * possibles CPUs in @attrs->cpumask so that work items are affine to the
3771  * NUMA node it was issued on.  Older pwqs are released as in-flight work
3772  * items finish.  Note that a work item which repeatedly requeues itself
3773  * back-to-back will stay on its current pwq.
3774  *
3775  * Performs GFP_KERNEL allocations.
3776  *
3777  * Return: 0 on success and -errno on failure.
3778  */
3779 int apply_workqueue_attrs(struct workqueue_struct *wq,
3780                           const struct workqueue_attrs *attrs)
3781 {
3782         int ret;
3783 
3784         apply_wqattrs_lock();
3785         ret = apply_workqueue_attrs_locked(wq, attrs);
3786         apply_wqattrs_unlock();
3787 
3788         return ret;
3789 }
3790 
3791 /**
3792  * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3793  * @wq: the target workqueue
3794  * @cpu: the CPU coming up or going down
3795  * @online: whether @cpu is coming up or going down
3796  *
3797  * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3798  * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
3799  * @wq accordingly.
3800  *
3801  * If NUMA affinity can't be adjusted due to memory allocation failure, it
3802  * falls back to @wq->dfl_pwq which may not be optimal but is always
3803  * correct.
3804  *
3805  * Note that when the last allowed CPU of a NUMA node goes offline for a
3806  * workqueue with a cpumask spanning multiple nodes, the workers which were
3807  * already executing the work items for the workqueue will lose their CPU
3808  * affinity and may execute on any CPU.  This is similar to how per-cpu
3809  * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
3810  * affinity, it's the user's responsibility to flush the work item from
3811  * CPU_DOWN_PREPARE.
3812  */
3813 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3814                                    bool online)
3815 {
3816         int node = cpu_to_node(cpu);
3817         int cpu_off = online ? -1 : cpu;
3818         struct pool_workqueue *old_pwq = NULL, *pwq;
3819         struct workqueue_attrs *target_attrs;
3820         cpumask_t *cpumask;
3821 
3822         lockdep_assert_held(&wq_pool_mutex);
3823 
3824         if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3825             wq->unbound_attrs->no_numa)
3826                 return;
3827 
3828         /*
3829          * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3830          * Let's use a preallocated one.  The following buf is protected by
3831          * CPU hotplug exclusion.
3832          */
3833         target_attrs = wq_update_unbound_numa_attrs_buf;
3834         cpumask = target_attrs->cpumask;
3835 
3836         copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3837         pwq = unbound_pwq_by_node(wq, node);
3838 
3839         /*
3840          * Let's determine what needs to be done.  If the target cpumask is
3841          * different from the default pwq's, we need to compare it to @pwq's
3842          * and create a new one if they don't match.  If the target cpumask
3843          * equals the default pwq's, the default pwq should be used.
3844          */
3845         if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3846                 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3847                         return;
3848         } else {
3849                 goto use_dfl_pwq;
3850         }
3851 
3852         /* create a new pwq */
3853         pwq = alloc_unbound_pwq(wq, target_attrs);
3854         if (!pwq) {
3855                 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3856                         wq->name);
3857                 goto use_dfl_pwq;
3858         }
3859 
3860         /* Install the new pwq. */
3861         mutex_lock(&wq->mutex);
3862         old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3863         goto out_unlock;
3864 
3865 use_dfl_pwq:
3866         mutex_lock(&wq->mutex);
3867         spin_lock_irq(&wq->dfl_pwq->pool->lock);
3868         get_pwq(wq->dfl_pwq);
3869         spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3870         old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3871 out_unlock:
3872         mutex_unlock(&wq->mutex);
3873         put_pwq_unlocked(old_pwq);
3874 }
3875 
3876 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3877 {
3878         bool highpri = wq->flags & WQ_HIGHPRI;
3879         int cpu, ret;
3880 
3881         if (!(wq->flags & WQ_UNBOUND)) {
3882                 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3883                 if (!wq->cpu_pwqs)
3884                         return -ENOMEM;
3885 
3886                 for_each_possible_cpu(cpu) {
3887                         struct pool_workqueue *pwq =
3888                                 per_cpu_ptr(wq->cpu_pwqs, cpu);
3889                         struct worker_pool *cpu_pools =
3890                                 per_cpu(cpu_worker_pools, cpu);
3891 
3892                         init_pwq(pwq, wq, &cpu_pools[highpri]);
3893 
3894                         mutex_lock(&wq->mutex);
3895                         link_pwq(pwq);
3896                         mutex_unlock(&wq->mutex);
3897                 }
3898                 return 0;
3899         } else if (wq->flags & __WQ_ORDERED) {
3900                 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3901                 /* there should only be single pwq for ordering guarantee */
3902                 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3903                               wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3904                      "ordering guarantee broken for workqueue %s\n", wq->name);
3905                 return ret;
3906         } else {
3907                 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3908         }
3909 }
3910 
3911 static int wq_clamp_max_active(int max_active, unsigned int flags,
3912                                const char *name)
3913 {
3914         int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3915 
3916         if (max_active < 1 || max_active > lim)
3917                 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3918                         max_active, name, 1, lim);
3919 
3920         return clamp_val(max_active, 1, lim);
3921 }
3922 
3923 struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3924                                                unsigned int flags,
3925                                                int max_active,
3926                                                struct lock_class_key *key,
3927                                                const char *lock_name, ...)
3928 {
3929         size_t tbl_size = 0;
3930         va_list args;
3931         struct workqueue_struct *wq;
3932         struct pool_workqueue *pwq;
3933 
3934         /* see the comment above the definition of WQ_POWER_EFFICIENT */
3935         if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3936                 flags |= WQ_UNBOUND;
3937 
3938         /* allocate wq and format name */
3939         if (flags & WQ_UNBOUND)
3940                 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
3941 
3942         wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
3943         if (!wq)
3944                 return NULL;
3945 
3946         if (flags & WQ_UNBOUND) {
3947                 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3948                 if (!wq->unbound_attrs)
3949                         goto err_free_wq;
3950         }
3951 
3952         va_start(args, lock_name);
3953         vsnprintf(wq->name, sizeof(wq->name), fmt, args);
3954         va_end(args);
3955 
3956         max_active = max_active ?: WQ_DFL_ACTIVE;
3957         max_active = wq_clamp_max_active(max_active, flags, wq->name);
3958 
3959         /* init wq */
3960         wq->flags = flags;
3961         wq->saved_max_active = max_active;
3962         mutex_init(&wq->mutex);
3963         atomic_set(&wq->nr_pwqs_to_flush, 0);
3964         INIT_LIST_HEAD(&wq->pwqs);
3965         INIT_LIST_HEAD(&wq->flusher_queue);
3966         INIT_LIST_HEAD(&wq->flusher_overflow);
3967         INIT_LIST_HEAD(&wq->maydays);
3968 
3969         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3970         INIT_LIST_HEAD(&wq->list);
3971 
3972         if (alloc_and_link_pwqs(wq) < 0)
3973                 goto err_free_wq;
3974 
3975         /*
3976          * Workqueues which may be used during memory reclaim should
3977          * have a rescuer to guarantee forward progress.
3978          */
3979         if (flags & WQ_MEM_RECLAIM) {
3980                 struct worker *rescuer;
3981 
3982                 rescuer = alloc_worker(NUMA_NO_NODE);
3983                 if (!rescuer)
3984                         goto err_destroy;
3985 
3986                 rescuer->rescue_wq = wq;
3987                 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
3988                                                wq->name);
3989                 if (IS_ERR(rescuer->task)) {
3990                         kfree(rescuer);
3991                         goto err_destroy;
3992                 }
3993 
3994                 wq->rescuer = rescuer;
3995                 kthread_bind_mask(rescuer->task, cpu_possible_mask);
3996                 wake_up_process(rescuer->task);
3997         }
3998 
3999         if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4000                 goto err_destroy;
4001 
4002         /*
4003          * wq_pool_mutex protects global freeze state and workqueues list.
4004          * Grab it, adjust max_active and add the new @wq to workqueues
4005          * list.
4006          */
4007         mutex_lock(&wq_pool_mutex);
4008 
4009         mutex_lock(&wq->mutex);
4010         for_each_pwq(pwq, wq)
4011                 pwq_adjust_max_active(pwq);
4012         mutex_unlock(&wq->mutex);
4013 
4014         list_add_tail_rcu(&wq->list, &workqueues);
4015 
4016         mutex_unlock(&wq_pool_mutex);
4017 
4018         return wq;
4019 
4020 err_free_wq:
4021         free_workqueue_attrs(wq->unbound_attrs);
4022         kfree(wq);
4023         return NULL;
4024 err_destroy:
4025         destroy_workqueue(wq);
4026         return NULL;
4027 }
4028 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4029 
4030 /**
4031  * destroy_workqueue - safely terminate a workqueue
4032  * @wq: target workqueue
4033  *
4034  * Safely destroy a workqueue. All work currently pending will be done first.
4035  */
4036 void destroy_workqueue(struct workqueue_struct *wq)
4037 {
4038         struct pool_workqueue *pwq;
4039         int node;
4040 
4041         /* drain it before proceeding with destruction */
4042         drain_workqueue(wq);
4043 
4044         /* sanity checks */
4045         mutex_lock(&wq->mutex);
4046         for_each_pwq(pwq, wq) {
4047                 int i;
4048 
4049                 for (i = 0; i < WORK_NR_COLORS; i++) {
4050                         if (WARN_ON(pwq->nr_in_flight[i])) {
4051                                 mutex_unlock(&wq->mutex);
4052                                 show_workqueue_state();
4053                                 return;
4054                         }
4055                 }
4056 
4057                 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4058                     WARN_ON(pwq->nr_active) ||
4059                     WARN_ON(!list_empty(&pwq->delayed_works))) {
4060                         mutex_unlock(&wq->mutex);
4061                         show_workqueue_state();
4062                         return;
4063                 }
4064         }
4065         mutex_unlock(&wq->mutex);
4066 
4067         /*
4068          * wq list is used to freeze wq, remove from list after
4069          * flushing is complete in case freeze races us.
4070          */
4071         mutex_lock(&wq_pool_mutex);
4072         list_del_rcu(&wq->list);
4073         mutex_unlock(&wq_pool_mutex);
4074 
4075         workqueue_sysfs_unregister(wq);
4076 
4077         if (wq->rescuer)
4078                 kthread_stop(wq->rescuer->task);
4079 
4080         if (!(wq->flags & WQ_UNBOUND)) {
4081                 /*
4082                  * The base ref is never dropped on per-cpu pwqs.  Directly
4083                  * schedule RCU free.
4084                  */
4085                 call_rcu_sched(&wq->rcu, rcu_free_wq);
4086         } else {
4087                 /*
4088                  * We're the sole accessor of @wq at this point.  Directly
4089                  * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4090                  * @wq will be freed when the last pwq is released.
4091                  */
4092                 for_each_node(node) {
4093                         pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4094                         RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4095                         put_pwq_unlocked(pwq);
4096                 }
4097 
4098                 /*
4099                  * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
4100                  * put.  Don't access it afterwards.
4101                  */
4102                 pwq = wq->dfl_pwq;
4103                 wq->dfl_pwq = NULL;
4104                 put_pwq_unlocked(pwq);
4105         }
4106 }
4107 EXPORT_SYMBOL_GPL(destroy_workqueue);
4108 
4109 /**
4110  * workqueue_set_max_active - adjust max_active of a workqueue
4111  * @wq: target workqueue
4112  * @max_active: new max_active value.
4113  *
4114  * Set max_active of @wq to @max_active.
4115  *
4116  * CONTEXT:
4117  * Don't call from IRQ context.
4118  */
4119 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4120 {
4121         struct pool_workqueue *pwq;
4122 
4123         /* disallow meddling with max_active for ordered workqueues */
4124         if (WARN_ON(wq->flags & __WQ_ORDERED))
4125                 return;
4126 
4127         max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4128 
4129         mutex_lock(&wq->mutex);
4130 
4131         wq->saved_max_active = max_active;
4132 
4133         for_each_pwq(pwq, wq)
4134                 pwq_adjust_max_active(pwq);
4135 
4136         mutex_unlock(&wq->mutex);
4137 }
4138 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4139 
4140 /**
4141  * current_is_workqueue_rescuer - is %current workqueue rescuer?
4142  *
4143  * Determine whether %current is a workqueue rescuer.  Can be used from
4144  * work functions to determine whether it's being run off the rescuer task.
4145  *
4146  * Return: %true if %current is a workqueue rescuer. %false otherwise.
4147  */
4148 bool current_is_workqueue_rescuer(void)
4149 {
4150         struct worker *worker = current_wq_worker();
4151 
4152         return worker && worker->rescue_wq;
4153 }
4154 
4155 /**
4156  * workqueue_congested - test whether a workqueue is congested
4157  * @cpu: CPU in question
4158  * @wq: target workqueue
4159  *
4160  * Test whether @wq's cpu workqueue for @cpu is congested.  There is
4161  * no synchronization around this function and the test result is
4162  * unreliable and only useful as advisory hints or for debugging.
4163  *
4164  * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4165  * Note that both per-cpu and unbound workqueues may be associated with
4166  * multiple pool_workqueues which have separate congested states.  A
4167  * workqueue being congested on one CPU doesn't mean the workqueue is also
4168  * contested on other CPUs / NUMA nodes.
4169  *
4170  * Return:
4171  * %true if congested, %false otherwise.
4172  */
4173 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4174 {
4175         struct pool_workqueue *pwq;
4176         bool ret;
4177 
4178         rcu_read_lock_sched();
4179 
4180         if (cpu == WORK_CPU_UNBOUND)
4181                 cpu = smp_processor_id();
4182 
4183         if (!(wq->flags & WQ_UNBOUND))
4184                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4185         else
4186                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4187 
4188         ret = !list_empty(&pwq->delayed_works);
4189         rcu_read_unlock_sched();
4190 
4191         return ret;
4192 }
4193 EXPORT_SYMBOL_GPL(workqueue_congested);
4194 
4195 /**
4196  * work_busy - test whether a work is currently pending or running
4197  * @work: the work to be tested
4198  *
4199  * Test whether @work is currently pending or running.  There is no
4200  * synchronization around this function and the test result is
4201  * unreliable and only useful as advisory hints or for debugging.
4202  *
4203  * Return:
4204  * OR'd bitmask of WORK_BUSY_* bits.
4205  */
4206 unsigned int work_busy(struct work_struct *work)
4207 {
4208         struct worker_pool *pool;
4209         unsigned long flags;
4210         unsigned int ret = 0;
4211 
4212         if (work_pending(work))
4213                 ret |= WORK_BUSY_PENDING;
4214 
4215         local_irq_save(flags);
4216         pool = get_work_pool(work);
4217         if (pool) {
4218                 spin_lock(&pool->lock);
4219                 if (find_worker_executing_work(pool, work))
4220                         ret |= WORK_BUSY_RUNNING;
4221                 spin_unlock(&pool->lock);
4222         }
4223         local_irq_restore(flags);
4224 
4225         return ret;
4226 }
4227 EXPORT_SYMBOL_GPL(work_busy);
4228 
4229 /**
4230  * set_worker_desc - set description for the current work item
4231  * @fmt: printf-style format string
4232  * @...: arguments for the format string
4233  *
4234  * This function can be called by a running work function to describe what
4235  * the work item is about.  If the worker task gets dumped, this
4236  * information will be printed out together to help debugging.  The
4237  * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4238  */
4239 void set_worker_desc(const char *fmt, ...)
4240 {
4241         struct worker *worker = current_wq_worker();
4242         va_list args;
4243 
4244         if (worker) {
4245                 va_start(args, fmt);
4246                 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4247                 va_end(args);
4248                 worker->desc_valid = true;
4249         }
4250 }
4251 
4252 /**
4253  * print_worker_info - print out worker information and description
4254  * @log_lvl: the log level to use when printing
4255  * @task: target task
4256  *
4257  * If @task is a worker and currently executing a work item, print out the
4258  * name of the workqueue being serviced and worker description set with
4259  * set_worker_desc() by the currently executing work item.
4260  *
4261  * This function can be safely called on any task as long as the
4262  * task_struct itself is accessible.  While safe, this function isn't
4263  * synchronized and may print out mixups or garbages of limited length.
4264  */
4265 void print_worker_info(const char *log_lvl, struct task_struct *task)
4266 {
4267         work_func_t *fn = NULL;
4268         char name[WQ_NAME_LEN] = { };
4269         char desc[WORKER_DESC_LEN] = { };
4270         struct pool_workqueue *pwq = NULL;
4271         struct workqueue_struct *wq = NULL;
4272         bool desc_valid = false;
4273         struct worker *worker;
4274 
4275         if (!(task->flags & PF_WQ_WORKER))
4276                 return;
4277 
4278         /*
4279          * This function is called without any synchronization and @task
4280          * could be in any state.  Be careful with dereferences.
4281          */
4282         worker = kthread_probe_data(task);
4283 
4284         /*
4285          * Carefully copy the associated workqueue's workfn and name.  Keep
4286          * the original last '\0' in case the original contains garbage.
4287          */
4288         probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4289         probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4290         probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4291         probe_kernel_read(name, wq->name, sizeof(name) - 1);
4292 
4293         /* copy worker description */
4294         probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4295         if (desc_valid)
4296                 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4297 
4298         if (fn || name[0] || desc[0]) {
4299                 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4300                 if (desc[0])
4301                         pr_cont(" (%s)", desc);
4302                 pr_cont("\n");
4303         }
4304 }
4305 
4306 static void pr_cont_pool_info(struct worker_pool *pool)
4307 {
4308         pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4309         if (pool->node != NUMA_NO_NODE)
4310                 pr_cont(" node=%d", pool->node);
4311         pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4312 }
4313 
4314 static void pr_cont_work(bool comma, struct work_struct *work)
4315 {
4316         if (work->func == wq_barrier_func) {
4317                 struct wq_barrier *barr;
4318 
4319                 barr = container_of(work, struct wq_barrier, work);
4320 
4321                 pr_cont("%s BAR(%d)", comma ? "," : "",
4322                         task_pid_nr(barr->task));
4323         } else {
4324                 pr_cont("%s %pf", comma ? "," : "", work->func);
4325         }
4326 }
4327 
4328 static void show_pwq(struct pool_workqueue *pwq)
4329 {
4330         struct worker_pool *pool = pwq->pool;
4331         struct work_struct *work;
4332         struct worker *worker;
4333         bool has_in_flight = false, has_pending = false;
4334         int bkt;
4335 
4336         pr_info("  pwq %d:", pool->id);
4337         pr_cont_pool_info(pool);
4338 
4339         pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4340                 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4341 
4342         hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4343                 if (worker->current_pwq == pwq) {
4344                         has_in_flight = true;
4345                         break;
4346                 }
4347         }
4348         if (has_in_flight) {
4349                 bool comma = false;
4350 
4351                 pr_info("    in-flight:");
4352                 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4353                         if (worker->current_pwq != pwq)
4354                                 continue;
4355 
4356                         pr_cont("%s %d%s:%pf", comma ? "," : "",
4357                                 task_pid_nr(worker->task),
4358                                 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4359                                 worker->current_func);
4360                         list_for_each_entry(work, &worker->scheduled, entry)
4361                                 pr_cont_work(false, work);
4362                         comma = true;
4363                 }
4364                 pr_cont("\n");
4365         }
4366 
4367         list_for_each_entry(work, &pool->worklist, entry) {
4368                 if (get_work_pwq(work) == pwq) {
4369                         has_pending = true;
4370                         break;
4371                 }
4372         }
4373         if (has_pending) {
4374                 bool comma = false;
4375 
4376                 pr_info("    pending:");
4377                 list_for_each_entry(work, &pool->worklist, entry) {
4378                         if (get_work_pwq(work) != pwq)
4379                                 continue;
4380 
4381                         pr_cont_work(comma, work);
4382                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4383                 }
4384                 pr_cont("\n");
4385         }
4386 
4387         if (!list_empty(&pwq->delayed_works)) {
4388                 bool comma = false;
4389 
4390                 pr_info("    delayed:");
4391                 list_for_each_entry(work, &pwq->delayed_works, entry) {
4392                         pr_cont_work(comma, work);
4393                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4394                 }
4395                 pr_cont("\n");
4396         }
4397 }
4398 
4399 /**
4400  * show_workqueue_state - dump workqueue state
4401  *
4402  * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4403  * all busy workqueues and pools.
4404  */
4405 void show_workqueue_state(void)
4406 {
4407         struct workqueue_struct *wq;
4408         struct worker_pool *pool;
4409         unsigned long flags;
4410         int pi;
4411 
4412         rcu_read_lock_sched();
4413 
4414         pr_info("Showing busy workqueues and worker pools:\n");
4415 
4416         list_for_each_entry_rcu(wq, &workqueues, list) {
4417                 struct pool_workqueue *pwq;
4418                 bool idle = true;
4419 
4420                 for_each_pwq(pwq, wq) {
4421                         if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4422                                 idle = false;
4423                                 break;
4424                         }
4425                 }
4426                 if (idle)
4427                         continue;
4428 
4429                 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4430 
4431                 for_each_pwq(pwq, wq) {
4432                         spin_lock_irqsave(&pwq->pool->lock, flags);
4433                         if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4434                                 show_pwq(pwq);
4435                         spin_unlock_irqrestore(&pwq->pool->lock, flags);
4436                 }
4437         }
4438 
4439         for_each_pool(pool, pi) {
4440                 struct worker *worker;
4441                 bool first = true;
4442 
4443                 spin_lock_irqsave(&pool->lock, flags);
4444                 if (pool->nr_workers == pool->nr_idle)
4445                         goto next_pool;
4446 
4447                 pr_info("pool %d:", pool->id);
4448                 pr_cont_pool_info(pool);
4449                 pr_cont(" hung=%us workers=%d",
4450                         jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4451                         pool->nr_workers);
4452                 if (pool->manager)
4453                         pr_cont(" manager: %d",
4454                                 task_pid_nr(pool->manager->task));
4455                 list_for_each_entry(worker, &pool->idle_list, entry) {
4456                         pr_cont(" %s%d", first ? "idle: " : "",
4457                                 task_pid_nr(worker->task));
4458                         first = false;
4459                 }
4460                 pr_cont("\n");
4461         next_pool:
4462                 spin_unlock_irqrestore(&pool->lock, flags);
4463         }
4464 
4465         rcu_read_unlock_sched();
4466 }
4467 
4468 /*
4469  * CPU hotplug.
4470  *
4471  * There are two challenges in supporting CPU hotplug.  Firstly, there
4472  * are a lot of assumptions on strong associations among work, pwq and
4473  * pool which make migrating pending and scheduled works very
4474  * difficult to implement without impacting hot paths.  Secondly,
4475  * worker pools serve mix of short, long and very long running works making
4476  * blocked draining impractical.
4477  *
4478  * This is solved by allowing the pools to be disassociated from the CPU
4479  * running as an unbound one and allowing it to be reattached later if the
4480  * cpu comes back online.
4481  */
4482 
4483 static void wq_unbind_fn(struct work_struct *work)
4484 {
4485         int cpu = smp_processor_id();
4486         struct worker_pool *pool;
4487         struct worker *worker;
4488 
4489         for_each_cpu_worker_pool(pool, cpu) {
4490                 mutex_lock(&pool->attach_mutex);
4491                 spin_lock_irq(&pool->lock);
4492 
4493                 /*
4494                  * We've blocked all attach/detach operations. Make all workers
4495                  * unbound and set DISASSOCIATED.  Before this, all workers
4496                  * except for the ones which are still executing works from
4497                  * before the last CPU down must be on the cpu.  After
4498                  * this, they may become diasporas.
4499                  */
4500                 for_each_pool_worker(worker, pool)
4501                         worker->flags |= WORKER_UNBOUND;
4502 
4503                 pool->flags |= POOL_DISASSOCIATED;
4504 
4505                 spin_unlock_irq(&pool->lock);
4506                 mutex_unlock(&pool->attach_mutex);
4507 
4508                 /*
4509                  * Call schedule() so that we cross rq->lock and thus can
4510                  * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4511                  * This is necessary as scheduler callbacks may be invoked
4512                  * from other cpus.
4513                  */
4514                 schedule();
4515 
4516                 /*
4517                  * Sched callbacks are disabled now.  Zap nr_running.
4518                  * After this, nr_running stays zero and need_more_worker()
4519                  * and keep_working() are always true as long as the
4520                  * worklist is not empty.  This pool now behaves as an
4521                  * unbound (in terms of concurrency management) pool which
4522                  * are served by workers tied to the pool.
4523                  */
4524                 atomic_set(&pool->nr_running, 0);
4525 
4526                 /*
4527                  * With concurrency management just turned off, a busy
4528                  * worker blocking could lead to lengthy stalls.  Kick off
4529                  * unbound chain execution of currently pending work items.
4530                  */
4531                 spin_lock_irq(&pool->lock);
4532                 wake_up_worker(pool);
4533                 spin_unlock_irq(&pool->lock);
4534         }
4535 }
4536 
4537 /**
4538  * rebind_workers - rebind all workers of a pool to the associated CPU
4539  * @pool: pool of interest
4540  *
4541  * @pool->cpu is coming online.  Rebind all workers to the CPU.
4542  */
4543 static void rebind_workers(struct worker_pool *pool)
4544 {
4545         struct worker *worker;
4546 
4547         lockdep_assert_held(&pool->attach_mutex);
4548 
4549         /*
4550          * Restore CPU affinity of all workers.  As all idle workers should
4551          * be on the run-queue of the associated CPU before any local
4552          * wake-ups for concurrency management happen, restore CPU affinity
4553          * of all workers first and then clear UNBOUND.  As we're called
4554          * from CPU_ONLINE, the following shouldn't fail.
4555          */
4556         for_each_pool_worker(worker, pool)
4557                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4558                                                   pool->attrs->cpumask) < 0);
4559 
4560         spin_lock_irq(&pool->lock);
4561 
4562         /*
4563          * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
4564          * w/o preceding DOWN_PREPARE.  Work around it.  CPU hotplug is
4565          * being reworked and this can go away in time.
4566          */
4567         if (!(pool->flags & POOL_DISASSOCIATED)) {
4568                 spin_unlock_irq(&pool->lock);
4569                 return;
4570         }
4571 
4572         pool->flags &= ~POOL_DISASSOCIATED;
4573 
4574         for_each_pool_worker(worker, pool) {
4575                 unsigned int worker_flags = worker->flags;
4576 
4577                 /*
4578                  * A bound idle worker should actually be on the runqueue
4579                  * of the associated CPU for local wake-ups targeting it to
4580                  * work.  Kick all idle workers so that they migrate to the
4581                  * associated CPU.  Doing this in the same loop as
4582                  * replacing UNBOUND with REBOUND is safe as no worker will
4583                  * be bound before @pool->lock is released.
4584                  */
4585                 if (worker_flags & WORKER_IDLE)
4586                         wake_up_process(worker->task);
4587 
4588                 /*
4589                  * We want to clear UNBOUND but can't directly call
4590                  * worker_clr_flags() or adjust nr_running.  Atomically
4591                  * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4592                  * @worker will clear REBOUND using worker_clr_flags() when
4593                  * it initiates the next execution cycle thus restoring
4594                  * concurrency management.  Note that when or whether
4595                  * @worker clears REBOUND doesn't affect correctness.
4596                  *
4597                  * ACCESS_ONCE() is necessary because @worker->flags may be
4598                  * tested without holding any lock in
4599                  * wq_worker_waking_up().  Without it, NOT_RUNNING test may
4600                  * fail incorrectly leading to premature concurrency
4601                  * management operations.
4602                  */
4603                 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4604                 worker_flags |= WORKER_REBOUND;
4605                 worker_flags &= ~WORKER_UNBOUND;
4606                 ACCESS_ONCE(worker->flags) = worker_flags;
4607         }
4608 
4609         spin_unlock_irq(&pool->lock);
4610 }
4611 
4612 /**
4613  * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4614  * @pool: unbound pool of interest
4615  * @cpu: the CPU which is coming up
4616  *
4617  * An unbound pool may end up with a cpumask which doesn't have any online
4618  * CPUs.  When a worker of such pool get scheduled, the scheduler resets
4619  * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
4620  * online CPU before, cpus_allowed of all its workers should be restored.
4621  */
4622 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4623 {
4624         static cpumask_t cpumask;
4625         struct worker *worker;
4626 
4627         lockdep_assert_held(&pool->attach_mutex);
4628 
4629         /* is @cpu allowed for @pool? */
4630         if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4631                 return;
4632 
4633         cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4634 
4635         /* as we're called from CPU_ONLINE, the following shouldn't fail */
4636         for_each_pool_worker(worker, pool)
4637                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4638 }
4639 
4640 int workqueue_prepare_cpu(unsigned int cpu)
4641 {
4642         struct worker_pool *pool;
4643 
4644         for_each_cpu_worker_pool(pool, cpu) {
4645                 if (pool->nr_workers)
4646                         continue;
4647                 if (!create_worker(pool))
4648                         return -ENOMEM;
4649         }
4650         return 0;
4651 }
4652 
4653 int workqueue_online_cpu(unsigned int cpu)
4654 {
4655         struct worker_pool *pool;
4656         struct workqueue_struct *wq;
4657         int pi;
4658 
4659         mutex_lock(&wq_pool_mutex);
4660 
4661         for_each_pool(pool, pi) {
4662                 mutex_lock(&pool->attach_mutex);
4663 
4664                 if (pool->cpu == cpu)
4665                         rebind_workers(pool);
4666                 else if (pool->cpu < 0)
4667                         restore_unbound_workers_cpumask(pool, cpu);
4668 
4669                 mutex_unlock(&pool->attach_mutex);
4670         }
4671 
4672         /* update NUMA affinity of unbound workqueues */
4673         list_for_each_entry(wq, &workqueues, list)
4674                 wq_update_unbound_numa(wq, cpu, true);
4675 
4676         mutex_unlock(&wq_pool_mutex);
4677         return 0;
4678 }
4679 
4680 int workqueue_offline_cpu(unsigned int cpu)
4681 {
4682         struct work_struct unbind_work;
4683         struct workqueue_struct *wq;
4684 
4685         /* unbinding per-cpu workers should happen on the local CPU */
4686         INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4687         queue_work_on(cpu, system_highpri_wq, &unbind_work);
4688 
4689         /* update NUMA affinity of unbound workqueues */
4690         mutex_lock(&wq_pool_mutex);
4691         list_for_each_entry(wq, &workqueues, list)
4692                 wq_update_unbound_numa(wq, cpu, false);
4693         mutex_unlock(&wq_pool_mutex);
4694 
4695         /* wait for per-cpu unbinding to finish */
4696         flush_work(&unbind_work);
4697         destroy_work_on_stack(&unbind_work);
4698         return 0;
4699 }
4700 
4701 #ifdef CONFIG_SMP
4702 
4703 struct work_for_cpu {
4704         struct work_struct work;
4705         long (*fn)(void *);
4706         void *arg;
4707         long ret;
4708 };
4709 
4710 static void work_for_cpu_fn(struct work_struct *work)
4711 {
4712         struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4713 
4714         wfc->ret = wfc->fn(wfc->arg);
4715 }
4716 
4717 /**
4718  * work_on_cpu - run a function in thread context on a particular cpu
4719  * @cpu: the cpu to run on
4720  * @fn: the function to run
4721  * @arg: the function arg
4722  *
4723  * It is up to the caller to ensure that the cpu doesn't go offline.
4724  * The caller must not hold any locks which would prevent @fn from completing.
4725  *
4726  * Return: The value @fn returns.
4727  */
4728 long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4729 {
4730         struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4731 
4732         INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4733         schedule_work_on(cpu, &wfc.work);
4734         flush_work(&wfc.work);
4735         destroy_work_on_stack(&wfc.work);
4736         return wfc.ret;
4737 }
4738 EXPORT_SYMBOL_GPL(work_on_cpu);
4739 #endif /* CONFIG_SMP */
4740 
4741 #ifdef CONFIG_FREEZER
4742 
4743 /**
4744  * freeze_workqueues_begin - begin freezing workqueues
4745  *
4746  * Start freezing workqueues.  After this function returns, all freezable
4747  * workqueues will queue new works to their delayed_works list instead of
4748  * pool->worklist.
4749  *
4750  * CONTEXT:
4751  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4752  */
4753 void freeze_workqueues_begin(void)
4754 {
4755         struct workqueue_struct *wq;
4756         struct pool_workqueue *pwq;
4757 
4758         mutex_lock(&wq_pool_mutex);
4759 
4760         WARN_ON_ONCE(workqueue_freezing);
4761         workqueue_freezing = true;
4762 
4763         list_for_each_entry(wq, &workqueues, list) {
4764                 mutex_lock(&wq->mutex);
4765                 for_each_pwq(pwq, wq)
4766                         pwq_adjust_max_active(pwq);
4767                 mutex_unlock(&wq->mutex);
4768         }
4769 
4770         mutex_unlock(&wq_pool_mutex);
4771 }
4772 
4773 /**
4774  * freeze_workqueues_busy - are freezable workqueues still busy?
4775  *
4776  * Check whether freezing is complete.  This function must be called
4777  * between freeze_workqueues_begin() and thaw_workqueues().
4778  *
4779  * CONTEXT:
4780  * Grabs and releases wq_pool_mutex.
4781  *
4782  * Return:
4783  * %true if some freezable workqueues are still busy.  %false if freezing
4784  * is complete.
4785  */
4786 bool freeze_workqueues_busy(void)
4787 {
4788         bool busy = false;
4789         struct workqueue_struct *wq;
4790         struct pool_workqueue *pwq;
4791 
4792         mutex_lock(&wq_pool_mutex);
4793 
4794         WARN_ON_ONCE(!workqueue_freezing);
4795 
4796         list_for_each_entry(wq, &workqueues, list) {
4797                 if (!(wq->flags & WQ_FREEZABLE))
4798                         continue;
4799                 /*
4800                  * nr_active is monotonically decreasing.  It's safe
4801                  * to peek without lock.
4802                  */
4803                 rcu_read_lock_sched();
4804                 for_each_pwq(pwq, wq) {
4805                         WARN_ON_ONCE(pwq->nr_active < 0);
4806                         if (pwq->nr_active) {
4807                                 busy = true;
4808                                 rcu_read_unlock_sched();
4809                                 goto out_unlock;
4810                         }
4811                 }
4812                 rcu_read_unlock_sched();
4813         }
4814 out_unlock:
4815         mutex_unlock(&wq_pool_mutex);
4816         return busy;
4817 }
4818 
4819 /**
4820  * thaw_workqueues - thaw workqueues
4821  *
4822  * Thaw workqueues.  Normal queueing is restored and all collected
4823  * frozen works are transferred to their respective pool worklists.
4824  *
4825  * CONTEXT:
4826  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4827  */
4828 void thaw_workqueues(void)
4829 {
4830         struct workqueue_struct *wq;
4831         struct pool_workqueue *pwq;
4832 
4833         mutex_lock(&wq_pool_mutex);
4834 
4835         if (!workqueue_freezing)
4836                 goto out_unlock;
4837 
4838         workqueue_freezing = false;
4839 
4840         /* restore max_active and repopulate worklist */
4841         list_for_each_entry(wq, &workqueues, list) {
4842                 mutex_lock(&wq->mutex);
4843                 for_each_pwq(pwq, wq)
4844                         pwq_adjust_max_active(pwq);
4845                 mutex_unlock(&wq->mutex);
4846         }
4847 
4848 out_unlock:
4849         mutex_unlock(&wq_pool_mutex);
4850 }
4851 #endif /* CONFIG_FREEZER */
4852 
4853 static int workqueue_apply_unbound_cpumask(void)
4854 {
4855         LIST_HEAD(ctxs);
4856         int ret = 0;
4857         struct workqueue_struct *wq;
4858         struct apply_wqattrs_ctx *ctx, *n;
4859 
4860         lockdep_assert_held(&wq_pool_mutex);
4861 
4862         list_for_each_entry(wq, &workqueues, list) {
4863                 if (!(wq->flags & WQ_UNBOUND))
4864                         continue;
4865                 /* creating multiple pwqs breaks ordering guarantee */
4866                 if (wq->flags & __WQ_ORDERED)
4867                         continue;
4868 
4869                 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4870                 if (!ctx) {
4871                         ret = -ENOMEM;
4872                         break;
4873                 }
4874 
4875                 list_add_tail(&ctx->list, &ctxs);
4876         }
4877 
4878         list_for_each_entry_safe(ctx, n, &ctxs, list) {
4879                 if (!ret)
4880                         apply_wqattrs_commit(ctx);
4881                 apply_wqattrs_cleanup(ctx);
4882         }
4883 
4884         return ret;
4885 }
4886 
4887 /**
4888  *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4889  *  @cpumask: the cpumask to set
4890  *
4891  *  The low-level workqueues cpumask is a global cpumask that limits
4892  *  the affinity of all unbound workqueues.  This function check the @cpumask
4893  *  and apply it to all unbound workqueues and updates all pwqs of them.
4894  *
4895  *  Retun:      0       - Success
4896  *              -EINVAL - Invalid @cpumask
4897  *              -ENOMEM - Failed to allocate memory for attrs or pwqs.
4898  */
4899 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4900 {
4901         int ret = -EINVAL;
4902         cpumask_var_t saved_cpumask;
4903 
4904         if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4905                 return -ENOMEM;
4906 
4907         cpumask_and(cpumask, cpumask, cpu_possible_mask);
4908         if (!cpumask_empty(cpumask)) {
4909                 apply_wqattrs_lock();
4910 
4911                 /* save the old wq_unbound_cpumask. */
4912                 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4913 
4914                 /* update wq_unbound_cpumask at first and apply it to wqs. */
4915                 cpumask_copy(wq_unbound_cpumask, cpumask);
4916                 ret = workqueue_apply_unbound_cpumask();
4917 
4918                 /* restore the wq_unbound_cpumask when failed. */
4919                 if (ret < 0)
4920                         cpumask_copy(wq_unbound_cpumask, saved_cpumask);
4921 
4922                 apply_wqattrs_unlock();
4923         }
4924 
4925         free_cpumask_var(saved_cpumask);
4926         return ret;
4927 }
4928 
4929 #ifdef CONFIG_SYSFS
4930 /*
4931  * Workqueues with WQ_SYSFS flag set is visible to userland via
4932  * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
4933  * following attributes.
4934  *
4935  *  per_cpu     RO bool : whether the workqueue is per-cpu or unbound
4936  *  max_active  RW int  : maximum number of in-flight work items
4937  *
4938  * Unbound workqueues have the following extra attributes.
4939  *
4940  *  id          RO int  : the associated pool ID
4941  *  nice        RW int  : nice value of the workers
4942  *  cpumask     RW mask : bitmask of allowed CPUs for the workers
4943  */
4944 struct wq_device {
4945         struct workqueue_struct         *wq;
4946         struct device                   dev;
4947 };
4948 
4949 static struct workqueue_struct *dev_to_wq(struct device *dev)
4950 {
4951         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
4952 
4953         return wq_dev->wq;
4954 }
4955 
4956 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
4957                             char *buf)
4958 {
4959         struct workqueue_struct *wq = dev_to_wq(dev);
4960 
4961         return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
4962 }
4963 static DEVICE_ATTR_RO(per_cpu);
4964 
4965 static ssize_t max_active_show(struct device *dev,
4966                                struct device_attribute *attr, char *buf)
4967 {
4968         struct workqueue_struct *wq = dev_to_wq(dev);
4969 
4970         return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
4971 }
4972 
4973 static ssize_t max_active_store(struct device *dev,
4974                                 struct device_attribute *attr, const char *buf,
4975                                 size_t count)
4976 {
4977         struct workqueue_struct *wq = dev_to_wq(dev);
4978         int val;
4979 
4980         if (sscanf(buf, "%d", &val) != 1 || val <= 0)
4981                 return -EINVAL;
4982 
4983         workqueue_set_max_active(wq, val);
4984         return count;
4985 }
4986 static DEVICE_ATTR_RW(max_active);
4987 
4988 static struct attribute *wq_sysfs_attrs[] = {
4989         &dev_attr_per_cpu.attr,
4990         &dev_attr_max_active.attr,
4991         NULL,
4992 };
4993 ATTRIBUTE_GROUPS(wq_sysfs);
4994 
4995 static ssize_t wq_pool_ids_show(struct device *dev,
4996                                 struct device_attribute *attr, char *buf)
4997 {
4998         struct workqueue_struct *wq = dev_to_wq(dev);
4999         const char *delim = "";
5000         int node, written = 0;
5001 
5002         rcu_read_lock_sched();
5003         for_each_node(node) {
5004                 written += scnprintf(buf + written, PAGE_SIZE - written,
5005                                      "%s%d:%d", delim, node,
5006                                      unbound_pwq_by_node(wq, node)->pool->id);
5007                 delim = " ";
5008         }
5009         written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5010         rcu_read_unlock_sched();
5011 
5012         return written;
5013 }
5014 
5015 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5016                             char *buf)
5017 {
5018         struct workqueue_struct *wq = dev_to_wq(dev);
5019         int written;
5020 
5021         mutex_lock(&wq->mutex);
5022         written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5023         mutex_unlock(&wq->mutex);
5024 
5025         return written;
5026 }
5027 
5028 /* prepare workqueue_attrs for sysfs store operations */
5029 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5030 {
5031         struct workqueue_attrs *attrs;
5032 
5033         lockdep_assert_held(&wq_pool_mutex);
5034 
5035         attrs = alloc_workqueue_attrs(GFP_KERNEL);
5036         if (!attrs)
5037                 return NULL;
5038 
5039         copy_workqueue_attrs(attrs, wq->unbound_attrs);
5040         return attrs;
5041 }
5042 
5043 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5044                              const char *buf, size_t count)
5045 {
5046         struct workqueue_struct *wq = dev_to_wq(dev);
5047         struct workqueue_attrs *attrs;
5048         int ret = -ENOMEM;
5049 
5050         apply_wqattrs_lock();
5051 
5052         attrs = wq_sysfs_prep_attrs(wq);
5053         if (!attrs)
5054                 goto out_unlock;
5055 
5056         if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5057             attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5058                 ret = apply_workqueue_attrs_locked(wq, attrs);
5059         else
5060                 ret = -EINVAL;
5061 
5062 out_unlock:
5063         apply_wqattrs_unlock();
5064         free_workqueue_attrs(attrs);
5065         return ret ?: count;
5066 }
5067 
5068 static ssize_t wq_cpumask_show(struct device *dev,
5069                                struct device_attribute *attr, char *buf)
5070 {
5071         struct workqueue_struct *wq = dev_to_wq(dev);
5072         int written;
5073 
5074         mutex_lock(&wq->mutex);
5075         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5076                             cpumask_pr_args(wq->unbound_attrs->cpumask));
5077         mutex_unlock(&wq->mutex);
5078         return written;
5079 }
5080 
5081 static ssize_t wq_cpumask_store(struct device *dev,
5082                                 struct device_attribute *attr,
5083                                 const char *buf, size_t count)
5084 {
5085         struct workqueue_struct *wq = dev_to_wq(dev);
5086         struct workqueue_attrs *attrs;
5087         int ret = -ENOMEM;
5088 
5089         apply_wqattrs_lock();
5090 
5091         attrs = wq_sysfs_prep_attrs(wq);
5092         if (!attrs)
5093                 goto out_unlock;
5094 
5095         ret = cpumask_parse(buf, attrs->cpumask);
5096         if (!ret)
5097                 ret = apply_workqueue_attrs_locked(wq, attrs);
5098 
5099 out_unlock:
5100         apply_wqattrs_unlock();
5101         free_workqueue_attrs(attrs);
5102         return ret ?: count;
5103 }
5104 
5105 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5106                             char *buf)
5107 {
5108         struct workqueue_struct *wq = dev_to_wq(dev);
5109         int written;
5110 
5111         mutex_lock(&wq->mutex);
5112         written = scnprintf(buf, PAGE_SIZE, "%d\n",
5113                             !wq->unbound_attrs->no_numa);
5114         mutex_unlock(&wq->mutex);
5115 
5116         return written;
5117 }
5118 
5119 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5120                              const char *buf, size_t count)
5121 {
5122         struct workqueue_struct *wq = dev_to_wq(dev);
5123         struct workqueue_attrs *attrs;
5124         int v, ret = -ENOMEM;
5125 
5126         apply_wqattrs_lock();
5127 
5128         attrs = wq_sysfs_prep_attrs(wq);
5129         if (!attrs)
5130                 goto out_unlock;
5131 
5132         ret = -EINVAL;
5133         if (sscanf(buf, "%d", &v) == 1) {
5134                 attrs->no_numa = !v;
5135                 ret = apply_workqueue_attrs_locked(wq, attrs);
5136         }
5137 
5138 out_unlock:
5139         apply_wqattrs_unlock();
5140         free_workqueue_attrs(attrs);
5141         return ret ?: count;
5142 }
5143 
5144 static struct device_attribute wq_sysfs_unbound_attrs[] = {
5145         __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5146         __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5147         __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5148         __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5149         __ATTR_NULL,
5150 };
5151 
5152 static struct bus_type wq_subsys = {
5153         .name                           = "workqueue",
5154         .dev_groups                     = wq_sysfs_groups,
5155 };
5156 
5157 static ssize_t wq_unbound_cpumask_show(struct device *dev,
5158                 struct device_attribute *attr, char *buf)
5159 {
5160         int written;
5161 
5162         mutex_lock(&wq_pool_mutex);
5163         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5164                             cpumask_pr_args(wq_unbound_cpumask));
5165         mutex_unlock(&wq_pool_mutex);
5166 
5167         return written;
5168 }
5169 
5170 static ssize_t wq_unbound_cpumask_store(struct device *dev,
5171                 struct device_attribute *attr, const char *buf, size_t count)
5172 {
5173         cpumask_var_t cpumask;
5174         int ret;
5175 
5176         if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5177                 return -ENOMEM;
5178 
5179         ret = cpumask_parse(buf, cpumask);
5180         if (!ret)
5181                 ret = workqueue_set_unbound_cpumask(cpumask);
5182 
5183         free_cpumask_var(cpumask);
5184         return ret ? ret : count;
5185 }
5186 
5187 static struct device_attribute wq_sysfs_cpumask_attr =
5188         __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5189                wq_unbound_cpumask_store);
5190 
5191 static int __init wq_sysfs_init(void)
5192 {
5193         int err;
5194 
5195         err = subsys_virtual_register(&wq_subsys, NULL);
5196         if (err)
5197                 return err;
5198 
5199         return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5200 }
5201 core_initcall(wq_sysfs_init);
5202 
5203 static void wq_device_release(struct device *dev)
5204 {
5205         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5206 
5207         kfree(wq_dev);
5208 }
5209 
5210 /**
5211  * workqueue_sysfs_register - make a workqueue visible in sysfs
5212  * @wq: the workqueue to register
5213  *
5214  * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5215  * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5216  * which is the preferred method.
5217  *
5218  * Workqueue user should use this function directly iff it wants to apply
5219  * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5220  * apply_workqueue_attrs() may race against userland updating the
5221  * attributes.
5222  *
5223  * Return: 0 on success, -errno on failure.
5224  */
5225 int workqueue_sysfs_register(struct workqueue_struct *wq)
5226 {
5227         struct wq_device *wq_dev;
5228         int ret;
5229 
5230         /*
5231          * Adjusting max_active or creating new pwqs by applying
5232          * attributes breaks ordering guarantee.  Disallow exposing ordered
5233          * workqueues.
5234          */
5235         if (WARN_ON(wq->flags & __WQ_ORDERED))
5236                 return -EINVAL;
5237 
5238         wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5239         if (!wq_dev)
5240                 return -ENOMEM;
5241 
5242         wq_dev->wq = wq;
5243         wq_dev->dev.bus = &wq_subsys;
5244         wq_dev->dev.release = wq_device_release;
5245         dev_set_name(&wq_dev->dev, "%s", wq->name);
5246 
5247         /*
5248          * unbound_attrs are created separately.  Suppress uevent until
5249          * everything is ready.
5250          */
5251         dev_set_uevent_suppress(&wq_dev->dev, true);
5252 
5253         ret = device_register(&wq_dev->dev);
5254         if (ret) {
5255                 kfree(wq_dev);
5256                 wq->wq_dev = NULL;
5257                 return ret;
5258         }
5259 
5260         if (wq->flags & WQ_UNBOUND) {
5261                 struct device_attribute *attr;
5262 
5263                 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5264                         ret = device_create_file(&wq_dev->dev, attr);
5265                         if (ret) {
5266                                 device_unregister(&wq_dev->dev);
5267                                 wq->wq_dev = NULL;
5268                                 return ret;
5269                         }
5270                 }
5271         }
5272 
5273         dev_set_uevent_suppress(&wq_dev->dev, false);
5274         kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5275         return 0;
5276 }
5277 
5278 /**
5279  * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5280  * @wq: the workqueue to unregister
5281  *
5282  * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5283  */
5284 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5285 {
5286         struct wq_device *wq_dev = wq->wq_dev;
5287 
5288         if (!wq->wq_dev)
5289                 return;
5290 
5291         wq->wq_dev = NULL;
5292         device_unregister(&wq_dev->dev);
5293 }
5294 #else   /* CONFIG_SYSFS */
5295 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)     { }
5296 #endif  /* CONFIG_SYSFS */
5297 
5298 /*
5299  * Workqueue watchdog.
5300  *
5301  * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5302  * flush dependency, a concurrency managed work item which stays RUNNING
5303  * indefinitely.  Workqueue stalls can be very difficult to debug as the
5304  * usual warning mechanisms don't trigger and internal workqueue state is
5305  * largely opaque.
5306  *
5307  * Workqueue watchdog monitors all worker pools periodically and dumps
5308  * state if some pools failed to make forward progress for a while where
5309  * forward progress is defined as the first item on ->worklist changing.
5310  *
5311  * This mechanism is controlled through the kernel parameter
5312  * "workqueue.watchdog_thresh" which can be updated at runtime through the
5313  * corresponding sysfs parameter file.
5314  */
5315 #ifdef CONFIG_WQ_WATCHDOG
5316 
5317 static void wq_watchdog_timer_fn(unsigned long data);
5318 
5319 static unsigned long wq_watchdog_thresh = 30;
5320 static struct timer_list wq_watchdog_timer =
5321         TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0);
5322 
5323 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5324 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5325 
5326 static void wq_watchdog_reset_touched(void)
5327 {
5328         int cpu;
5329 
5330         wq_watchdog_touched = jiffies;
5331         for_each_possible_cpu(cpu)
5332                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5333 }
5334 
5335 static void wq_watchdog_timer_fn(unsigned long data)
5336 {
5337         unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5338         bool lockup_detected = false;
5339         struct worker_pool *pool;
5340         int pi;
5341 
5342         if (!thresh)
5343                 return;
5344 
5345         rcu_read_lock();
5346 
5347         for_each_pool(pool, pi) {
5348                 unsigned long pool_ts, touched, ts;
5349 
5350                 if (list_empty(&pool->worklist))
5351                         continue;
5352 
5353                 /* get the latest of pool and touched timestamps */
5354                 pool_ts = READ_ONCE(pool->watchdog_ts);
5355                 touched = READ_ONCE(wq_watchdog_touched);
5356 
5357                 if (time_after(pool_ts, touched))
5358                         ts = pool_ts;
5359                 else
5360                         ts = touched;
5361 
5362                 if (pool->cpu >= 0) {
5363                         unsigned long cpu_touched =
5364                                 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5365                                                   pool->cpu));
5366                         if (time_after(cpu_touched, ts))
5367                                 ts = cpu_touched;
5368                 }
5369 
5370                 /* did we stall? */
5371                 if (time_after(jiffies, ts + thresh)) {
5372                         lockup_detected = true;
5373                         pr_emerg("BUG: workqueue lockup - pool");
5374                         pr_cont_pool_info(pool);
5375                         pr_cont(" stuck for %us!\n",
5376                                 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5377                 }
5378         }
5379 
5380         rcu_read_unlock();
5381 
5382         if (lockup_detected)
5383                 show_workqueue_state();
5384 
5385         wq_watchdog_reset_touched();
5386         mod_timer(&wq_watchdog_timer, jiffies + thresh);
5387 }
5388 
5389 void wq_watchdog_touch(int cpu)
5390 {
5391         if (cpu >= 0)
5392                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5393         else
5394                 wq_watchdog_touched = jiffies;
5395 }
5396 
5397 static void wq_watchdog_set_thresh(unsigned long thresh)
5398 {
5399         wq_watchdog_thresh = 0;
5400         del_timer_sync(&wq_watchdog_timer);
5401 
5402         if (thresh) {
5403                 wq_watchdog_thresh = thresh;
5404                 wq_watchdog_reset_touched();
5405                 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5406         }
5407 }
5408 
5409 static int wq_watchdog_param_set_thresh(const char *val,
5410                                         const struct kernel_param *kp)
5411 {
5412         unsigned long thresh;
5413         int ret;
5414 
5415         ret = kstrtoul(val, 0, &thresh);
5416         if (ret)
5417                 return ret;
5418 
5419         if (system_wq)
5420                 wq_watchdog_set_thresh(thresh);
5421         else
5422                 wq_watchdog_thresh = thresh;
5423 
5424         return 0;
5425 }
5426 
5427 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5428         .set    = wq_watchdog_param_set_thresh,
5429         .get    = param_get_ulong,
5430 };
5431 
5432 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5433                 0644);
5434 
5435 static void wq_watchdog_init(void)
5436 {
5437         wq_watchdog_set_thresh(wq_watchdog_thresh);
5438 }
5439 
5440 #else   /* CONFIG_WQ_WATCHDOG */
5441 
5442 static inline void wq_watchdog_init(void) { }
5443 
5444 #endif  /* CONFIG_WQ_WATCHDOG */
5445 
5446 static void __init wq_numa_init(void)
5447 {
5448         cpumask_var_t *tbl;
5449         int node, cpu;
5450 
5451         if (num_possible_nodes() <= 1)
5452                 return;
5453 
5454         if (wq_disable_numa) {
5455                 pr_info("workqueue: NUMA affinity support disabled\n");
5456                 return;
5457         }
5458 
5459         wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5460         BUG_ON(!wq_update_unbound_numa_attrs_buf);
5461 
5462         /*
5463          * We want masks of possible CPUs of each node which isn't readily
5464          * available.  Build one from cpu_to_node() which should have been
5465          * fully initialized by now.
5466          */
5467         tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5468         BUG_ON(!tbl);
5469 
5470         for_each_node(node)
5471                 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5472                                 node_online(node) ? node : NUMA_NO_NODE));
5473 
5474         for_each_possible_cpu(cpu) {
5475                 node = cpu_to_node(cpu);
5476                 if (WARN_ON(node == NUMA_NO_NODE)) {
5477                         pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5478                         /* happens iff arch is bonkers, let's just proceed */
5479                         return;
5480                 }
5481                 cpumask_set_cpu(cpu, tbl[node]);
5482         }
5483 
5484         wq_numa_possible_cpumask = tbl;
5485         wq_numa_enabled = true;
5486 }
5487 
5488 /**
5489  * workqueue_init_early - early init for workqueue subsystem
5490  *
5491  * This is the first half of two-staged workqueue subsystem initialization
5492  * and invoked as soon as the bare basics - memory allocation, cpumasks and
5493  * idr are up.  It sets up all the data structures and system workqueues
5494  * and allows early boot code to create workqueues and queue/cancel work
5495  * items.  Actual work item execution starts only after kthreads can be
5496  * created and scheduled right before early initcalls.
5497  */
5498 int __init workqueue_init_early(void)
5499 {
5500         int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5501         int i, cpu;
5502 
5503         WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5504 
5505         BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5506         cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
5507 
5508         pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5509 
5510         /* initialize CPU pools */
5511         for_each_possible_cpu(cpu) {
5512                 struct worker_pool *pool;
5513 
5514                 i = 0;
5515                 for_each_cpu_worker_pool(pool, cpu) {
5516                         BUG_ON(init_worker_pool(pool));
5517                         pool->cpu = cpu;
5518                         cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5519                         pool->attrs->nice = std_nice[i++];
5520                         pool->node = cpu_to_node(cpu);
5521 
5522                         /* alloc pool ID */
5523                         mutex_lock(&wq_pool_mutex);
5524                         BUG_ON(worker_pool_assign_id(pool));
5525                         mutex_unlock(&wq_pool_mutex);
5526                 }
5527         }
5528 
5529         /* create default unbound and ordered wq attrs */
5530         for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5531                 struct workqueue_attrs *attrs;
5532 
5533                 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5534                 attrs->nice = std_nice[i];
5535                 unbound_std_wq_attrs[i] = attrs;
5536 
5537                 /*
5538                  * An ordered wq should have only one pwq as ordering is
5539                  * guaranteed by max_active which is enforced by pwqs.
5540                  * Turn off NUMA so that dfl_pwq is used for all nodes.
5541                  */
5542                 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5543                 attrs->nice = std_nice[i];
5544                 attrs->no_numa = true;
5545                 ordered_wq_attrs[i] = attrs;
5546         }
5547 
5548         system_wq = alloc_workqueue("events", 0, 0);
5549         system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5550         system_long_wq = alloc_workqueue("events_long", 0, 0);
5551         system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5552                                             WQ_UNBOUND_MAX_ACTIVE);
5553         system_freezable_wq = alloc_workqueue("events_freezable",
5554                                               WQ_FREEZABLE, 0);
5555         system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5556                                               WQ_POWER_EFFICIENT, 0);
5557         system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5558                                               WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5559                                               0);
5560         BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5561                !system_unbound_wq || !system_freezable_wq ||
5562                !system_power_efficient_wq ||
5563                !system_freezable_power_efficient_wq);
5564 
5565         return 0;
5566 }
5567 
5568 /**
5569  * workqueue_init - bring workqueue subsystem fully online
5570  *
5571  * This is the latter half of two-staged workqueue subsystem initialization
5572  * and invoked as soon as kthreads can be created and scheduled.
5573  * Workqueues have been created and work items queued on them, but there
5574  * are no kworkers executing the work items yet.  Populate the worker pools
5575  * with the initial workers and enable future kworker creations.
5576  */
5577 int __init workqueue_init(void)
5578 {
5579         struct workqueue_struct *wq;
5580         struct worker_pool *pool;
5581         int cpu, bkt;
5582 
5583         /*
5584          * It'd be simpler to initialize NUMA in workqueue_init_early() but
5585          * CPU to node mapping may not be available that early on some
5586          * archs such as power and arm64.  As per-cpu pools created
5587          * previously could be missing node hint and unbound pools NUMA
5588          * affinity, fix them up.
5589          */
5590         wq_numa_init();
5591 
5592         mutex_lock(&wq_pool_mutex);
5593 
5594         for_each_possible_cpu(cpu) {
5595                 for_each_cpu_worker_pool(pool, cpu) {
5596                         pool->node = cpu_to_node(cpu);
5597                 }
5598         }
5599 
5600         list_for_each_entry(wq, &workqueues, list)
5601                 wq_update_unbound_numa(wq, smp_processor_id(), true);
5602 
5603         mutex_unlock(&wq_pool_mutex);
5604 
5605         /* create the initial workers */
5606         for_each_online_cpu(cpu) {
5607                 for_each_cpu_worker_pool(pool, cpu) {
5608                         pool->flags &= ~POOL_DISASSOCIATED;
5609                         BUG_ON(!create_worker(pool));
5610                 }
5611         }
5612 
5613         hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5614                 BUG_ON(!create_worker(pool));
5615 
5616         wq_online = true;
5617         wq_watchdog_init();
5618 
5619         return 0;
5620 }
5621 

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