Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/kernel/kthread.c

  1 /* Kernel thread helper functions.
  2  *   Copyright (C) 2004 IBM Corporation, Rusty Russell.
  3  *
  4  * Creation is done via kthreadd, so that we get a clean environment
  5  * even if we're invoked from userspace (think modprobe, hotplug cpu,
  6  * etc.).
  7  */
  8 #include <linux/sched.h>
  9 #include <linux/kthread.h>
 10 #include <linux/completion.h>
 11 #include <linux/err.h>
 12 #include <linux/cpuset.h>
 13 #include <linux/unistd.h>
 14 #include <linux/file.h>
 15 #include <linux/export.h>
 16 #include <linux/mutex.h>
 17 #include <linux/slab.h>
 18 #include <linux/freezer.h>
 19 #include <linux/ptrace.h>
 20 #include <linux/uaccess.h>
 21 #include <trace/events/sched.h>
 22 
 23 static DEFINE_SPINLOCK(kthread_create_lock);
 24 static LIST_HEAD(kthread_create_list);
 25 struct task_struct *kthreadd_task;
 26 
 27 struct kthread_create_info
 28 {
 29         /* Information passed to kthread() from kthreadd. */
 30         int (*threadfn)(void *data);
 31         void *data;
 32         int node;
 33 
 34         /* Result passed back to kthread_create() from kthreadd. */
 35         struct task_struct *result;
 36         struct completion *done;
 37 
 38         struct list_head list;
 39 };
 40 
 41 struct kthread {
 42         unsigned long flags;
 43         unsigned int cpu;
 44         void *data;
 45         struct completion parked;
 46         struct completion exited;
 47 };
 48 
 49 enum KTHREAD_BITS {
 50         KTHREAD_IS_PER_CPU = 0,
 51         KTHREAD_SHOULD_STOP,
 52         KTHREAD_SHOULD_PARK,
 53         KTHREAD_IS_PARKED,
 54 };
 55 
 56 static inline void set_kthread_struct(void *kthread)
 57 {
 58         /*
 59          * We abuse ->set_child_tid to avoid the new member and because it
 60          * can't be wrongly copied by copy_process(). We also rely on fact
 61          * that the caller can't exec, so PF_KTHREAD can't be cleared.
 62          */
 63         current->set_child_tid = (__force void __user *)kthread;
 64 }
 65 
 66 static inline struct kthread *to_kthread(struct task_struct *k)
 67 {
 68         WARN_ON(!(k->flags & PF_KTHREAD));
 69         return (__force void *)k->set_child_tid;
 70 }
 71 
 72 void free_kthread_struct(struct task_struct *k)
 73 {
 74         /*
 75          * Can be NULL if this kthread was created by kernel_thread()
 76          * or if kmalloc() in kthread() failed.
 77          */
 78         kfree(to_kthread(k));
 79 }
 80 
 81 /**
 82  * kthread_should_stop - should this kthread return now?
 83  *
 84  * When someone calls kthread_stop() on your kthread, it will be woken
 85  * and this will return true.  You should then return, and your return
 86  * value will be passed through to kthread_stop().
 87  */
 88 bool kthread_should_stop(void)
 89 {
 90         return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
 91 }
 92 EXPORT_SYMBOL(kthread_should_stop);
 93 
 94 /**
 95  * kthread_should_park - should this kthread park now?
 96  *
 97  * When someone calls kthread_park() on your kthread, it will be woken
 98  * and this will return true.  You should then do the necessary
 99  * cleanup and call kthread_parkme()
100  *
101  * Similar to kthread_should_stop(), but this keeps the thread alive
102  * and in a park position. kthread_unpark() "restarts" the thread and
103  * calls the thread function again.
104  */
105 bool kthread_should_park(void)
106 {
107         return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
108 }
109 EXPORT_SYMBOL_GPL(kthread_should_park);
110 
111 /**
112  * kthread_freezable_should_stop - should this freezable kthread return now?
113  * @was_frozen: optional out parameter, indicates whether %current was frozen
114  *
115  * kthread_should_stop() for freezable kthreads, which will enter
116  * refrigerator if necessary.  This function is safe from kthread_stop() /
117  * freezer deadlock and freezable kthreads should use this function instead
118  * of calling try_to_freeze() directly.
119  */
120 bool kthread_freezable_should_stop(bool *was_frozen)
121 {
122         bool frozen = false;
123 
124         might_sleep();
125 
126         if (unlikely(freezing(current)))
127                 frozen = __refrigerator(true);
128 
129         if (was_frozen)
130                 *was_frozen = frozen;
131 
132         return kthread_should_stop();
133 }
134 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
135 
136 /**
137  * kthread_data - return data value specified on kthread creation
138  * @task: kthread task in question
139  *
140  * Return the data value specified when kthread @task was created.
141  * The caller is responsible for ensuring the validity of @task when
142  * calling this function.
143  */
144 void *kthread_data(struct task_struct *task)
145 {
146         return to_kthread(task)->data;
147 }
148 
149 /**
150  * kthread_probe_data - speculative version of kthread_data()
151  * @task: possible kthread task in question
152  *
153  * @task could be a kthread task.  Return the data value specified when it
154  * was created if accessible.  If @task isn't a kthread task or its data is
155  * inaccessible for any reason, %NULL is returned.  This function requires
156  * that @task itself is safe to dereference.
157  */
158 void *kthread_probe_data(struct task_struct *task)
159 {
160         struct kthread *kthread = to_kthread(task);
161         void *data = NULL;
162 
163         probe_kernel_read(&data, &kthread->data, sizeof(data));
164         return data;
165 }
166 
167 static void __kthread_parkme(struct kthread *self)
168 {
169         __set_current_state(TASK_PARKED);
170         while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
171                 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
172                         complete(&self->parked);
173                 schedule();
174                 __set_current_state(TASK_PARKED);
175         }
176         clear_bit(KTHREAD_IS_PARKED, &self->flags);
177         __set_current_state(TASK_RUNNING);
178 }
179 
180 void kthread_parkme(void)
181 {
182         __kthread_parkme(to_kthread(current));
183 }
184 EXPORT_SYMBOL_GPL(kthread_parkme);
185 
186 static int kthread(void *_create)
187 {
188         /* Copy data: it's on kthread's stack */
189         struct kthread_create_info *create = _create;
190         int (*threadfn)(void *data) = create->threadfn;
191         void *data = create->data;
192         struct completion *done;
193         struct kthread *self;
194         int ret;
195 
196         self = kmalloc(sizeof(*self), GFP_KERNEL);
197         set_kthread_struct(self);
198 
199         /* If user was SIGKILLed, I release the structure. */
200         done = xchg(&create->done, NULL);
201         if (!done) {
202                 kfree(create);
203                 do_exit(-EINTR);
204         }
205 
206         if (!self) {
207                 create->result = ERR_PTR(-ENOMEM);
208                 complete(done);
209                 do_exit(-ENOMEM);
210         }
211 
212         self->flags = 0;
213         self->data = data;
214         init_completion(&self->exited);
215         init_completion(&self->parked);
216         current->vfork_done = &self->exited;
217 
218         /* OK, tell user we're spawned, wait for stop or wakeup */
219         __set_current_state(TASK_UNINTERRUPTIBLE);
220         create->result = current;
221         complete(done);
222         schedule();
223 
224         ret = -EINTR;
225         if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
226                 __kthread_parkme(self);
227                 ret = threadfn(data);
228         }
229         do_exit(ret);
230 }
231 
232 /* called from do_fork() to get node information for about to be created task */
233 int tsk_fork_get_node(struct task_struct *tsk)
234 {
235 #ifdef CONFIG_NUMA
236         if (tsk == kthreadd_task)
237                 return tsk->pref_node_fork;
238 #endif
239         return NUMA_NO_NODE;
240 }
241 
242 static void create_kthread(struct kthread_create_info *create)
243 {
244         int pid;
245 
246 #ifdef CONFIG_NUMA
247         current->pref_node_fork = create->node;
248 #endif
249         /* We want our own signal handler (we take no signals by default). */
250         pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
251         if (pid < 0) {
252                 /* If user was SIGKILLed, I release the structure. */
253                 struct completion *done = xchg(&create->done, NULL);
254 
255                 if (!done) {
256                         kfree(create);
257                         return;
258                 }
259                 create->result = ERR_PTR(pid);
260                 complete(done);
261         }
262 }
263 
264 static __printf(4, 0)
265 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
266                                                     void *data, int node,
267                                                     const char namefmt[],
268                                                     va_list args)
269 {
270         DECLARE_COMPLETION_ONSTACK(done);
271         struct task_struct *task;
272         struct kthread_create_info *create = kmalloc(sizeof(*create),
273                                                      GFP_KERNEL);
274 
275         if (!create)
276                 return ERR_PTR(-ENOMEM);
277         create->threadfn = threadfn;
278         create->data = data;
279         create->node = node;
280         create->done = &done;
281 
282         spin_lock(&kthread_create_lock);
283         list_add_tail(&create->list, &kthread_create_list);
284         spin_unlock(&kthread_create_lock);
285 
286         wake_up_process(kthreadd_task);
287         /*
288          * Wait for completion in killable state, for I might be chosen by
289          * the OOM killer while kthreadd is trying to allocate memory for
290          * new kernel thread.
291          */
292         if (unlikely(wait_for_completion_killable(&done))) {
293                 /*
294                  * If I was SIGKILLed before kthreadd (or new kernel thread)
295                  * calls complete(), leave the cleanup of this structure to
296                  * that thread.
297                  */
298                 if (xchg(&create->done, NULL))
299                         return ERR_PTR(-EINTR);
300                 /*
301                  * kthreadd (or new kernel thread) will call complete()
302                  * shortly.
303                  */
304                 wait_for_completion(&done);
305         }
306         task = create->result;
307         if (!IS_ERR(task)) {
308                 static const struct sched_param param = { .sched_priority = 0 };
309 
310                 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
311                 /*
312                  * root may have changed our (kthreadd's) priority or CPU mask.
313                  * The kernel thread should not inherit these properties.
314                  */
315                 sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
316                 set_cpus_allowed_ptr(task, cpu_all_mask);
317         }
318         kfree(create);
319         return task;
320 }
321 
322 /**
323  * kthread_create_on_node - create a kthread.
324  * @threadfn: the function to run until signal_pending(current).
325  * @data: data ptr for @threadfn.
326  * @node: task and thread structures for the thread are allocated on this node
327  * @namefmt: printf-style name for the thread.
328  *
329  * Description: This helper function creates and names a kernel
330  * thread.  The thread will be stopped: use wake_up_process() to start
331  * it.  See also kthread_run().  The new thread has SCHED_NORMAL policy and
332  * is affine to all CPUs.
333  *
334  * If thread is going to be bound on a particular cpu, give its node
335  * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
336  * When woken, the thread will run @threadfn() with @data as its
337  * argument. @threadfn() can either call do_exit() directly if it is a
338  * standalone thread for which no one will call kthread_stop(), or
339  * return when 'kthread_should_stop()' is true (which means
340  * kthread_stop() has been called).  The return value should be zero
341  * or a negative error number; it will be passed to kthread_stop().
342  *
343  * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
344  */
345 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
346                                            void *data, int node,
347                                            const char namefmt[],
348                                            ...)
349 {
350         struct task_struct *task;
351         va_list args;
352 
353         va_start(args, namefmt);
354         task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
355         va_end(args);
356 
357         return task;
358 }
359 EXPORT_SYMBOL(kthread_create_on_node);
360 
361 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
362 {
363         unsigned long flags;
364 
365         if (!wait_task_inactive(p, state)) {
366                 WARN_ON(1);
367                 return;
368         }
369 
370         /* It's safe because the task is inactive. */
371         raw_spin_lock_irqsave(&p->pi_lock, flags);
372         do_set_cpus_allowed(p, mask);
373         p->flags |= PF_NO_SETAFFINITY;
374         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
375 }
376 
377 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
378 {
379         __kthread_bind_mask(p, cpumask_of(cpu), state);
380 }
381 
382 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
383 {
384         __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
385 }
386 
387 /**
388  * kthread_bind - bind a just-created kthread to a cpu.
389  * @p: thread created by kthread_create().
390  * @cpu: cpu (might not be online, must be possible) for @k to run on.
391  *
392  * Description: This function is equivalent to set_cpus_allowed(),
393  * except that @cpu doesn't need to be online, and the thread must be
394  * stopped (i.e., just returned from kthread_create()).
395  */
396 void kthread_bind(struct task_struct *p, unsigned int cpu)
397 {
398         __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
399 }
400 EXPORT_SYMBOL(kthread_bind);
401 
402 /**
403  * kthread_create_on_cpu - Create a cpu bound kthread
404  * @threadfn: the function to run until signal_pending(current).
405  * @data: data ptr for @threadfn.
406  * @cpu: The cpu on which the thread should be bound,
407  * @namefmt: printf-style name for the thread. Format is restricted
408  *           to "name.*%u". Code fills in cpu number.
409  *
410  * Description: This helper function creates and names a kernel thread
411  * The thread will be woken and put into park mode.
412  */
413 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
414                                           void *data, unsigned int cpu,
415                                           const char *namefmt)
416 {
417         struct task_struct *p;
418 
419         p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
420                                    cpu);
421         if (IS_ERR(p))
422                 return p;
423         kthread_bind(p, cpu);
424         /* CPU hotplug need to bind once again when unparking the thread. */
425         set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
426         to_kthread(p)->cpu = cpu;
427         return p;
428 }
429 
430 /**
431  * kthread_unpark - unpark a thread created by kthread_create().
432  * @k:          thread created by kthread_create().
433  *
434  * Sets kthread_should_park() for @k to return false, wakes it, and
435  * waits for it to return. If the thread is marked percpu then its
436  * bound to the cpu again.
437  */
438 void kthread_unpark(struct task_struct *k)
439 {
440         struct kthread *kthread = to_kthread(k);
441 
442         clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
443         /*
444          * We clear the IS_PARKED bit here as we don't wait
445          * until the task has left the park code. So if we'd
446          * park before that happens we'd see the IS_PARKED bit
447          * which might be about to be cleared.
448          */
449         if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
450                 /*
451                  * Newly created kthread was parked when the CPU was offline.
452                  * The binding was lost and we need to set it again.
453                  */
454                 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
455                         __kthread_bind(k, kthread->cpu, TASK_PARKED);
456                 wake_up_state(k, TASK_PARKED);
457         }
458 }
459 EXPORT_SYMBOL_GPL(kthread_unpark);
460 
461 /**
462  * kthread_park - park a thread created by kthread_create().
463  * @k: thread created by kthread_create().
464  *
465  * Sets kthread_should_park() for @k to return true, wakes it, and
466  * waits for it to return. This can also be called after kthread_create()
467  * instead of calling wake_up_process(): the thread will park without
468  * calling threadfn().
469  *
470  * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
471  * If called by the kthread itself just the park bit is set.
472  */
473 int kthread_park(struct task_struct *k)
474 {
475         struct kthread *kthread = to_kthread(k);
476 
477         if (WARN_ON(k->flags & PF_EXITING))
478                 return -ENOSYS;
479 
480         if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
481                 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
482                 if (k != current) {
483                         wake_up_process(k);
484                         wait_for_completion(&kthread->parked);
485                 }
486         }
487 
488         return 0;
489 }
490 EXPORT_SYMBOL_GPL(kthread_park);
491 
492 /**
493  * kthread_stop - stop a thread created by kthread_create().
494  * @k: thread created by kthread_create().
495  *
496  * Sets kthread_should_stop() for @k to return true, wakes it, and
497  * waits for it to exit. This can also be called after kthread_create()
498  * instead of calling wake_up_process(): the thread will exit without
499  * calling threadfn().
500  *
501  * If threadfn() may call do_exit() itself, the caller must ensure
502  * task_struct can't go away.
503  *
504  * Returns the result of threadfn(), or %-EINTR if wake_up_process()
505  * was never called.
506  */
507 int kthread_stop(struct task_struct *k)
508 {
509         struct kthread *kthread;
510         int ret;
511 
512         trace_sched_kthread_stop(k);
513 
514         get_task_struct(k);
515         kthread = to_kthread(k);
516         set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
517         kthread_unpark(k);
518         wake_up_process(k);
519         wait_for_completion(&kthread->exited);
520         ret = k->exit_code;
521         put_task_struct(k);
522 
523         trace_sched_kthread_stop_ret(ret);
524         return ret;
525 }
526 EXPORT_SYMBOL(kthread_stop);
527 
528 int kthreadd(void *unused)
529 {
530         struct task_struct *tsk = current;
531 
532         /* Setup a clean context for our children to inherit. */
533         set_task_comm(tsk, "kthreadd");
534         ignore_signals(tsk);
535         set_cpus_allowed_ptr(tsk, cpu_all_mask);
536         set_mems_allowed(node_states[N_MEMORY]);
537 
538         current->flags |= PF_NOFREEZE;
539 
540         for (;;) {
541                 set_current_state(TASK_INTERRUPTIBLE);
542                 if (list_empty(&kthread_create_list))
543                         schedule();
544                 __set_current_state(TASK_RUNNING);
545 
546                 spin_lock(&kthread_create_lock);
547                 while (!list_empty(&kthread_create_list)) {
548                         struct kthread_create_info *create;
549 
550                         create = list_entry(kthread_create_list.next,
551                                             struct kthread_create_info, list);
552                         list_del_init(&create->list);
553                         spin_unlock(&kthread_create_lock);
554 
555                         create_kthread(create);
556 
557                         spin_lock(&kthread_create_lock);
558                 }
559                 spin_unlock(&kthread_create_lock);
560         }
561 
562         return 0;
563 }
564 
565 void __kthread_init_worker(struct kthread_worker *worker,
566                                 const char *name,
567                                 struct lock_class_key *key)
568 {
569         memset(worker, 0, sizeof(struct kthread_worker));
570         spin_lock_init(&worker->lock);
571         lockdep_set_class_and_name(&worker->lock, key, name);
572         INIT_LIST_HEAD(&worker->work_list);
573         INIT_LIST_HEAD(&worker->delayed_work_list);
574 }
575 EXPORT_SYMBOL_GPL(__kthread_init_worker);
576 
577 /**
578  * kthread_worker_fn - kthread function to process kthread_worker
579  * @worker_ptr: pointer to initialized kthread_worker
580  *
581  * This function implements the main cycle of kthread worker. It processes
582  * work_list until it is stopped with kthread_stop(). It sleeps when the queue
583  * is empty.
584  *
585  * The works are not allowed to keep any locks, disable preemption or interrupts
586  * when they finish. There is defined a safe point for freezing when one work
587  * finishes and before a new one is started.
588  *
589  * Also the works must not be handled by more than one worker at the same time,
590  * see also kthread_queue_work().
591  */
592 int kthread_worker_fn(void *worker_ptr)
593 {
594         struct kthread_worker *worker = worker_ptr;
595         struct kthread_work *work;
596 
597         /*
598          * FIXME: Update the check and remove the assignment when all kthread
599          * worker users are created using kthread_create_worker*() functions.
600          */
601         WARN_ON(worker->task && worker->task != current);
602         worker->task = current;
603 
604         if (worker->flags & KTW_FREEZABLE)
605                 set_freezable();
606 
607 repeat:
608         set_current_state(TASK_INTERRUPTIBLE);  /* mb paired w/ kthread_stop */
609 
610         if (kthread_should_stop()) {
611                 __set_current_state(TASK_RUNNING);
612                 spin_lock_irq(&worker->lock);
613                 worker->task = NULL;
614                 spin_unlock_irq(&worker->lock);
615                 return 0;
616         }
617 
618         work = NULL;
619         spin_lock_irq(&worker->lock);
620         if (!list_empty(&worker->work_list)) {
621                 work = list_first_entry(&worker->work_list,
622                                         struct kthread_work, node);
623                 list_del_init(&work->node);
624         }
625         worker->current_work = work;
626         spin_unlock_irq(&worker->lock);
627 
628         if (work) {
629                 __set_current_state(TASK_RUNNING);
630                 work->func(work);
631         } else if (!freezing(current))
632                 schedule();
633 
634         try_to_freeze();
635         goto repeat;
636 }
637 EXPORT_SYMBOL_GPL(kthread_worker_fn);
638 
639 static __printf(3, 0) struct kthread_worker *
640 __kthread_create_worker(int cpu, unsigned int flags,
641                         const char namefmt[], va_list args)
642 {
643         struct kthread_worker *worker;
644         struct task_struct *task;
645         int node = -1;
646 
647         worker = kzalloc(sizeof(*worker), GFP_KERNEL);
648         if (!worker)
649                 return ERR_PTR(-ENOMEM);
650 
651         kthread_init_worker(worker);
652 
653         if (cpu >= 0)
654                 node = cpu_to_node(cpu);
655 
656         task = __kthread_create_on_node(kthread_worker_fn, worker,
657                                                 node, namefmt, args);
658         if (IS_ERR(task))
659                 goto fail_task;
660 
661         if (cpu >= 0)
662                 kthread_bind(task, cpu);
663 
664         worker->flags = flags;
665         worker->task = task;
666         wake_up_process(task);
667         return worker;
668 
669 fail_task:
670         kfree(worker);
671         return ERR_CAST(task);
672 }
673 
674 /**
675  * kthread_create_worker - create a kthread worker
676  * @flags: flags modifying the default behavior of the worker
677  * @namefmt: printf-style name for the kthread worker (task).
678  *
679  * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
680  * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
681  * when the worker was SIGKILLed.
682  */
683 struct kthread_worker *
684 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
685 {
686         struct kthread_worker *worker;
687         va_list args;
688 
689         va_start(args, namefmt);
690         worker = __kthread_create_worker(-1, flags, namefmt, args);
691         va_end(args);
692 
693         return worker;
694 }
695 EXPORT_SYMBOL(kthread_create_worker);
696 
697 /**
698  * kthread_create_worker_on_cpu - create a kthread worker and bind it
699  *      it to a given CPU and the associated NUMA node.
700  * @cpu: CPU number
701  * @flags: flags modifying the default behavior of the worker
702  * @namefmt: printf-style name for the kthread worker (task).
703  *
704  * Use a valid CPU number if you want to bind the kthread worker
705  * to the given CPU and the associated NUMA node.
706  *
707  * A good practice is to add the cpu number also into the worker name.
708  * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
709  *
710  * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
711  * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
712  * when the worker was SIGKILLed.
713  */
714 struct kthread_worker *
715 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
716                              const char namefmt[], ...)
717 {
718         struct kthread_worker *worker;
719         va_list args;
720 
721         va_start(args, namefmt);
722         worker = __kthread_create_worker(cpu, flags, namefmt, args);
723         va_end(args);
724 
725         return worker;
726 }
727 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
728 
729 /*
730  * Returns true when the work could not be queued at the moment.
731  * It happens when it is already pending in a worker list
732  * or when it is being cancelled.
733  */
734 static inline bool queuing_blocked(struct kthread_worker *worker,
735                                    struct kthread_work *work)
736 {
737         lockdep_assert_held(&worker->lock);
738 
739         return !list_empty(&work->node) || work->canceling;
740 }
741 
742 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
743                                              struct kthread_work *work)
744 {
745         lockdep_assert_held(&worker->lock);
746         WARN_ON_ONCE(!list_empty(&work->node));
747         /* Do not use a work with >1 worker, see kthread_queue_work() */
748         WARN_ON_ONCE(work->worker && work->worker != worker);
749 }
750 
751 /* insert @work before @pos in @worker */
752 static void kthread_insert_work(struct kthread_worker *worker,
753                                 struct kthread_work *work,
754                                 struct list_head *pos)
755 {
756         kthread_insert_work_sanity_check(worker, work);
757 
758         list_add_tail(&work->node, pos);
759         work->worker = worker;
760         if (!worker->current_work && likely(worker->task))
761                 wake_up_process(worker->task);
762 }
763 
764 /**
765  * kthread_queue_work - queue a kthread_work
766  * @worker: target kthread_worker
767  * @work: kthread_work to queue
768  *
769  * Queue @work to work processor @task for async execution.  @task
770  * must have been created with kthread_worker_create().  Returns %true
771  * if @work was successfully queued, %false if it was already pending.
772  *
773  * Reinitialize the work if it needs to be used by another worker.
774  * For example, when the worker was stopped and started again.
775  */
776 bool kthread_queue_work(struct kthread_worker *worker,
777                         struct kthread_work *work)
778 {
779         bool ret = false;
780         unsigned long flags;
781 
782         spin_lock_irqsave(&worker->lock, flags);
783         if (!queuing_blocked(worker, work)) {
784                 kthread_insert_work(worker, work, &worker->work_list);
785                 ret = true;
786         }
787         spin_unlock_irqrestore(&worker->lock, flags);
788         return ret;
789 }
790 EXPORT_SYMBOL_GPL(kthread_queue_work);
791 
792 /**
793  * kthread_delayed_work_timer_fn - callback that queues the associated kthread
794  *      delayed work when the timer expires.
795  * @__data: pointer to the data associated with the timer
796  *
797  * The format of the function is defined by struct timer_list.
798  * It should have been called from irqsafe timer with irq already off.
799  */
800 void kthread_delayed_work_timer_fn(unsigned long __data)
801 {
802         struct kthread_delayed_work *dwork =
803                 (struct kthread_delayed_work *)__data;
804         struct kthread_work *work = &dwork->work;
805         struct kthread_worker *worker = work->worker;
806 
807         /*
808          * This might happen when a pending work is reinitialized.
809          * It means that it is used a wrong way.
810          */
811         if (WARN_ON_ONCE(!worker))
812                 return;
813 
814         spin_lock(&worker->lock);
815         /* Work must not be used with >1 worker, see kthread_queue_work(). */
816         WARN_ON_ONCE(work->worker != worker);
817 
818         /* Move the work from worker->delayed_work_list. */
819         WARN_ON_ONCE(list_empty(&work->node));
820         list_del_init(&work->node);
821         kthread_insert_work(worker, work, &worker->work_list);
822 
823         spin_unlock(&worker->lock);
824 }
825 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
826 
827 void __kthread_queue_delayed_work(struct kthread_worker *worker,
828                                   struct kthread_delayed_work *dwork,
829                                   unsigned long delay)
830 {
831         struct timer_list *timer = &dwork->timer;
832         struct kthread_work *work = &dwork->work;
833 
834         WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
835                      timer->data != (unsigned long)dwork);
836 
837         /*
838          * If @delay is 0, queue @dwork->work immediately.  This is for
839          * both optimization and correctness.  The earliest @timer can
840          * expire is on the closest next tick and delayed_work users depend
841          * on that there's no such delay when @delay is 0.
842          */
843         if (!delay) {
844                 kthread_insert_work(worker, work, &worker->work_list);
845                 return;
846         }
847 
848         /* Be paranoid and try to detect possible races already now. */
849         kthread_insert_work_sanity_check(worker, work);
850 
851         list_add(&work->node, &worker->delayed_work_list);
852         work->worker = worker;
853         timer_stats_timer_set_start_info(&dwork->timer);
854         timer->expires = jiffies + delay;
855         add_timer(timer);
856 }
857 
858 /**
859  * kthread_queue_delayed_work - queue the associated kthread work
860  *      after a delay.
861  * @worker: target kthread_worker
862  * @dwork: kthread_delayed_work to queue
863  * @delay: number of jiffies to wait before queuing
864  *
865  * If the work has not been pending it starts a timer that will queue
866  * the work after the given @delay. If @delay is zero, it queues the
867  * work immediately.
868  *
869  * Return: %false if the @work has already been pending. It means that
870  * either the timer was running or the work was queued. It returns %true
871  * otherwise.
872  */
873 bool kthread_queue_delayed_work(struct kthread_worker *worker,
874                                 struct kthread_delayed_work *dwork,
875                                 unsigned long delay)
876 {
877         struct kthread_work *work = &dwork->work;
878         unsigned long flags;
879         bool ret = false;
880 
881         spin_lock_irqsave(&worker->lock, flags);
882 
883         if (!queuing_blocked(worker, work)) {
884                 __kthread_queue_delayed_work(worker, dwork, delay);
885                 ret = true;
886         }
887 
888         spin_unlock_irqrestore(&worker->lock, flags);
889         return ret;
890 }
891 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
892 
893 struct kthread_flush_work {
894         struct kthread_work     work;
895         struct completion       done;
896 };
897 
898 static void kthread_flush_work_fn(struct kthread_work *work)
899 {
900         struct kthread_flush_work *fwork =
901                 container_of(work, struct kthread_flush_work, work);
902         complete(&fwork->done);
903 }
904 
905 /**
906  * kthread_flush_work - flush a kthread_work
907  * @work: work to flush
908  *
909  * If @work is queued or executing, wait for it to finish execution.
910  */
911 void kthread_flush_work(struct kthread_work *work)
912 {
913         struct kthread_flush_work fwork = {
914                 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
915                 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
916         };
917         struct kthread_worker *worker;
918         bool noop = false;
919 
920         worker = work->worker;
921         if (!worker)
922                 return;
923 
924         spin_lock_irq(&worker->lock);
925         /* Work must not be used with >1 worker, see kthread_queue_work(). */
926         WARN_ON_ONCE(work->worker != worker);
927 
928         if (!list_empty(&work->node))
929                 kthread_insert_work(worker, &fwork.work, work->node.next);
930         else if (worker->current_work == work)
931                 kthread_insert_work(worker, &fwork.work,
932                                     worker->work_list.next);
933         else
934                 noop = true;
935 
936         spin_unlock_irq(&worker->lock);
937 
938         if (!noop)
939                 wait_for_completion(&fwork.done);
940 }
941 EXPORT_SYMBOL_GPL(kthread_flush_work);
942 
943 /*
944  * This function removes the work from the worker queue. Also it makes sure
945  * that it won't get queued later via the delayed work's timer.
946  *
947  * The work might still be in use when this function finishes. See the
948  * current_work proceed by the worker.
949  *
950  * Return: %true if @work was pending and successfully canceled,
951  *      %false if @work was not pending
952  */
953 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
954                                   unsigned long *flags)
955 {
956         /* Try to cancel the timer if exists. */
957         if (is_dwork) {
958                 struct kthread_delayed_work *dwork =
959                         container_of(work, struct kthread_delayed_work, work);
960                 struct kthread_worker *worker = work->worker;
961 
962                 /*
963                  * del_timer_sync() must be called to make sure that the timer
964                  * callback is not running. The lock must be temporary released
965                  * to avoid a deadlock with the callback. In the meantime,
966                  * any queuing is blocked by setting the canceling counter.
967                  */
968                 work->canceling++;
969                 spin_unlock_irqrestore(&worker->lock, *flags);
970                 del_timer_sync(&dwork->timer);
971                 spin_lock_irqsave(&worker->lock, *flags);
972                 work->canceling--;
973         }
974 
975         /*
976          * Try to remove the work from a worker list. It might either
977          * be from worker->work_list or from worker->delayed_work_list.
978          */
979         if (!list_empty(&work->node)) {
980                 list_del_init(&work->node);
981                 return true;
982         }
983 
984         return false;
985 }
986 
987 /**
988  * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
989  * @worker: kthread worker to use
990  * @dwork: kthread delayed work to queue
991  * @delay: number of jiffies to wait before queuing
992  *
993  * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
994  * modify @dwork's timer so that it expires after @delay. If @delay is zero,
995  * @work is guaranteed to be queued immediately.
996  *
997  * Return: %true if @dwork was pending and its timer was modified,
998  * %false otherwise.
999  *
1000  * A special case is when the work is being canceled in parallel.
1001  * It might be caused either by the real kthread_cancel_delayed_work_sync()
1002  * or yet another kthread_mod_delayed_work() call. We let the other command
1003  * win and return %false here. The caller is supposed to synchronize these
1004  * operations a reasonable way.
1005  *
1006  * This function is safe to call from any context including IRQ handler.
1007  * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1008  * for details.
1009  */
1010 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1011                               struct kthread_delayed_work *dwork,
1012                               unsigned long delay)
1013 {
1014         struct kthread_work *work = &dwork->work;
1015         unsigned long flags;
1016         int ret = false;
1017 
1018         spin_lock_irqsave(&worker->lock, flags);
1019 
1020         /* Do not bother with canceling when never queued. */
1021         if (!work->worker)
1022                 goto fast_queue;
1023 
1024         /* Work must not be used with >1 worker, see kthread_queue_work() */
1025         WARN_ON_ONCE(work->worker != worker);
1026 
1027         /* Do not fight with another command that is canceling this work. */
1028         if (work->canceling)
1029                 goto out;
1030 
1031         ret = __kthread_cancel_work(work, true, &flags);
1032 fast_queue:
1033         __kthread_queue_delayed_work(worker, dwork, delay);
1034 out:
1035         spin_unlock_irqrestore(&worker->lock, flags);
1036         return ret;
1037 }
1038 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1039 
1040 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1041 {
1042         struct kthread_worker *worker = work->worker;
1043         unsigned long flags;
1044         int ret = false;
1045 
1046         if (!worker)
1047                 goto out;
1048 
1049         spin_lock_irqsave(&worker->lock, flags);
1050         /* Work must not be used with >1 worker, see kthread_queue_work(). */
1051         WARN_ON_ONCE(work->worker != worker);
1052 
1053         ret = __kthread_cancel_work(work, is_dwork, &flags);
1054 
1055         if (worker->current_work != work)
1056                 goto out_fast;
1057 
1058         /*
1059          * The work is in progress and we need to wait with the lock released.
1060          * In the meantime, block any queuing by setting the canceling counter.
1061          */
1062         work->canceling++;
1063         spin_unlock_irqrestore(&worker->lock, flags);
1064         kthread_flush_work(work);
1065         spin_lock_irqsave(&worker->lock, flags);
1066         work->canceling--;
1067 
1068 out_fast:
1069         spin_unlock_irqrestore(&worker->lock, flags);
1070 out:
1071         return ret;
1072 }
1073 
1074 /**
1075  * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1076  * @work: the kthread work to cancel
1077  *
1078  * Cancel @work and wait for its execution to finish.  This function
1079  * can be used even if the work re-queues itself. On return from this
1080  * function, @work is guaranteed to be not pending or executing on any CPU.
1081  *
1082  * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1083  * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1084  *
1085  * The caller must ensure that the worker on which @work was last
1086  * queued can't be destroyed before this function returns.
1087  *
1088  * Return: %true if @work was pending, %false otherwise.
1089  */
1090 bool kthread_cancel_work_sync(struct kthread_work *work)
1091 {
1092         return __kthread_cancel_work_sync(work, false);
1093 }
1094 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1095 
1096 /**
1097  * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1098  *      wait for it to finish.
1099  * @dwork: the kthread delayed work to cancel
1100  *
1101  * This is kthread_cancel_work_sync() for delayed works.
1102  *
1103  * Return: %true if @dwork was pending, %false otherwise.
1104  */
1105 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1106 {
1107         return __kthread_cancel_work_sync(&dwork->work, true);
1108 }
1109 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1110 
1111 /**
1112  * kthread_flush_worker - flush all current works on a kthread_worker
1113  * @worker: worker to flush
1114  *
1115  * Wait until all currently executing or pending works on @worker are
1116  * finished.
1117  */
1118 void kthread_flush_worker(struct kthread_worker *worker)
1119 {
1120         struct kthread_flush_work fwork = {
1121                 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1122                 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1123         };
1124 
1125         kthread_queue_work(worker, &fwork.work);
1126         wait_for_completion(&fwork.done);
1127 }
1128 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1129 
1130 /**
1131  * kthread_destroy_worker - destroy a kthread worker
1132  * @worker: worker to be destroyed
1133  *
1134  * Flush and destroy @worker.  The simple flush is enough because the kthread
1135  * worker API is used only in trivial scenarios.  There are no multi-step state
1136  * machines needed.
1137  */
1138 void kthread_destroy_worker(struct kthread_worker *worker)
1139 {
1140         struct task_struct *task;
1141 
1142         task = worker->task;
1143         if (WARN_ON(!task))
1144                 return;
1145 
1146         kthread_flush_worker(worker);
1147         kthread_stop(task);
1148         WARN_ON(!list_empty(&worker->work_list));
1149         kfree(worker);
1150 }
1151 EXPORT_SYMBOL(kthread_destroy_worker);
1152 

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