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/exit.c

  1 /*
  2  *  linux/kernel/exit.c
  3  *
  4  *  Copyright (C) 1991, 1992  Linus Torvalds
  5  */
  6 
  7 #include <linux/mm.h>
  8 #include <linux/slab.h>
  9 #include <linux/interrupt.h>
 10 #include <linux/module.h>
 11 #include <linux/capability.h>
 12 #include <linux/completion.h>
 13 #include <linux/personality.h>
 14 #include <linux/tty.h>
 15 #include <linux/iocontext.h>
 16 #include <linux/key.h>
 17 #include <linux/security.h>
 18 #include <linux/cpu.h>
 19 #include <linux/acct.h>
 20 #include <linux/tsacct_kern.h>
 21 #include <linux/file.h>
 22 #include <linux/fdtable.h>
 23 #include <linux/freezer.h>
 24 #include <linux/binfmts.h>
 25 #include <linux/nsproxy.h>
 26 #include <linux/pid_namespace.h>
 27 #include <linux/ptrace.h>
 28 #include <linux/profile.h>
 29 #include <linux/mount.h>
 30 #include <linux/proc_fs.h>
 31 #include <linux/kthread.h>
 32 #include <linux/mempolicy.h>
 33 #include <linux/taskstats_kern.h>
 34 #include <linux/delayacct.h>
 35 #include <linux/cgroup.h>
 36 #include <linux/syscalls.h>
 37 #include <linux/signal.h>
 38 #include <linux/posix-timers.h>
 39 #include <linux/cn_proc.h>
 40 #include <linux/mutex.h>
 41 #include <linux/futex.h>
 42 #include <linux/pipe_fs_i.h>
 43 #include <linux/audit.h> /* for audit_free() */
 44 #include <linux/resource.h>
 45 #include <linux/blkdev.h>
 46 #include <linux/task_io_accounting_ops.h>
 47 #include <linux/tracehook.h>
 48 #include <linux/fs_struct.h>
 49 #include <linux/init_task.h>
 50 #include <linux/perf_event.h>
 51 #include <trace/events/sched.h>
 52 #include <linux/hw_breakpoint.h>
 53 #include <linux/oom.h>
 54 #include <linux/writeback.h>
 55 #include <linux/shm.h>
 56 #include <linux/kcov.h>
 57 #include <linux/random.h>
 58 
 59 #include <linux/uaccess.h>
 60 #include <asm/unistd.h>
 61 #include <asm/pgtable.h>
 62 #include <asm/mmu_context.h>
 63 
 64 static void __unhash_process(struct task_struct *p, bool group_dead)
 65 {
 66         nr_threads--;
 67         detach_pid(p, PIDTYPE_PID);
 68         if (group_dead) {
 69                 detach_pid(p, PIDTYPE_PGID);
 70                 detach_pid(p, PIDTYPE_SID);
 71 
 72                 list_del_rcu(&p->tasks);
 73                 list_del_init(&p->sibling);
 74                 __this_cpu_dec(process_counts);
 75         }
 76         list_del_rcu(&p->thread_group);
 77         list_del_rcu(&p->thread_node);
 78 }
 79 
 80 /*
 81  * This function expects the tasklist_lock write-locked.
 82  */
 83 static void __exit_signal(struct task_struct *tsk)
 84 {
 85         struct signal_struct *sig = tsk->signal;
 86         bool group_dead = thread_group_leader(tsk);
 87         struct sighand_struct *sighand;
 88         struct tty_struct *uninitialized_var(tty);
 89         cputime_t utime, stime;
 90 
 91         sighand = rcu_dereference_check(tsk->sighand,
 92                                         lockdep_tasklist_lock_is_held());
 93         spin_lock(&sighand->siglock);
 94 
 95 #ifdef CONFIG_POSIX_TIMERS
 96         posix_cpu_timers_exit(tsk);
 97         if (group_dead) {
 98                 posix_cpu_timers_exit_group(tsk);
 99         } else {
100                 /*
101                  * This can only happen if the caller is de_thread().
102                  * FIXME: this is the temporary hack, we should teach
103                  * posix-cpu-timers to handle this case correctly.
104                  */
105                 if (unlikely(has_group_leader_pid(tsk)))
106                         posix_cpu_timers_exit_group(tsk);
107         }
108 #endif
109 
110         if (group_dead) {
111                 tty = sig->tty;
112                 sig->tty = NULL;
113         } else {
114                 /*
115                  * If there is any task waiting for the group exit
116                  * then notify it:
117                  */
118                 if (sig->notify_count > 0 && !--sig->notify_count)
119                         wake_up_process(sig->group_exit_task);
120 
121                 if (tsk == sig->curr_target)
122                         sig->curr_target = next_thread(tsk);
123         }
124 
125         add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
126                               sizeof(unsigned long long));
127 
128         /*
129          * Accumulate here the counters for all threads as they die. We could
130          * skip the group leader because it is the last user of signal_struct,
131          * but we want to avoid the race with thread_group_cputime() which can
132          * see the empty ->thread_head list.
133          */
134         task_cputime(tsk, &utime, &stime);
135         write_seqlock(&sig->stats_lock);
136         sig->utime += utime;
137         sig->stime += stime;
138         sig->gtime += task_gtime(tsk);
139         sig->min_flt += tsk->min_flt;
140         sig->maj_flt += tsk->maj_flt;
141         sig->nvcsw += tsk->nvcsw;
142         sig->nivcsw += tsk->nivcsw;
143         sig->inblock += task_io_get_inblock(tsk);
144         sig->oublock += task_io_get_oublock(tsk);
145         task_io_accounting_add(&sig->ioac, &tsk->ioac);
146         sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
147         sig->nr_threads--;
148         __unhash_process(tsk, group_dead);
149         write_sequnlock(&sig->stats_lock);
150 
151         /*
152          * Do this under ->siglock, we can race with another thread
153          * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
154          */
155         flush_sigqueue(&tsk->pending);
156         tsk->sighand = NULL;
157         spin_unlock(&sighand->siglock);
158 
159         __cleanup_sighand(sighand);
160         clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
161         if (group_dead) {
162                 flush_sigqueue(&sig->shared_pending);
163                 tty_kref_put(tty);
164         }
165 }
166 
167 static void delayed_put_task_struct(struct rcu_head *rhp)
168 {
169         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
170 
171         perf_event_delayed_put(tsk);
172         trace_sched_process_free(tsk);
173         put_task_struct(tsk);
174 }
175 
176 
177 void release_task(struct task_struct *p)
178 {
179         struct task_struct *leader;
180         int zap_leader;
181 repeat:
182         /* don't need to get the RCU readlock here - the process is dead and
183          * can't be modifying its own credentials. But shut RCU-lockdep up */
184         rcu_read_lock();
185         atomic_dec(&__task_cred(p)->user->processes);
186         rcu_read_unlock();
187 
188         proc_flush_task(p);
189 
190         write_lock_irq(&tasklist_lock);
191         ptrace_release_task(p);
192         __exit_signal(p);
193 
194         /*
195          * If we are the last non-leader member of the thread
196          * group, and the leader is zombie, then notify the
197          * group leader's parent process. (if it wants notification.)
198          */
199         zap_leader = 0;
200         leader = p->group_leader;
201         if (leader != p && thread_group_empty(leader)
202                         && leader->exit_state == EXIT_ZOMBIE) {
203                 /*
204                  * If we were the last child thread and the leader has
205                  * exited already, and the leader's parent ignores SIGCHLD,
206                  * then we are the one who should release the leader.
207                  */
208                 zap_leader = do_notify_parent(leader, leader->exit_signal);
209                 if (zap_leader)
210                         leader->exit_state = EXIT_DEAD;
211         }
212 
213         write_unlock_irq(&tasklist_lock);
214         release_thread(p);
215         call_rcu(&p->rcu, delayed_put_task_struct);
216 
217         p = leader;
218         if (unlikely(zap_leader))
219                 goto repeat;
220 }
221 
222 /*
223  * Note that if this function returns a valid task_struct pointer (!NULL)
224  * task->usage must remain >0 for the duration of the RCU critical section.
225  */
226 struct task_struct *task_rcu_dereference(struct task_struct **ptask)
227 {
228         struct sighand_struct *sighand;
229         struct task_struct *task;
230 
231         /*
232          * We need to verify that release_task() was not called and thus
233          * delayed_put_task_struct() can't run and drop the last reference
234          * before rcu_read_unlock(). We check task->sighand != NULL,
235          * but we can read the already freed and reused memory.
236          */
237 retry:
238         task = rcu_dereference(*ptask);
239         if (!task)
240                 return NULL;
241 
242         probe_kernel_address(&task->sighand, sighand);
243 
244         /*
245          * Pairs with atomic_dec_and_test() in put_task_struct(). If this task
246          * was already freed we can not miss the preceding update of this
247          * pointer.
248          */
249         smp_rmb();
250         if (unlikely(task != READ_ONCE(*ptask)))
251                 goto retry;
252 
253         /*
254          * We've re-checked that "task == *ptask", now we have two different
255          * cases:
256          *
257          * 1. This is actually the same task/task_struct. In this case
258          *    sighand != NULL tells us it is still alive.
259          *
260          * 2. This is another task which got the same memory for task_struct.
261          *    We can't know this of course, and we can not trust
262          *    sighand != NULL.
263          *
264          *    In this case we actually return a random value, but this is
265          *    correct.
266          *
267          *    If we return NULL - we can pretend that we actually noticed that
268          *    *ptask was updated when the previous task has exited. Or pretend
269          *    that probe_slab_address(&sighand) reads NULL.
270          *
271          *    If we return the new task (because sighand is not NULL for any
272          *    reason) - this is fine too. This (new) task can't go away before
273          *    another gp pass.
274          *
275          *    And note: We could even eliminate the false positive if re-read
276          *    task->sighand once again to avoid the falsely NULL. But this case
277          *    is very unlikely so we don't care.
278          */
279         if (!sighand)
280                 return NULL;
281 
282         return task;
283 }
284 
285 struct task_struct *try_get_task_struct(struct task_struct **ptask)
286 {
287         struct task_struct *task;
288 
289         rcu_read_lock();
290         task = task_rcu_dereference(ptask);
291         if (task)
292                 get_task_struct(task);
293         rcu_read_unlock();
294 
295         return task;
296 }
297 
298 /*
299  * Determine if a process group is "orphaned", according to the POSIX
300  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
301  * by terminal-generated stop signals.  Newly orphaned process groups are
302  * to receive a SIGHUP and a SIGCONT.
303  *
304  * "I ask you, have you ever known what it is to be an orphan?"
305  */
306 static int will_become_orphaned_pgrp(struct pid *pgrp,
307                                         struct task_struct *ignored_task)
308 {
309         struct task_struct *p;
310 
311         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
312                 if ((p == ignored_task) ||
313                     (p->exit_state && thread_group_empty(p)) ||
314                     is_global_init(p->real_parent))
315                         continue;
316 
317                 if (task_pgrp(p->real_parent) != pgrp &&
318                     task_session(p->real_parent) == task_session(p))
319                         return 0;
320         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
321 
322         return 1;
323 }
324 
325 int is_current_pgrp_orphaned(void)
326 {
327         int retval;
328 
329         read_lock(&tasklist_lock);
330         retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
331         read_unlock(&tasklist_lock);
332 
333         return retval;
334 }
335 
336 static bool has_stopped_jobs(struct pid *pgrp)
337 {
338         struct task_struct *p;
339 
340         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
341                 if (p->signal->flags & SIGNAL_STOP_STOPPED)
342                         return true;
343         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
344 
345         return false;
346 }
347 
348 /*
349  * Check to see if any process groups have become orphaned as
350  * a result of our exiting, and if they have any stopped jobs,
351  * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
352  */
353 static void
354 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
355 {
356         struct pid *pgrp = task_pgrp(tsk);
357         struct task_struct *ignored_task = tsk;
358 
359         if (!parent)
360                 /* exit: our father is in a different pgrp than
361                  * we are and we were the only connection outside.
362                  */
363                 parent = tsk->real_parent;
364         else
365                 /* reparent: our child is in a different pgrp than
366                  * we are, and it was the only connection outside.
367                  */
368                 ignored_task = NULL;
369 
370         if (task_pgrp(parent) != pgrp &&
371             task_session(parent) == task_session(tsk) &&
372             will_become_orphaned_pgrp(pgrp, ignored_task) &&
373             has_stopped_jobs(pgrp)) {
374                 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
375                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
376         }
377 }
378 
379 #ifdef CONFIG_MEMCG
380 /*
381  * A task is exiting.   If it owned this mm, find a new owner for the mm.
382  */
383 void mm_update_next_owner(struct mm_struct *mm)
384 {
385         struct task_struct *c, *g, *p = current;
386 
387 retry:
388         /*
389          * If the exiting or execing task is not the owner, it's
390          * someone else's problem.
391          */
392         if (mm->owner != p)
393                 return;
394         /*
395          * The current owner is exiting/execing and there are no other
396          * candidates.  Do not leave the mm pointing to a possibly
397          * freed task structure.
398          */
399         if (atomic_read(&mm->mm_users) <= 1) {
400                 mm->owner = NULL;
401                 return;
402         }
403 
404         read_lock(&tasklist_lock);
405         /*
406          * Search in the children
407          */
408         list_for_each_entry(c, &p->children, sibling) {
409                 if (c->mm == mm)
410                         goto assign_new_owner;
411         }
412 
413         /*
414          * Search in the siblings
415          */
416         list_for_each_entry(c, &p->real_parent->children, sibling) {
417                 if (c->mm == mm)
418                         goto assign_new_owner;
419         }
420 
421         /*
422          * Search through everything else, we should not get here often.
423          */
424         for_each_process(g) {
425                 if (g->flags & PF_KTHREAD)
426                         continue;
427                 for_each_thread(g, c) {
428                         if (c->mm == mm)
429                                 goto assign_new_owner;
430                         if (c->mm)
431                                 break;
432                 }
433         }
434         read_unlock(&tasklist_lock);
435         /*
436          * We found no owner yet mm_users > 1: this implies that we are
437          * most likely racing with swapoff (try_to_unuse()) or /proc or
438          * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
439          */
440         mm->owner = NULL;
441         return;
442 
443 assign_new_owner:
444         BUG_ON(c == p);
445         get_task_struct(c);
446         /*
447          * The task_lock protects c->mm from changing.
448          * We always want mm->owner->mm == mm
449          */
450         task_lock(c);
451         /*
452          * Delay read_unlock() till we have the task_lock()
453          * to ensure that c does not slip away underneath us
454          */
455         read_unlock(&tasklist_lock);
456         if (c->mm != mm) {
457                 task_unlock(c);
458                 put_task_struct(c);
459                 goto retry;
460         }
461         mm->owner = c;
462         task_unlock(c);
463         put_task_struct(c);
464 }
465 #endif /* CONFIG_MEMCG */
466 
467 /*
468  * Turn us into a lazy TLB process if we
469  * aren't already..
470  */
471 static void exit_mm(struct task_struct *tsk)
472 {
473         struct mm_struct *mm = tsk->mm;
474         struct core_state *core_state;
475 
476         mm_release(tsk, mm);
477         if (!mm)
478                 return;
479         sync_mm_rss(mm);
480         /*
481          * Serialize with any possible pending coredump.
482          * We must hold mmap_sem around checking core_state
483          * and clearing tsk->mm.  The core-inducing thread
484          * will increment ->nr_threads for each thread in the
485          * group with ->mm != NULL.
486          */
487         down_read(&mm->mmap_sem);
488         core_state = mm->core_state;
489         if (core_state) {
490                 struct core_thread self;
491 
492                 up_read(&mm->mmap_sem);
493 
494                 self.task = tsk;
495                 self.next = xchg(&core_state->dumper.next, &self);
496                 /*
497                  * Implies mb(), the result of xchg() must be visible
498                  * to core_state->dumper.
499                  */
500                 if (atomic_dec_and_test(&core_state->nr_threads))
501                         complete(&core_state->startup);
502 
503                 for (;;) {
504                         set_task_state(tsk, TASK_UNINTERRUPTIBLE);
505                         if (!self.task) /* see coredump_finish() */
506                                 break;
507                         freezable_schedule();
508                 }
509                 __set_task_state(tsk, TASK_RUNNING);
510                 down_read(&mm->mmap_sem);
511         }
512         atomic_inc(&mm->mm_count);
513         BUG_ON(mm != tsk->active_mm);
514         /* more a memory barrier than a real lock */
515         task_lock(tsk);
516         tsk->mm = NULL;
517         up_read(&mm->mmap_sem);
518         enter_lazy_tlb(mm, current);
519         task_unlock(tsk);
520         mm_update_next_owner(mm);
521         mmput(mm);
522         if (test_thread_flag(TIF_MEMDIE))
523                 exit_oom_victim();
524 }
525 
526 static struct task_struct *find_alive_thread(struct task_struct *p)
527 {
528         struct task_struct *t;
529 
530         for_each_thread(p, t) {
531                 if (!(t->flags & PF_EXITING))
532                         return t;
533         }
534         return NULL;
535 }
536 
537 static struct task_struct *find_child_reaper(struct task_struct *father)
538         __releases(&tasklist_lock)
539         __acquires(&tasklist_lock)
540 {
541         struct pid_namespace *pid_ns = task_active_pid_ns(father);
542         struct task_struct *reaper = pid_ns->child_reaper;
543 
544         if (likely(reaper != father))
545                 return reaper;
546 
547         reaper = find_alive_thread(father);
548         if (reaper) {
549                 pid_ns->child_reaper = reaper;
550                 return reaper;
551         }
552 
553         write_unlock_irq(&tasklist_lock);
554         if (unlikely(pid_ns == &init_pid_ns)) {
555                 panic("Attempted to kill init! exitcode=0x%08x\n",
556                         father->signal->group_exit_code ?: father->exit_code);
557         }
558         zap_pid_ns_processes(pid_ns);
559         write_lock_irq(&tasklist_lock);
560 
561         return father;
562 }
563 
564 /*
565  * When we die, we re-parent all our children, and try to:
566  * 1. give them to another thread in our thread group, if such a member exists
567  * 2. give it to the first ancestor process which prctl'd itself as a
568  *    child_subreaper for its children (like a service manager)
569  * 3. give it to the init process (PID 1) in our pid namespace
570  */
571 static struct task_struct *find_new_reaper(struct task_struct *father,
572                                            struct task_struct *child_reaper)
573 {
574         struct task_struct *thread, *reaper;
575 
576         thread = find_alive_thread(father);
577         if (thread)
578                 return thread;
579 
580         if (father->signal->has_child_subreaper) {
581                 /*
582                  * Find the first ->is_child_subreaper ancestor in our pid_ns.
583                  * We start from father to ensure we can not look into another
584                  * namespace, this is safe because all its threads are dead.
585                  */
586                 for (reaper = father;
587                      !same_thread_group(reaper, child_reaper);
588                      reaper = reaper->real_parent) {
589                         /* call_usermodehelper() descendants need this check */
590                         if (reaper == &init_task)
591                                 break;
592                         if (!reaper->signal->is_child_subreaper)
593                                 continue;
594                         thread = find_alive_thread(reaper);
595                         if (thread)
596                                 return thread;
597                 }
598         }
599 
600         return child_reaper;
601 }
602 
603 /*
604 * Any that need to be release_task'd are put on the @dead list.
605  */
606 static void reparent_leader(struct task_struct *father, struct task_struct *p,
607                                 struct list_head *dead)
608 {
609         if (unlikely(p->exit_state == EXIT_DEAD))
610                 return;
611 
612         /* We don't want people slaying init. */
613         p->exit_signal = SIGCHLD;
614 
615         /* If it has exited notify the new parent about this child's death. */
616         if (!p->ptrace &&
617             p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
618                 if (do_notify_parent(p, p->exit_signal)) {
619                         p->exit_state = EXIT_DEAD;
620                         list_add(&p->ptrace_entry, dead);
621                 }
622         }
623 
624         kill_orphaned_pgrp(p, father);
625 }
626 
627 /*
628  * This does two things:
629  *
630  * A.  Make init inherit all the child processes
631  * B.  Check to see if any process groups have become orphaned
632  *      as a result of our exiting, and if they have any stopped
633  *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
634  */
635 static void forget_original_parent(struct task_struct *father,
636                                         struct list_head *dead)
637 {
638         struct task_struct *p, *t, *reaper;
639 
640         if (unlikely(!list_empty(&father->ptraced)))
641                 exit_ptrace(father, dead);
642 
643         /* Can drop and reacquire tasklist_lock */
644         reaper = find_child_reaper(father);
645         if (list_empty(&father->children))
646                 return;
647 
648         reaper = find_new_reaper(father, reaper);
649         list_for_each_entry(p, &father->children, sibling) {
650                 for_each_thread(p, t) {
651                         t->real_parent = reaper;
652                         BUG_ON((!t->ptrace) != (t->parent == father));
653                         if (likely(!t->ptrace))
654                                 t->parent = t->real_parent;
655                         if (t->pdeath_signal)
656                                 group_send_sig_info(t->pdeath_signal,
657                                                     SEND_SIG_NOINFO, t);
658                 }
659                 /*
660                  * If this is a threaded reparent there is no need to
661                  * notify anyone anything has happened.
662                  */
663                 if (!same_thread_group(reaper, father))
664                         reparent_leader(father, p, dead);
665         }
666         list_splice_tail_init(&father->children, &reaper->children);
667 }
668 
669 /*
670  * Send signals to all our closest relatives so that they know
671  * to properly mourn us..
672  */
673 static void exit_notify(struct task_struct *tsk, int group_dead)
674 {
675         bool autoreap;
676         struct task_struct *p, *n;
677         LIST_HEAD(dead);
678 
679         write_lock_irq(&tasklist_lock);
680         forget_original_parent(tsk, &dead);
681 
682         if (group_dead)
683                 kill_orphaned_pgrp(tsk->group_leader, NULL);
684 
685         if (unlikely(tsk->ptrace)) {
686                 int sig = thread_group_leader(tsk) &&
687                                 thread_group_empty(tsk) &&
688                                 !ptrace_reparented(tsk) ?
689                         tsk->exit_signal : SIGCHLD;
690                 autoreap = do_notify_parent(tsk, sig);
691         } else if (thread_group_leader(tsk)) {
692                 autoreap = thread_group_empty(tsk) &&
693                         do_notify_parent(tsk, tsk->exit_signal);
694         } else {
695                 autoreap = true;
696         }
697 
698         tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
699         if (tsk->exit_state == EXIT_DEAD)
700                 list_add(&tsk->ptrace_entry, &dead);
701 
702         /* mt-exec, de_thread() is waiting for group leader */
703         if (unlikely(tsk->signal->notify_count < 0))
704                 wake_up_process(tsk->signal->group_exit_task);
705         write_unlock_irq(&tasklist_lock);
706 
707         list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
708                 list_del_init(&p->ptrace_entry);
709                 release_task(p);
710         }
711 }
712 
713 #ifdef CONFIG_DEBUG_STACK_USAGE
714 static void check_stack_usage(void)
715 {
716         static DEFINE_SPINLOCK(low_water_lock);
717         static int lowest_to_date = THREAD_SIZE;
718         unsigned long free;
719 
720         free = stack_not_used(current);
721 
722         if (free >= lowest_to_date)
723                 return;
724 
725         spin_lock(&low_water_lock);
726         if (free < lowest_to_date) {
727                 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
728                         current->comm, task_pid_nr(current), free);
729                 lowest_to_date = free;
730         }
731         spin_unlock(&low_water_lock);
732 }
733 #else
734 static inline void check_stack_usage(void) {}
735 #endif
736 
737 void __noreturn do_exit(long code)
738 {
739         struct task_struct *tsk = current;
740         int group_dead;
741         TASKS_RCU(int tasks_rcu_i);
742 
743         profile_task_exit(tsk);
744         kcov_task_exit(tsk);
745 
746         WARN_ON(blk_needs_flush_plug(tsk));
747 
748         if (unlikely(in_interrupt()))
749                 panic("Aiee, killing interrupt handler!");
750         if (unlikely(!tsk->pid))
751                 panic("Attempted to kill the idle task!");
752 
753         /*
754          * If do_exit is called because this processes oopsed, it's possible
755          * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
756          * continuing. Amongst other possible reasons, this is to prevent
757          * mm_release()->clear_child_tid() from writing to a user-controlled
758          * kernel address.
759          */
760         set_fs(USER_DS);
761 
762         ptrace_event(PTRACE_EVENT_EXIT, code);
763 
764         validate_creds_for_do_exit(tsk);
765 
766         /*
767          * We're taking recursive faults here in do_exit. Safest is to just
768          * leave this task alone and wait for reboot.
769          */
770         if (unlikely(tsk->flags & PF_EXITING)) {
771                 pr_alert("Fixing recursive fault but reboot is needed!\n");
772                 /*
773                  * We can do this unlocked here. The futex code uses
774                  * this flag just to verify whether the pi state
775                  * cleanup has been done or not. In the worst case it
776                  * loops once more. We pretend that the cleanup was
777                  * done as there is no way to return. Either the
778                  * OWNER_DIED bit is set by now or we push the blocked
779                  * task into the wait for ever nirwana as well.
780                  */
781                 tsk->flags |= PF_EXITPIDONE;
782                 set_current_state(TASK_UNINTERRUPTIBLE);
783                 schedule();
784         }
785 
786         exit_signals(tsk);  /* sets PF_EXITING */
787         /*
788          * Ensure that all new tsk->pi_lock acquisitions must observe
789          * PF_EXITING. Serializes against futex.c:attach_to_pi_owner().
790          */
791         smp_mb();
792         /*
793          * Ensure that we must observe the pi_state in exit_mm() ->
794          * mm_release() -> exit_pi_state_list().
795          */
796         raw_spin_unlock_wait(&tsk->pi_lock);
797 
798         if (unlikely(in_atomic())) {
799                 pr_info("note: %s[%d] exited with preempt_count %d\n",
800                         current->comm, task_pid_nr(current),
801                         preempt_count());
802                 preempt_count_set(PREEMPT_ENABLED);
803         }
804 
805         /* sync mm's RSS info before statistics gathering */
806         if (tsk->mm)
807                 sync_mm_rss(tsk->mm);
808         acct_update_integrals(tsk);
809         group_dead = atomic_dec_and_test(&tsk->signal->live);
810         if (group_dead) {
811 #ifdef CONFIG_POSIX_TIMERS
812                 hrtimer_cancel(&tsk->signal->real_timer);
813                 exit_itimers(tsk->signal);
814 #endif
815                 if (tsk->mm)
816                         setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
817         }
818         acct_collect(code, group_dead);
819         if (group_dead)
820                 tty_audit_exit();
821         audit_free(tsk);
822 
823         tsk->exit_code = code;
824         taskstats_exit(tsk, group_dead);
825 
826         exit_mm(tsk);
827 
828         if (group_dead)
829                 acct_process();
830         trace_sched_process_exit(tsk);
831 
832         exit_sem(tsk);
833         exit_shm(tsk);
834         exit_files(tsk);
835         exit_fs(tsk);
836         if (group_dead)
837                 disassociate_ctty(1);
838         exit_task_namespaces(tsk);
839         exit_task_work(tsk);
840         exit_thread(tsk);
841 
842         /*
843          * Flush inherited counters to the parent - before the parent
844          * gets woken up by child-exit notifications.
845          *
846          * because of cgroup mode, must be called before cgroup_exit()
847          */
848         perf_event_exit_task(tsk);
849 
850         sched_autogroup_exit_task(tsk);
851         cgroup_exit(tsk);
852 
853         /*
854          * FIXME: do that only when needed, using sched_exit tracepoint
855          */
856         flush_ptrace_hw_breakpoint(tsk);
857 
858         TASKS_RCU(preempt_disable());
859         TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
860         TASKS_RCU(preempt_enable());
861         exit_notify(tsk, group_dead);
862         proc_exit_connector(tsk);
863         mpol_put_task_policy(tsk);
864 #ifdef CONFIG_FUTEX
865         if (unlikely(current->pi_state_cache))
866                 kfree(current->pi_state_cache);
867 #endif
868         /*
869          * Make sure we are holding no locks:
870          */
871         debug_check_no_locks_held();
872         /*
873          * We can do this unlocked here. The futex code uses this flag
874          * just to verify whether the pi state cleanup has been done
875          * or not. In the worst case it loops once more.
876          */
877         tsk->flags |= PF_EXITPIDONE;
878 
879         if (tsk->io_context)
880                 exit_io_context(tsk);
881 
882         if (tsk->splice_pipe)
883                 free_pipe_info(tsk->splice_pipe);
884 
885         if (tsk->task_frag.page)
886                 put_page(tsk->task_frag.page);
887 
888         validate_creds_for_do_exit(tsk);
889 
890         check_stack_usage();
891         preempt_disable();
892         if (tsk->nr_dirtied)
893                 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
894         exit_rcu();
895         TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i));
896 
897         do_task_dead();
898 }
899 EXPORT_SYMBOL_GPL(do_exit);
900 
901 void complete_and_exit(struct completion *comp, long code)
902 {
903         if (comp)
904                 complete(comp);
905 
906         do_exit(code);
907 }
908 EXPORT_SYMBOL(complete_and_exit);
909 
910 SYSCALL_DEFINE1(exit, int, error_code)
911 {
912         do_exit((error_code&0xff)<<8);
913 }
914 
915 /*
916  * Take down every thread in the group.  This is called by fatal signals
917  * as well as by sys_exit_group (below).
918  */
919 void
920 do_group_exit(int exit_code)
921 {
922         struct signal_struct *sig = current->signal;
923 
924         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
925 
926         if (signal_group_exit(sig))
927                 exit_code = sig->group_exit_code;
928         else if (!thread_group_empty(current)) {
929                 struct sighand_struct *const sighand = current->sighand;
930 
931                 spin_lock_irq(&sighand->siglock);
932                 if (signal_group_exit(sig))
933                         /* Another thread got here before we took the lock.  */
934                         exit_code = sig->group_exit_code;
935                 else {
936                         sig->group_exit_code = exit_code;
937                         sig->flags = SIGNAL_GROUP_EXIT;
938                         zap_other_threads(current);
939                 }
940                 spin_unlock_irq(&sighand->siglock);
941         }
942 
943         do_exit(exit_code);
944         /* NOTREACHED */
945 }
946 
947 /*
948  * this kills every thread in the thread group. Note that any externally
949  * wait4()-ing process will get the correct exit code - even if this
950  * thread is not the thread group leader.
951  */
952 SYSCALL_DEFINE1(exit_group, int, error_code)
953 {
954         do_group_exit((error_code & 0xff) << 8);
955         /* NOTREACHED */
956         return 0;
957 }
958 
959 struct wait_opts {
960         enum pid_type           wo_type;
961         int                     wo_flags;
962         struct pid              *wo_pid;
963 
964         struct siginfo __user   *wo_info;
965         int __user              *wo_stat;
966         struct rusage __user    *wo_rusage;
967 
968         wait_queue_t            child_wait;
969         int                     notask_error;
970 };
971 
972 static inline
973 struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
974 {
975         if (type != PIDTYPE_PID)
976                 task = task->group_leader;
977         return task->pids[type].pid;
978 }
979 
980 static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
981 {
982         return  wo->wo_type == PIDTYPE_MAX ||
983                 task_pid_type(p, wo->wo_type) == wo->wo_pid;
984 }
985 
986 static int
987 eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
988 {
989         if (!eligible_pid(wo, p))
990                 return 0;
991 
992         /*
993          * Wait for all children (clone and not) if __WALL is set or
994          * if it is traced by us.
995          */
996         if (ptrace || (wo->wo_flags & __WALL))
997                 return 1;
998 
999         /*
1000          * Otherwise, wait for clone children *only* if __WCLONE is set;
1001          * otherwise, wait for non-clone children *only*.
1002          *
1003          * Note: a "clone" child here is one that reports to its parent
1004          * using a signal other than SIGCHLD, or a non-leader thread which
1005          * we can only see if it is traced by us.
1006          */
1007         if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1008                 return 0;
1009 
1010         return 1;
1011 }
1012 
1013 static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
1014                                 pid_t pid, uid_t uid, int why, int status)
1015 {
1016         struct siginfo __user *infop;
1017         int retval = wo->wo_rusage
1018                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1019 
1020         put_task_struct(p);
1021         infop = wo->wo_info;
1022         if (infop) {
1023                 if (!retval)
1024                         retval = put_user(SIGCHLD, &infop->si_signo);
1025                 if (!retval)
1026                         retval = put_user(0, &infop->si_errno);
1027                 if (!retval)
1028                         retval = put_user((short)why, &infop->si_code);
1029                 if (!retval)
1030                         retval = put_user(pid, &infop->si_pid);
1031                 if (!retval)
1032                         retval = put_user(uid, &infop->si_uid);
1033                 if (!retval)
1034                         retval = put_user(status, &infop->si_status);
1035         }
1036         if (!retval)
1037                 retval = pid;
1038         return retval;
1039 }
1040 
1041 /*
1042  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1043  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1044  * the lock and this task is uninteresting.  If we return nonzero, we have
1045  * released the lock and the system call should return.
1046  */
1047 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1048 {
1049         int state, retval, status;
1050         pid_t pid = task_pid_vnr(p);
1051         uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1052         struct siginfo __user *infop;
1053 
1054         if (!likely(wo->wo_flags & WEXITED))
1055                 return 0;
1056 
1057         if (unlikely(wo->wo_flags & WNOWAIT)) {
1058                 int exit_code = p->exit_code;
1059                 int why;
1060 
1061                 get_task_struct(p);
1062                 read_unlock(&tasklist_lock);
1063                 sched_annotate_sleep();
1064 
1065                 if ((exit_code & 0x7f) == 0) {
1066                         why = CLD_EXITED;
1067                         status = exit_code >> 8;
1068                 } else {
1069                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1070                         status = exit_code & 0x7f;
1071                 }
1072                 return wait_noreap_copyout(wo, p, pid, uid, why, status);
1073         }
1074         /*
1075          * Move the task's state to DEAD/TRACE, only one thread can do this.
1076          */
1077         state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1078                 EXIT_TRACE : EXIT_DEAD;
1079         if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1080                 return 0;
1081         /*
1082          * We own this thread, nobody else can reap it.
1083          */
1084         read_unlock(&tasklist_lock);
1085         sched_annotate_sleep();
1086 
1087         /*
1088          * Check thread_group_leader() to exclude the traced sub-threads.
1089          */
1090         if (state == EXIT_DEAD && thread_group_leader(p)) {
1091                 struct signal_struct *sig = p->signal;
1092                 struct signal_struct *psig = current->signal;
1093                 unsigned long maxrss;
1094                 cputime_t tgutime, tgstime;
1095 
1096                 /*
1097                  * The resource counters for the group leader are in its
1098                  * own task_struct.  Those for dead threads in the group
1099                  * are in its signal_struct, as are those for the child
1100                  * processes it has previously reaped.  All these
1101                  * accumulate in the parent's signal_struct c* fields.
1102                  *
1103                  * We don't bother to take a lock here to protect these
1104                  * p->signal fields because the whole thread group is dead
1105                  * and nobody can change them.
1106                  *
1107                  * psig->stats_lock also protects us from our sub-theads
1108                  * which can reap other children at the same time. Until
1109                  * we change k_getrusage()-like users to rely on this lock
1110                  * we have to take ->siglock as well.
1111                  *
1112                  * We use thread_group_cputime_adjusted() to get times for
1113                  * the thread group, which consolidates times for all threads
1114                  * in the group including the group leader.
1115                  */
1116                 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1117                 spin_lock_irq(&current->sighand->siglock);
1118                 write_seqlock(&psig->stats_lock);
1119                 psig->cutime += tgutime + sig->cutime;
1120                 psig->cstime += tgstime + sig->cstime;
1121                 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1122                 psig->cmin_flt +=
1123                         p->min_flt + sig->min_flt + sig->cmin_flt;
1124                 psig->cmaj_flt +=
1125                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1126                 psig->cnvcsw +=
1127                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1128                 psig->cnivcsw +=
1129                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1130                 psig->cinblock +=
1131                         task_io_get_inblock(p) +
1132                         sig->inblock + sig->cinblock;
1133                 psig->coublock +=
1134                         task_io_get_oublock(p) +
1135                         sig->oublock + sig->coublock;
1136                 maxrss = max(sig->maxrss, sig->cmaxrss);
1137                 if (psig->cmaxrss < maxrss)
1138                         psig->cmaxrss = maxrss;
1139                 task_io_accounting_add(&psig->ioac, &p->ioac);
1140                 task_io_accounting_add(&psig->ioac, &sig->ioac);
1141                 write_sequnlock(&psig->stats_lock);
1142                 spin_unlock_irq(&current->sighand->siglock);
1143         }
1144 
1145         retval = wo->wo_rusage
1146                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1147         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1148                 ? p->signal->group_exit_code : p->exit_code;
1149         if (!retval && wo->wo_stat)
1150                 retval = put_user(status, wo->wo_stat);
1151 
1152         infop = wo->wo_info;
1153         if (!retval && infop)
1154                 retval = put_user(SIGCHLD, &infop->si_signo);
1155         if (!retval && infop)
1156                 retval = put_user(0, &infop->si_errno);
1157         if (!retval && infop) {
1158                 int why;
1159 
1160                 if ((status & 0x7f) == 0) {
1161                         why = CLD_EXITED;
1162                         status >>= 8;
1163                 } else {
1164                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1165                         status &= 0x7f;
1166                 }
1167                 retval = put_user((short)why, &infop->si_code);
1168                 if (!retval)
1169                         retval = put_user(status, &infop->si_status);
1170         }
1171         if (!retval && infop)
1172                 retval = put_user(pid, &infop->si_pid);
1173         if (!retval && infop)
1174                 retval = put_user(uid, &infop->si_uid);
1175         if (!retval)
1176                 retval = pid;
1177 
1178         if (state == EXIT_TRACE) {
1179                 write_lock_irq(&tasklist_lock);
1180                 /* We dropped tasklist, ptracer could die and untrace */
1181                 ptrace_unlink(p);
1182 
1183                 /* If parent wants a zombie, don't release it now */
1184                 state = EXIT_ZOMBIE;
1185                 if (do_notify_parent(p, p->exit_signal))
1186                         state = EXIT_DEAD;
1187                 p->exit_state = state;
1188                 write_unlock_irq(&tasklist_lock);
1189         }
1190         if (state == EXIT_DEAD)
1191                 release_task(p);
1192 
1193         return retval;
1194 }
1195 
1196 static int *task_stopped_code(struct task_struct *p, bool ptrace)
1197 {
1198         if (ptrace) {
1199                 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1200                         return &p->exit_code;
1201         } else {
1202                 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1203                         return &p->signal->group_exit_code;
1204         }
1205         return NULL;
1206 }
1207 
1208 /**
1209  * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1210  * @wo: wait options
1211  * @ptrace: is the wait for ptrace
1212  * @p: task to wait for
1213  *
1214  * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1215  *
1216  * CONTEXT:
1217  * read_lock(&tasklist_lock), which is released if return value is
1218  * non-zero.  Also, grabs and releases @p->sighand->siglock.
1219  *
1220  * RETURNS:
1221  * 0 if wait condition didn't exist and search for other wait conditions
1222  * should continue.  Non-zero return, -errno on failure and @p's pid on
1223  * success, implies that tasklist_lock is released and wait condition
1224  * search should terminate.
1225  */
1226 static int wait_task_stopped(struct wait_opts *wo,
1227                                 int ptrace, struct task_struct *p)
1228 {
1229         struct siginfo __user *infop;
1230         int retval, exit_code, *p_code, why;
1231         uid_t uid = 0; /* unneeded, required by compiler */
1232         pid_t pid;
1233 
1234         /*
1235          * Traditionally we see ptrace'd stopped tasks regardless of options.
1236          */
1237         if (!ptrace && !(wo->wo_flags & WUNTRACED))
1238                 return 0;
1239 
1240         if (!task_stopped_code(p, ptrace))
1241                 return 0;
1242 
1243         exit_code = 0;
1244         spin_lock_irq(&p->sighand->siglock);
1245 
1246         p_code = task_stopped_code(p, ptrace);
1247         if (unlikely(!p_code))
1248                 goto unlock_sig;
1249 
1250         exit_code = *p_code;
1251         if (!exit_code)
1252                 goto unlock_sig;
1253 
1254         if (!unlikely(wo->wo_flags & WNOWAIT))
1255                 *p_code = 0;
1256 
1257         uid = from_kuid_munged(current_user_ns(), task_uid(p));
1258 unlock_sig:
1259         spin_unlock_irq(&p->sighand->siglock);
1260         if (!exit_code)
1261                 return 0;
1262 
1263         /*
1264          * Now we are pretty sure this task is interesting.
1265          * Make sure it doesn't get reaped out from under us while we
1266          * give up the lock and then examine it below.  We don't want to
1267          * keep holding onto the tasklist_lock while we call getrusage and
1268          * possibly take page faults for user memory.
1269          */
1270         get_task_struct(p);
1271         pid = task_pid_vnr(p);
1272         why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1273         read_unlock(&tasklist_lock);
1274         sched_annotate_sleep();
1275 
1276         if (unlikely(wo->wo_flags & WNOWAIT))
1277                 return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1278 
1279         retval = wo->wo_rusage
1280                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1281         if (!retval && wo->wo_stat)
1282                 retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1283 
1284         infop = wo->wo_info;
1285         if (!retval && infop)
1286                 retval = put_user(SIGCHLD, &infop->si_signo);
1287         if (!retval && infop)
1288                 retval = put_user(0, &infop->si_errno);
1289         if (!retval && infop)
1290                 retval = put_user((short)why, &infop->si_code);
1291         if (!retval && infop)
1292                 retval = put_user(exit_code, &infop->si_status);
1293         if (!retval && infop)
1294                 retval = put_user(pid, &infop->si_pid);
1295         if (!retval && infop)
1296                 retval = put_user(uid, &infop->si_uid);
1297         if (!retval)
1298                 retval = pid;
1299         put_task_struct(p);
1300 
1301         BUG_ON(!retval);
1302         return retval;
1303 }
1304 
1305 /*
1306  * Handle do_wait work for one task in a live, non-stopped state.
1307  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1308  * the lock and this task is uninteresting.  If we return nonzero, we have
1309  * released the lock and the system call should return.
1310  */
1311 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1312 {
1313         int retval;
1314         pid_t pid;
1315         uid_t uid;
1316 
1317         if (!unlikely(wo->wo_flags & WCONTINUED))
1318                 return 0;
1319 
1320         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1321                 return 0;
1322 
1323         spin_lock_irq(&p->sighand->siglock);
1324         /* Re-check with the lock held.  */
1325         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1326                 spin_unlock_irq(&p->sighand->siglock);
1327                 return 0;
1328         }
1329         if (!unlikely(wo->wo_flags & WNOWAIT))
1330                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1331         uid = from_kuid_munged(current_user_ns(), task_uid(p));
1332         spin_unlock_irq(&p->sighand->siglock);
1333 
1334         pid = task_pid_vnr(p);
1335         get_task_struct(p);
1336         read_unlock(&tasklist_lock);
1337         sched_annotate_sleep();
1338 
1339         if (!wo->wo_info) {
1340                 retval = wo->wo_rusage
1341                         ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1342                 put_task_struct(p);
1343                 if (!retval && wo->wo_stat)
1344                         retval = put_user(0xffff, wo->wo_stat);
1345                 if (!retval)
1346                         retval = pid;
1347         } else {
1348                 retval = wait_noreap_copyout(wo, p, pid, uid,
1349                                              CLD_CONTINUED, SIGCONT);
1350                 BUG_ON(retval == 0);
1351         }
1352 
1353         return retval;
1354 }
1355 
1356 /*
1357  * Consider @p for a wait by @parent.
1358  *
1359  * -ECHILD should be in ->notask_error before the first call.
1360  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1361  * Returns zero if the search for a child should continue;
1362  * then ->notask_error is 0 if @p is an eligible child,
1363  * or another error from security_task_wait(), or still -ECHILD.
1364  */
1365 static int wait_consider_task(struct wait_opts *wo, int ptrace,
1366                                 struct task_struct *p)
1367 {
1368         /*
1369          * We can race with wait_task_zombie() from another thread.
1370          * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1371          * can't confuse the checks below.
1372          */
1373         int exit_state = ACCESS_ONCE(p->exit_state);
1374         int ret;
1375 
1376         if (unlikely(exit_state == EXIT_DEAD))
1377                 return 0;
1378 
1379         ret = eligible_child(wo, ptrace, p);
1380         if (!ret)
1381                 return ret;
1382 
1383         ret = security_task_wait(p);
1384         if (unlikely(ret < 0)) {
1385                 /*
1386                  * If we have not yet seen any eligible child,
1387                  * then let this error code replace -ECHILD.
1388                  * A permission error will give the user a clue
1389                  * to look for security policy problems, rather
1390                  * than for mysterious wait bugs.
1391                  */
1392                 if (wo->notask_error)
1393                         wo->notask_error = ret;
1394                 return 0;
1395         }
1396 
1397         if (unlikely(exit_state == EXIT_TRACE)) {
1398                 /*
1399                  * ptrace == 0 means we are the natural parent. In this case
1400                  * we should clear notask_error, debugger will notify us.
1401                  */
1402                 if (likely(!ptrace))
1403                         wo->notask_error = 0;
1404                 return 0;
1405         }
1406 
1407         if (likely(!ptrace) && unlikely(p->ptrace)) {
1408                 /*
1409                  * If it is traced by its real parent's group, just pretend
1410                  * the caller is ptrace_do_wait() and reap this child if it
1411                  * is zombie.
1412                  *
1413                  * This also hides group stop state from real parent; otherwise
1414                  * a single stop can be reported twice as group and ptrace stop.
1415                  * If a ptracer wants to distinguish these two events for its
1416                  * own children it should create a separate process which takes
1417                  * the role of real parent.
1418                  */
1419                 if (!ptrace_reparented(p))
1420                         ptrace = 1;
1421         }
1422 
1423         /* slay zombie? */
1424         if (exit_state == EXIT_ZOMBIE) {
1425                 /* we don't reap group leaders with subthreads */
1426                 if (!delay_group_leader(p)) {
1427                         /*
1428                          * A zombie ptracee is only visible to its ptracer.
1429                          * Notification and reaping will be cascaded to the
1430                          * real parent when the ptracer detaches.
1431                          */
1432                         if (unlikely(ptrace) || likely(!p->ptrace))
1433                                 return wait_task_zombie(wo, p);
1434                 }
1435 
1436                 /*
1437                  * Allow access to stopped/continued state via zombie by
1438                  * falling through.  Clearing of notask_error is complex.
1439                  *
1440                  * When !@ptrace:
1441                  *
1442                  * If WEXITED is set, notask_error should naturally be
1443                  * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1444                  * so, if there are live subthreads, there are events to
1445                  * wait for.  If all subthreads are dead, it's still safe
1446                  * to clear - this function will be called again in finite
1447                  * amount time once all the subthreads are released and
1448                  * will then return without clearing.
1449                  *
1450                  * When @ptrace:
1451                  *
1452                  * Stopped state is per-task and thus can't change once the
1453                  * target task dies.  Only continued and exited can happen.
1454                  * Clear notask_error if WCONTINUED | WEXITED.
1455                  */
1456                 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1457                         wo->notask_error = 0;
1458         } else {
1459                 /*
1460                  * @p is alive and it's gonna stop, continue or exit, so
1461                  * there always is something to wait for.
1462                  */
1463                 wo->notask_error = 0;
1464         }
1465 
1466         /*
1467          * Wait for stopped.  Depending on @ptrace, different stopped state
1468          * is used and the two don't interact with each other.
1469          */
1470         ret = wait_task_stopped(wo, ptrace, p);
1471         if (ret)
1472                 return ret;
1473 
1474         /*
1475          * Wait for continued.  There's only one continued state and the
1476          * ptracer can consume it which can confuse the real parent.  Don't
1477          * use WCONTINUED from ptracer.  You don't need or want it.
1478          */
1479         return wait_task_continued(wo, p);
1480 }
1481 
1482 /*
1483  * Do the work of do_wait() for one thread in the group, @tsk.
1484  *
1485  * -ECHILD should be in ->notask_error before the first call.
1486  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1487  * Returns zero if the search for a child should continue; then
1488  * ->notask_error is 0 if there were any eligible children,
1489  * or another error from security_task_wait(), or still -ECHILD.
1490  */
1491 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1492 {
1493         struct task_struct *p;
1494 
1495         list_for_each_entry(p, &tsk->children, sibling) {
1496                 int ret = wait_consider_task(wo, 0, p);
1497 
1498                 if (ret)
1499                         return ret;
1500         }
1501 
1502         return 0;
1503 }
1504 
1505 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1506 {
1507         struct task_struct *p;
1508 
1509         list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1510                 int ret = wait_consider_task(wo, 1, p);
1511 
1512                 if (ret)
1513                         return ret;
1514         }
1515 
1516         return 0;
1517 }
1518 
1519 static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1520                                 int sync, void *key)
1521 {
1522         struct wait_opts *wo = container_of(wait, struct wait_opts,
1523                                                 child_wait);
1524         struct task_struct *p = key;
1525 
1526         if (!eligible_pid(wo, p))
1527                 return 0;
1528 
1529         if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1530                 return 0;
1531 
1532         return default_wake_function(wait, mode, sync, key);
1533 }
1534 
1535 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1536 {
1537         __wake_up_sync_key(&parent->signal->wait_chldexit,
1538                                 TASK_INTERRUPTIBLE, 1, p);
1539 }
1540 
1541 static long do_wait(struct wait_opts *wo)
1542 {
1543         struct task_struct *tsk;
1544         int retval;
1545 
1546         trace_sched_process_wait(wo->wo_pid);
1547 
1548         init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1549         wo->child_wait.private = current;
1550         add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1551 repeat:
1552         /*
1553          * If there is nothing that can match our criteria, just get out.
1554          * We will clear ->notask_error to zero if we see any child that
1555          * might later match our criteria, even if we are not able to reap
1556          * it yet.
1557          */
1558         wo->notask_error = -ECHILD;
1559         if ((wo->wo_type < PIDTYPE_MAX) &&
1560            (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1561                 goto notask;
1562 
1563         set_current_state(TASK_INTERRUPTIBLE);
1564         read_lock(&tasklist_lock);
1565         tsk = current;
1566         do {
1567                 retval = do_wait_thread(wo, tsk);
1568                 if (retval)
1569                         goto end;
1570 
1571                 retval = ptrace_do_wait(wo, tsk);
1572                 if (retval)
1573                         goto end;
1574 
1575                 if (wo->wo_flags & __WNOTHREAD)
1576                         break;
1577         } while_each_thread(current, tsk);
1578         read_unlock(&tasklist_lock);
1579 
1580 notask:
1581         retval = wo->notask_error;
1582         if (!retval && !(wo->wo_flags & WNOHANG)) {
1583                 retval = -ERESTARTSYS;
1584                 if (!signal_pending(current)) {
1585                         schedule();
1586                         goto repeat;
1587                 }
1588         }
1589 end:
1590         __set_current_state(TASK_RUNNING);
1591         remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1592         return retval;
1593 }
1594 
1595 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1596                 infop, int, options, struct rusage __user *, ru)
1597 {
1598         struct wait_opts wo;
1599         struct pid *pid = NULL;
1600         enum pid_type type;
1601         long ret;
1602 
1603         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1604                         __WNOTHREAD|__WCLONE|__WALL))
1605                 return -EINVAL;
1606         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1607                 return -EINVAL;
1608 
1609         switch (which) {
1610         case P_ALL:
1611                 type = PIDTYPE_MAX;
1612                 break;
1613         case P_PID:
1614                 type = PIDTYPE_PID;
1615                 if (upid <= 0)
1616                         return -EINVAL;
1617                 break;
1618         case P_PGID:
1619                 type = PIDTYPE_PGID;
1620                 if (upid <= 0)
1621                         return -EINVAL;
1622                 break;
1623         default:
1624                 return -EINVAL;
1625         }
1626 
1627         if (type < PIDTYPE_MAX)
1628                 pid = find_get_pid(upid);
1629 
1630         wo.wo_type      = type;
1631         wo.wo_pid       = pid;
1632         wo.wo_flags     = options;
1633         wo.wo_info      = infop;
1634         wo.wo_stat      = NULL;
1635         wo.wo_rusage    = ru;
1636         ret = do_wait(&wo);
1637 
1638         if (ret > 0) {
1639                 ret = 0;
1640         } else if (infop) {
1641                 /*
1642                  * For a WNOHANG return, clear out all the fields
1643                  * we would set so the user can easily tell the
1644                  * difference.
1645                  */
1646                 if (!ret)
1647                         ret = put_user(0, &infop->si_signo);
1648                 if (!ret)
1649                         ret = put_user(0, &infop->si_errno);
1650                 if (!ret)
1651                         ret = put_user(0, &infop->si_code);
1652                 if (!ret)
1653                         ret = put_user(0, &infop->si_pid);
1654                 if (!ret)
1655                         ret = put_user(0, &infop->si_uid);
1656                 if (!ret)
1657                         ret = put_user(0, &infop->si_status);
1658         }
1659 
1660         put_pid(pid);
1661         return ret;
1662 }
1663 
1664 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1665                 int, options, struct rusage __user *, ru)
1666 {
1667         struct wait_opts wo;
1668         struct pid *pid = NULL;
1669         enum pid_type type;
1670         long ret;
1671 
1672         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1673                         __WNOTHREAD|__WCLONE|__WALL))
1674                 return -EINVAL;
1675 
1676         if (upid == -1)
1677                 type = PIDTYPE_MAX;
1678         else if (upid < 0) {
1679                 type = PIDTYPE_PGID;
1680                 pid = find_get_pid(-upid);
1681         } else if (upid == 0) {
1682                 type = PIDTYPE_PGID;
1683                 pid = get_task_pid(current, PIDTYPE_PGID);
1684         } else /* upid > 0 */ {
1685                 type = PIDTYPE_PID;
1686                 pid = find_get_pid(upid);
1687         }
1688 
1689         wo.wo_type      = type;
1690         wo.wo_pid       = pid;
1691         wo.wo_flags     = options | WEXITED;
1692         wo.wo_info      = NULL;
1693         wo.wo_stat      = stat_addr;
1694         wo.wo_rusage    = ru;
1695         ret = do_wait(&wo);
1696         put_pid(pid);
1697 
1698         return ret;
1699 }
1700 
1701 #ifdef __ARCH_WANT_SYS_WAITPID
1702 
1703 /*
1704  * sys_waitpid() remains for compatibility. waitpid() should be
1705  * implemented by calling sys_wait4() from libc.a.
1706  */
1707 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1708 {
1709         return sys_wait4(pid, stat_addr, options, NULL);
1710 }
1711 
1712 #endif
1713 

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