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TOMOYO Linux Cross Reference
Linux/kernel/exit.c

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  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 
 57 #include <asm/uaccess.h>
 58 #include <asm/unistd.h>
 59 #include <asm/pgtable.h>
 60 #include <asm/mmu_context.h>
 61 
 62 static void exit_mm(struct task_struct * tsk);
 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 }
 78 
 79 /*
 80  * This function expects the tasklist_lock write-locked.
 81  */
 82 static void __exit_signal(struct task_struct *tsk)
 83 {
 84         struct signal_struct *sig = tsk->signal;
 85         bool group_dead = thread_group_leader(tsk);
 86         struct sighand_struct *sighand;
 87         struct tty_struct *uninitialized_var(tty);
 88         cputime_t utime, stime;
 89 
 90         sighand = rcu_dereference_check(tsk->sighand,
 91                                         lockdep_tasklist_lock_is_held());
 92         spin_lock(&sighand->siglock);
 93 
 94         posix_cpu_timers_exit(tsk);
 95         if (group_dead) {
 96                 posix_cpu_timers_exit_group(tsk);
 97                 tty = sig->tty;
 98                 sig->tty = NULL;
 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                 /*
109                  * If there is any task waiting for the group exit
110                  * then notify it:
111                  */
112                 if (sig->notify_count > 0 && !--sig->notify_count)
113                         wake_up_process(sig->group_exit_task);
114 
115                 if (tsk == sig->curr_target)
116                         sig->curr_target = next_thread(tsk);
117                 /*
118                  * Accumulate here the counters for all threads but the
119                  * group leader as they die, so they can be added into
120                  * the process-wide totals when those are taken.
121                  * The group leader stays around as a zombie as long
122                  * as there are other threads.  When it gets reaped,
123                  * the exit.c code will add its counts into these totals.
124                  * We won't ever get here for the group leader, since it
125                  * will have been the last reference on the signal_struct.
126                  */
127                 task_cputime(tsk, &utime, &stime);
128                 sig->utime += utime;
129                 sig->stime += stime;
130                 sig->gtime += task_gtime(tsk);
131                 sig->min_flt += tsk->min_flt;
132                 sig->maj_flt += tsk->maj_flt;
133                 sig->nvcsw += tsk->nvcsw;
134                 sig->nivcsw += tsk->nivcsw;
135                 sig->inblock += task_io_get_inblock(tsk);
136                 sig->oublock += task_io_get_oublock(tsk);
137                 task_io_accounting_add(&sig->ioac, &tsk->ioac);
138                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
139         }
140 
141         sig->nr_threads--;
142         __unhash_process(tsk, group_dead);
143 
144         /*
145          * Do this under ->siglock, we can race with another thread
146          * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
147          */
148         flush_sigqueue(&tsk->pending);
149         tsk->sighand = NULL;
150         spin_unlock(&sighand->siglock);
151 
152         __cleanup_sighand(sighand);
153         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
154         if (group_dead) {
155                 flush_sigqueue(&sig->shared_pending);
156                 tty_kref_put(tty);
157         }
158 }
159 
160 static void delayed_put_task_struct(struct rcu_head *rhp)
161 {
162         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
163 
164         perf_event_delayed_put(tsk);
165         trace_sched_process_free(tsk);
166         put_task_struct(tsk);
167 }
168 
169 
170 void release_task(struct task_struct * p)
171 {
172         struct task_struct *leader;
173         int zap_leader;
174 repeat:
175         /* don't need to get the RCU readlock here - the process is dead and
176          * can't be modifying its own credentials. But shut RCU-lockdep up */
177         rcu_read_lock();
178         atomic_dec(&__task_cred(p)->user->processes);
179         rcu_read_unlock();
180 
181         proc_flush_task(p);
182 
183         write_lock_irq(&tasklist_lock);
184         ptrace_release_task(p);
185         __exit_signal(p);
186 
187         /*
188          * If we are the last non-leader member of the thread
189          * group, and the leader is zombie, then notify the
190          * group leader's parent process. (if it wants notification.)
191          */
192         zap_leader = 0;
193         leader = p->group_leader;
194         if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
195                 /*
196                  * If we were the last child thread and the leader has
197                  * exited already, and the leader's parent ignores SIGCHLD,
198                  * then we are the one who should release the leader.
199                  */
200                 zap_leader = do_notify_parent(leader, leader->exit_signal);
201                 if (zap_leader)
202                         leader->exit_state = EXIT_DEAD;
203         }
204 
205         write_unlock_irq(&tasklist_lock);
206         release_thread(p);
207         call_rcu(&p->rcu, delayed_put_task_struct);
208 
209         p = leader;
210         if (unlikely(zap_leader))
211                 goto repeat;
212 }
213 
214 /*
215  * This checks not only the pgrp, but falls back on the pid if no
216  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
217  * without this...
218  *
219  * The caller must hold rcu lock or the tasklist lock.
220  */
221 struct pid *session_of_pgrp(struct pid *pgrp)
222 {
223         struct task_struct *p;
224         struct pid *sid = NULL;
225 
226         p = pid_task(pgrp, PIDTYPE_PGID);
227         if (p == NULL)
228                 p = pid_task(pgrp, PIDTYPE_PID);
229         if (p != NULL)
230                 sid = task_session(p);
231 
232         return sid;
233 }
234 
235 /*
236  * Determine if a process group is "orphaned", according to the POSIX
237  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
238  * by terminal-generated stop signals.  Newly orphaned process groups are
239  * to receive a SIGHUP and a SIGCONT.
240  *
241  * "I ask you, have you ever known what it is to be an orphan?"
242  */
243 static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
244 {
245         struct task_struct *p;
246 
247         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
248                 if ((p == ignored_task) ||
249                     (p->exit_state && thread_group_empty(p)) ||
250                     is_global_init(p->real_parent))
251                         continue;
252 
253                 if (task_pgrp(p->real_parent) != pgrp &&
254                     task_session(p->real_parent) == task_session(p))
255                         return 0;
256         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
257 
258         return 1;
259 }
260 
261 int is_current_pgrp_orphaned(void)
262 {
263         int retval;
264 
265         read_lock(&tasklist_lock);
266         retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
267         read_unlock(&tasklist_lock);
268 
269         return retval;
270 }
271 
272 static bool has_stopped_jobs(struct pid *pgrp)
273 {
274         struct task_struct *p;
275 
276         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
277                 if (p->signal->flags & SIGNAL_STOP_STOPPED)
278                         return true;
279         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
280 
281         return false;
282 }
283 
284 /*
285  * Check to see if any process groups have become orphaned as
286  * a result of our exiting, and if they have any stopped jobs,
287  * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
288  */
289 static void
290 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
291 {
292         struct pid *pgrp = task_pgrp(tsk);
293         struct task_struct *ignored_task = tsk;
294 
295         if (!parent)
296                  /* exit: our father is in a different pgrp than
297                   * we are and we were the only connection outside.
298                   */
299                 parent = tsk->real_parent;
300         else
301                 /* reparent: our child is in a different pgrp than
302                  * we are, and it was the only connection outside.
303                  */
304                 ignored_task = NULL;
305 
306         if (task_pgrp(parent) != pgrp &&
307             task_session(parent) == task_session(tsk) &&
308             will_become_orphaned_pgrp(pgrp, ignored_task) &&
309             has_stopped_jobs(pgrp)) {
310                 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
311                 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
312         }
313 }
314 
315 /*
316  * Let kernel threads use this to say that they allow a certain signal.
317  * Must not be used if kthread was cloned with CLONE_SIGHAND.
318  */
319 int allow_signal(int sig)
320 {
321         if (!valid_signal(sig) || sig < 1)
322                 return -EINVAL;
323 
324         spin_lock_irq(&current->sighand->siglock);
325         /* This is only needed for daemonize()'ed kthreads */
326         sigdelset(&current->blocked, sig);
327         /*
328          * Kernel threads handle their own signals. Let the signal code
329          * know it'll be handled, so that they don't get converted to
330          * SIGKILL or just silently dropped.
331          */
332         current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
333         recalc_sigpending();
334         spin_unlock_irq(&current->sighand->siglock);
335         return 0;
336 }
337 
338 EXPORT_SYMBOL(allow_signal);
339 
340 int disallow_signal(int sig)
341 {
342         if (!valid_signal(sig) || sig < 1)
343                 return -EINVAL;
344 
345         spin_lock_irq(&current->sighand->siglock);
346         current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
347         recalc_sigpending();
348         spin_unlock_irq(&current->sighand->siglock);
349         return 0;
350 }
351 
352 EXPORT_SYMBOL(disallow_signal);
353 
354 #ifdef CONFIG_MM_OWNER
355 /*
356  * A task is exiting.   If it owned this mm, find a new owner for the mm.
357  */
358 void mm_update_next_owner(struct mm_struct *mm)
359 {
360         struct task_struct *c, *g, *p = current;
361 
362 retry:
363         /*
364          * If the exiting or execing task is not the owner, it's
365          * someone else's problem.
366          */
367         if (mm->owner != p)
368                 return;
369         /*
370          * The current owner is exiting/execing and there are no other
371          * candidates.  Do not leave the mm pointing to a possibly
372          * freed task structure.
373          */
374         if (atomic_read(&mm->mm_users) <= 1) {
375                 mm->owner = NULL;
376                 return;
377         }
378 
379         read_lock(&tasklist_lock);
380         /*
381          * Search in the children
382          */
383         list_for_each_entry(c, &p->children, sibling) {
384                 if (c->mm == mm)
385                         goto assign_new_owner;
386         }
387 
388         /*
389          * Search in the siblings
390          */
391         list_for_each_entry(c, &p->real_parent->children, sibling) {
392                 if (c->mm == mm)
393                         goto assign_new_owner;
394         }
395 
396         /*
397          * Search through everything else. We should not get
398          * here often
399          */
400         do_each_thread(g, c) {
401                 if (c->mm == mm)
402                         goto assign_new_owner;
403         } while_each_thread(g, c);
404 
405         read_unlock(&tasklist_lock);
406         /*
407          * We found no owner yet mm_users > 1: this implies that we are
408          * most likely racing with swapoff (try_to_unuse()) or /proc or
409          * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
410          */
411         mm->owner = NULL;
412         return;
413 
414 assign_new_owner:
415         BUG_ON(c == p);
416         get_task_struct(c);
417         /*
418          * The task_lock protects c->mm from changing.
419          * We always want mm->owner->mm == mm
420          */
421         task_lock(c);
422         /*
423          * Delay read_unlock() till we have the task_lock()
424          * to ensure that c does not slip away underneath us
425          */
426         read_unlock(&tasklist_lock);
427         if (c->mm != mm) {
428                 task_unlock(c);
429                 put_task_struct(c);
430                 goto retry;
431         }
432         mm->owner = c;
433         task_unlock(c);
434         put_task_struct(c);
435 }
436 #endif /* CONFIG_MM_OWNER */
437 
438 /*
439  * Turn us into a lazy TLB process if we
440  * aren't already..
441  */
442 static void exit_mm(struct task_struct * tsk)
443 {
444         struct mm_struct *mm = tsk->mm;
445         struct core_state *core_state;
446 
447         mm_release(tsk, mm);
448         if (!mm)
449                 return;
450         sync_mm_rss(mm);
451         /*
452          * Serialize with any possible pending coredump.
453          * We must hold mmap_sem around checking core_state
454          * and clearing tsk->mm.  The core-inducing thread
455          * will increment ->nr_threads for each thread in the
456          * group with ->mm != NULL.
457          */
458         down_read(&mm->mmap_sem);
459         core_state = mm->core_state;
460         if (core_state) {
461                 struct core_thread self;
462                 up_read(&mm->mmap_sem);
463 
464                 self.task = tsk;
465                 self.next = xchg(&core_state->dumper.next, &self);
466                 /*
467                  * Implies mb(), the result of xchg() must be visible
468                  * to core_state->dumper.
469                  */
470                 if (atomic_dec_and_test(&core_state->nr_threads))
471                         complete(&core_state->startup);
472 
473                 for (;;) {
474                         set_task_state(tsk, TASK_UNINTERRUPTIBLE);
475                         if (!self.task) /* see coredump_finish() */
476                                 break;
477                         freezable_schedule();
478                 }
479                 __set_task_state(tsk, TASK_RUNNING);
480                 down_read(&mm->mmap_sem);
481         }
482         atomic_inc(&mm->mm_count);
483         BUG_ON(mm != tsk->active_mm);
484         /* more a memory barrier than a real lock */
485         task_lock(tsk);
486         tsk->mm = NULL;
487         up_read(&mm->mmap_sem);
488         enter_lazy_tlb(mm, current);
489         task_unlock(tsk);
490         mm_update_next_owner(mm);
491         mmput(mm);
492 }
493 
494 /*
495  * When we die, we re-parent all our children, and try to:
496  * 1. give them to another thread in our thread group, if such a member exists
497  * 2. give it to the first ancestor process which prctl'd itself as a
498  *    child_subreaper for its children (like a service manager)
499  * 3. give it to the init process (PID 1) in our pid namespace
500  */
501 static struct task_struct *find_new_reaper(struct task_struct *father)
502         __releases(&tasklist_lock)
503         __acquires(&tasklist_lock)
504 {
505         struct pid_namespace *pid_ns = task_active_pid_ns(father);
506         struct task_struct *thread;
507 
508         thread = father;
509         while_each_thread(father, thread) {
510                 if (thread->flags & PF_EXITING)
511                         continue;
512                 if (unlikely(pid_ns->child_reaper == father))
513                         pid_ns->child_reaper = thread;
514                 return thread;
515         }
516 
517         if (unlikely(pid_ns->child_reaper == father)) {
518                 write_unlock_irq(&tasklist_lock);
519                 if (unlikely(pid_ns == &init_pid_ns)) {
520                         panic("Attempted to kill init! exitcode=0x%08x\n",
521                                 father->signal->group_exit_code ?:
522                                         father->exit_code);
523                 }
524 
525                 zap_pid_ns_processes(pid_ns);
526                 write_lock_irq(&tasklist_lock);
527         } else if (father->signal->has_child_subreaper) {
528                 struct task_struct *reaper;
529 
530                 /*
531                  * Find the first ancestor marked as child_subreaper.
532                  * Note that the code below checks same_thread_group(reaper,
533                  * pid_ns->child_reaper).  This is what we need to DTRT in a
534                  * PID namespace. However we still need the check above, see
535                  * http://marc.info/?l=linux-kernel&m=131385460420380
536                  */
537                 for (reaper = father->real_parent;
538                      reaper != &init_task;
539                      reaper = reaper->real_parent) {
540                         if (same_thread_group(reaper, pid_ns->child_reaper))
541                                 break;
542                         if (!reaper->signal->is_child_subreaper)
543                                 continue;
544                         thread = reaper;
545                         do {
546                                 if (!(thread->flags & PF_EXITING))
547                                         return reaper;
548                         } while_each_thread(reaper, thread);
549                 }
550         }
551 
552         return pid_ns->child_reaper;
553 }
554 
555 /*
556 * Any that need to be release_task'd are put on the @dead list.
557  */
558 static void reparent_leader(struct task_struct *father, struct task_struct *p,
559                                 struct list_head *dead)
560 {
561         list_move_tail(&p->sibling, &p->real_parent->children);
562 
563         if (p->exit_state == EXIT_DEAD)
564                 return;
565         /*
566          * If this is a threaded reparent there is no need to
567          * notify anyone anything has happened.
568          */
569         if (same_thread_group(p->real_parent, father))
570                 return;
571 
572         /* We don't want people slaying init.  */
573         p->exit_signal = SIGCHLD;
574 
575         /* If it has exited notify the new parent about this child's death. */
576         if (!p->ptrace &&
577             p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
578                 if (do_notify_parent(p, p->exit_signal)) {
579                         p->exit_state = EXIT_DEAD;
580                         list_move_tail(&p->sibling, dead);
581                 }
582         }
583 
584         kill_orphaned_pgrp(p, father);
585 }
586 
587 static void forget_original_parent(struct task_struct *father)
588 {
589         struct task_struct *p, *n, *reaper;
590         LIST_HEAD(dead_children);
591 
592         write_lock_irq(&tasklist_lock);
593         /*
594          * Note that exit_ptrace() and find_new_reaper() might
595          * drop tasklist_lock and reacquire it.
596          */
597         exit_ptrace(father);
598         reaper = find_new_reaper(father);
599 
600         list_for_each_entry_safe(p, n, &father->children, sibling) {
601                 struct task_struct *t = p;
602                 do {
603                         t->real_parent = reaper;
604                         if (t->parent == father) {
605                                 BUG_ON(t->ptrace);
606                                 t->parent = t->real_parent;
607                         }
608                         if (t->pdeath_signal)
609                                 group_send_sig_info(t->pdeath_signal,
610                                                     SEND_SIG_NOINFO, t);
611                 } while_each_thread(p, t);
612                 reparent_leader(father, p, &dead_children);
613         }
614         write_unlock_irq(&tasklist_lock);
615 
616         BUG_ON(!list_empty(&father->children));
617 
618         list_for_each_entry_safe(p, n, &dead_children, sibling) {
619                 list_del_init(&p->sibling);
620                 release_task(p);
621         }
622 }
623 
624 /*
625  * Send signals to all our closest relatives so that they know
626  * to properly mourn us..
627  */
628 static void exit_notify(struct task_struct *tsk, int group_dead)
629 {
630         bool autoreap;
631 
632         /*
633          * This does two things:
634          *
635          * A.  Make init inherit all the child processes
636          * B.  Check to see if any process groups have become orphaned
637          *      as a result of our exiting, and if they have any stopped
638          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
639          */
640         forget_original_parent(tsk);
641 
642         write_lock_irq(&tasklist_lock);
643         if (group_dead)
644                 kill_orphaned_pgrp(tsk->group_leader, NULL);
645 
646         if (unlikely(tsk->ptrace)) {
647                 int sig = thread_group_leader(tsk) &&
648                                 thread_group_empty(tsk) &&
649                                 !ptrace_reparented(tsk) ?
650                         tsk->exit_signal : SIGCHLD;
651                 autoreap = do_notify_parent(tsk, sig);
652         } else if (thread_group_leader(tsk)) {
653                 autoreap = thread_group_empty(tsk) &&
654                         do_notify_parent(tsk, tsk->exit_signal);
655         } else {
656                 autoreap = true;
657         }
658 
659         tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
660 
661         /* mt-exec, de_thread() is waiting for group leader */
662         if (unlikely(tsk->signal->notify_count < 0))
663                 wake_up_process(tsk->signal->group_exit_task);
664         write_unlock_irq(&tasklist_lock);
665 
666         /* If the process is dead, release it - nobody will wait for it */
667         if (autoreap)
668                 release_task(tsk);
669 }
670 
671 #ifdef CONFIG_DEBUG_STACK_USAGE
672 static void check_stack_usage(void)
673 {
674         static DEFINE_SPINLOCK(low_water_lock);
675         static int lowest_to_date = THREAD_SIZE;
676         unsigned long free;
677 
678         free = stack_not_used(current);
679 
680         if (free >= lowest_to_date)
681                 return;
682 
683         spin_lock(&low_water_lock);
684         if (free < lowest_to_date) {
685                 printk(KERN_WARNING "%s (%d) used greatest stack depth: "
686                                 "%lu bytes left\n",
687                                 current->comm, task_pid_nr(current), free);
688                 lowest_to_date = free;
689         }
690         spin_unlock(&low_water_lock);
691 }
692 #else
693 static inline void check_stack_usage(void) {}
694 #endif
695 
696 void do_exit(long code)
697 {
698         struct task_struct *tsk = current;
699         int group_dead;
700 
701         profile_task_exit(tsk);
702 
703         WARN_ON(blk_needs_flush_plug(tsk));
704 
705         if (unlikely(in_interrupt()))
706                 panic("Aiee, killing interrupt handler!");
707         if (unlikely(!tsk->pid))
708                 panic("Attempted to kill the idle task!");
709 
710         /*
711          * If do_exit is called because this processes oopsed, it's possible
712          * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
713          * continuing. Amongst other possible reasons, this is to prevent
714          * mm_release()->clear_child_tid() from writing to a user-controlled
715          * kernel address.
716          */
717         set_fs(USER_DS);
718 
719         ptrace_event(PTRACE_EVENT_EXIT, code);
720 
721         validate_creds_for_do_exit(tsk);
722 
723         /*
724          * We're taking recursive faults here in do_exit. Safest is to just
725          * leave this task alone and wait for reboot.
726          */
727         if (unlikely(tsk->flags & PF_EXITING)) {
728                 printk(KERN_ALERT
729                         "Fixing recursive fault but reboot is needed!\n");
730                 /*
731                  * We can do this unlocked here. The futex code uses
732                  * this flag just to verify whether the pi state
733                  * cleanup has been done or not. In the worst case it
734                  * loops once more. We pretend that the cleanup was
735                  * done as there is no way to return. Either the
736                  * OWNER_DIED bit is set by now or we push the blocked
737                  * task into the wait for ever nirwana as well.
738                  */
739                 tsk->flags |= PF_EXITPIDONE;
740                 set_current_state(TASK_UNINTERRUPTIBLE);
741                 schedule();
742         }
743 
744         exit_signals(tsk);  /* sets PF_EXITING */
745         /*
746          * tsk->flags are checked in the futex code to protect against
747          * an exiting task cleaning up the robust pi futexes.
748          */
749         smp_mb();
750         raw_spin_unlock_wait(&tsk->pi_lock);
751 
752         if (unlikely(in_atomic()))
753                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
754                                 current->comm, task_pid_nr(current),
755                                 preempt_count());
756 
757         acct_update_integrals(tsk);
758         /* sync mm's RSS info before statistics gathering */
759         if (tsk->mm)
760                 sync_mm_rss(tsk->mm);
761         group_dead = atomic_dec_and_test(&tsk->signal->live);
762         if (group_dead) {
763                 hrtimer_cancel(&tsk->signal->real_timer);
764                 exit_itimers(tsk->signal);
765                 if (tsk->mm)
766                         setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
767         }
768         acct_collect(code, group_dead);
769         if (group_dead)
770                 tty_audit_exit();
771         audit_free(tsk);
772 
773         tsk->exit_code = code;
774         taskstats_exit(tsk, group_dead);
775 
776         exit_mm(tsk);
777 
778         if (group_dead)
779                 acct_process();
780         trace_sched_process_exit(tsk);
781 
782         exit_sem(tsk);
783         exit_shm(tsk);
784         exit_files(tsk);
785         exit_fs(tsk);
786         exit_task_namespaces(tsk);
787         exit_task_work(tsk);
788         check_stack_usage();
789         exit_thread();
790 
791         /*
792          * Flush inherited counters to the parent - before the parent
793          * gets woken up by child-exit notifications.
794          *
795          * because of cgroup mode, must be called before cgroup_exit()
796          */
797         perf_event_exit_task(tsk);
798 
799         cgroup_exit(tsk, 1);
800 
801         if (group_dead)
802                 disassociate_ctty(1);
803 
804         module_put(task_thread_info(tsk)->exec_domain->module);
805 
806         proc_exit_connector(tsk);
807 
808         /*
809          * FIXME: do that only when needed, using sched_exit tracepoint
810          */
811         flush_ptrace_hw_breakpoint(tsk);
812 
813         exit_notify(tsk, group_dead);
814 #ifdef CONFIG_NUMA
815         task_lock(tsk);
816         mpol_put(tsk->mempolicy);
817         tsk->mempolicy = NULL;
818         task_unlock(tsk);
819 #endif
820 #ifdef CONFIG_FUTEX
821         if (unlikely(current->pi_state_cache))
822                 kfree(current->pi_state_cache);
823 #endif
824         /*
825          * Make sure we are holding no locks:
826          */
827         debug_check_no_locks_held();
828         /*
829          * We can do this unlocked here. The futex code uses this flag
830          * just to verify whether the pi state cleanup has been done
831          * or not. In the worst case it loops once more.
832          */
833         tsk->flags |= PF_EXITPIDONE;
834 
835         if (tsk->io_context)
836                 exit_io_context(tsk);
837 
838         if (tsk->splice_pipe)
839                 free_pipe_info(tsk->splice_pipe);
840 
841         if (tsk->task_frag.page)
842                 put_page(tsk->task_frag.page);
843 
844         validate_creds_for_do_exit(tsk);
845 
846         preempt_disable();
847         if (tsk->nr_dirtied)
848                 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
849         exit_rcu();
850 
851         /*
852          * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
853          * when the following two conditions become true.
854          *   - There is race condition of mmap_sem (It is acquired by
855          *     exit_mm()), and
856          *   - SMI occurs before setting TASK_RUNINNG.
857          *     (or hypervisor of virtual machine switches to other guest)
858          *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
859          *
860          * To avoid it, we have to wait for releasing tsk->pi_lock which
861          * is held by try_to_wake_up()
862          */
863         smp_mb();
864         raw_spin_unlock_wait(&tsk->pi_lock);
865 
866         /* causes final put_task_struct in finish_task_switch(). */
867         tsk->state = TASK_DEAD;
868         tsk->flags |= PF_NOFREEZE;      /* tell freezer to ignore us */
869         schedule();
870         BUG();
871         /* Avoid "noreturn function does return".  */
872         for (;;)
873                 cpu_relax();    /* For when BUG is null */
874 }
875 
876 EXPORT_SYMBOL_GPL(do_exit);
877 
878 void complete_and_exit(struct completion *comp, long code)
879 {
880         if (comp)
881                 complete(comp);
882 
883         do_exit(code);
884 }
885 
886 EXPORT_SYMBOL(complete_and_exit);
887 
888 SYSCALL_DEFINE1(exit, int, error_code)
889 {
890         do_exit((error_code&0xff)<<8);
891 }
892 
893 /*
894  * Take down every thread in the group.  This is called by fatal signals
895  * as well as by sys_exit_group (below).
896  */
897 void
898 do_group_exit(int exit_code)
899 {
900         struct signal_struct *sig = current->signal;
901 
902         BUG_ON(exit_code & 0x80); /* core dumps don't get here */
903 
904         if (signal_group_exit(sig))
905                 exit_code = sig->group_exit_code;
906         else if (!thread_group_empty(current)) {
907                 struct sighand_struct *const sighand = current->sighand;
908                 spin_lock_irq(&sighand->siglock);
909                 if (signal_group_exit(sig))
910                         /* Another thread got here before we took the lock.  */
911                         exit_code = sig->group_exit_code;
912                 else {
913                         sig->group_exit_code = exit_code;
914                         sig->flags = SIGNAL_GROUP_EXIT;
915                         zap_other_threads(current);
916                 }
917                 spin_unlock_irq(&sighand->siglock);
918         }
919 
920         do_exit(exit_code);
921         /* NOTREACHED */
922 }
923 
924 /*
925  * this kills every thread in the thread group. Note that any externally
926  * wait4()-ing process will get the correct exit code - even if this
927  * thread is not the thread group leader.
928  */
929 SYSCALL_DEFINE1(exit_group, int, error_code)
930 {
931         do_group_exit((error_code & 0xff) << 8);
932         /* NOTREACHED */
933         return 0;
934 }
935 
936 struct wait_opts {
937         enum pid_type           wo_type;
938         int                     wo_flags;
939         struct pid              *wo_pid;
940 
941         struct siginfo __user   *wo_info;
942         int __user              *wo_stat;
943         struct rusage __user    *wo_rusage;
944 
945         wait_queue_t            child_wait;
946         int                     notask_error;
947 };
948 
949 static inline
950 struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
951 {
952         if (type != PIDTYPE_PID)
953                 task = task->group_leader;
954         return task->pids[type].pid;
955 }
956 
957 static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
958 {
959         return  wo->wo_type == PIDTYPE_MAX ||
960                 task_pid_type(p, wo->wo_type) == wo->wo_pid;
961 }
962 
963 static int eligible_child(struct wait_opts *wo, struct task_struct *p)
964 {
965         if (!eligible_pid(wo, p))
966                 return 0;
967         /* Wait for all children (clone and not) if __WALL is set;
968          * otherwise, wait for clone children *only* if __WCLONE is
969          * set; otherwise, wait for non-clone children *only*.  (Note:
970          * A "clone" child here is one that reports to its parent
971          * using a signal other than SIGCHLD.) */
972         if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
973             && !(wo->wo_flags & __WALL))
974                 return 0;
975 
976         return 1;
977 }
978 
979 static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
980                                 pid_t pid, uid_t uid, int why, int status)
981 {
982         struct siginfo __user *infop;
983         int retval = wo->wo_rusage
984                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
985 
986         put_task_struct(p);
987         infop = wo->wo_info;
988         if (infop) {
989                 if (!retval)
990                         retval = put_user(SIGCHLD, &infop->si_signo);
991                 if (!retval)
992                         retval = put_user(0, &infop->si_errno);
993                 if (!retval)
994                         retval = put_user((short)why, &infop->si_code);
995                 if (!retval)
996                         retval = put_user(pid, &infop->si_pid);
997                 if (!retval)
998                         retval = put_user(uid, &infop->si_uid);
999                 if (!retval)
1000                         retval = put_user(status, &infop->si_status);
1001         }
1002         if (!retval)
1003                 retval = pid;
1004         return retval;
1005 }
1006 
1007 /*
1008  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1009  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1010  * the lock and this task is uninteresting.  If we return nonzero, we have
1011  * released the lock and the system call should return.
1012  */
1013 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1014 {
1015         unsigned long state;
1016         int retval, status, traced;
1017         pid_t pid = task_pid_vnr(p);
1018         uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1019         struct siginfo __user *infop;
1020 
1021         if (!likely(wo->wo_flags & WEXITED))
1022                 return 0;
1023 
1024         if (unlikely(wo->wo_flags & WNOWAIT)) {
1025                 int exit_code = p->exit_code;
1026                 int why;
1027 
1028                 get_task_struct(p);
1029                 read_unlock(&tasklist_lock);
1030                 if ((exit_code & 0x7f) == 0) {
1031                         why = CLD_EXITED;
1032                         status = exit_code >> 8;
1033                 } else {
1034                         why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1035                         status = exit_code & 0x7f;
1036                 }
1037                 return wait_noreap_copyout(wo, p, pid, uid, why, status);
1038         }
1039 
1040         /*
1041          * Try to move the task's state to DEAD
1042          * only one thread is allowed to do this:
1043          */
1044         state = xchg(&p->exit_state, EXIT_DEAD);
1045         if (state != EXIT_ZOMBIE) {
1046                 BUG_ON(state != EXIT_DEAD);
1047                 return 0;
1048         }
1049 
1050         traced = ptrace_reparented(p);
1051         /*
1052          * It can be ptraced but not reparented, check
1053          * thread_group_leader() to filter out sub-threads.
1054          */
1055         if (likely(!traced) && thread_group_leader(p)) {
1056                 struct signal_struct *psig;
1057                 struct signal_struct *sig;
1058                 unsigned long maxrss;
1059                 cputime_t tgutime, tgstime;
1060 
1061                 /*
1062                  * The resource counters for the group leader are in its
1063                  * own task_struct.  Those for dead threads in the group
1064                  * are in its signal_struct, as are those for the child
1065                  * processes it has previously reaped.  All these
1066                  * accumulate in the parent's signal_struct c* fields.
1067                  *
1068                  * We don't bother to take a lock here to protect these
1069                  * p->signal fields, because they are only touched by
1070                  * __exit_signal, which runs with tasklist_lock
1071                  * write-locked anyway, and so is excluded here.  We do
1072                  * need to protect the access to parent->signal fields,
1073                  * as other threads in the parent group can be right
1074                  * here reaping other children at the same time.
1075                  *
1076                  * We use thread_group_cputime_adjusted() to get times for the thread
1077                  * group, which consolidates times for all threads in the
1078                  * group including the group leader.
1079                  */
1080                 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1081                 spin_lock_irq(&p->real_parent->sighand->siglock);
1082                 psig = p->real_parent->signal;
1083                 sig = p->signal;
1084                 psig->cutime += tgutime + sig->cutime;
1085                 psig->cstime += tgstime + sig->cstime;
1086                 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1087                 psig->cmin_flt +=
1088                         p->min_flt + sig->min_flt + sig->cmin_flt;
1089                 psig->cmaj_flt +=
1090                         p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1091                 psig->cnvcsw +=
1092                         p->nvcsw + sig->nvcsw + sig->cnvcsw;
1093                 psig->cnivcsw +=
1094                         p->nivcsw + sig->nivcsw + sig->cnivcsw;
1095                 psig->cinblock +=
1096                         task_io_get_inblock(p) +
1097                         sig->inblock + sig->cinblock;
1098                 psig->coublock +=
1099                         task_io_get_oublock(p) +
1100                         sig->oublock + sig->coublock;
1101                 maxrss = max(sig->maxrss, sig->cmaxrss);
1102                 if (psig->cmaxrss < maxrss)
1103                         psig->cmaxrss = maxrss;
1104                 task_io_accounting_add(&psig->ioac, &p->ioac);
1105                 task_io_accounting_add(&psig->ioac, &sig->ioac);
1106                 spin_unlock_irq(&p->real_parent->sighand->siglock);
1107         }
1108 
1109         /*
1110          * Now we are sure this task is interesting, and no other
1111          * thread can reap it because we set its state to EXIT_DEAD.
1112          */
1113         read_unlock(&tasklist_lock);
1114 
1115         retval = wo->wo_rusage
1116                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1117         status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1118                 ? p->signal->group_exit_code : p->exit_code;
1119         if (!retval && wo->wo_stat)
1120                 retval = put_user(status, wo->wo_stat);
1121 
1122         infop = wo->wo_info;
1123         if (!retval && infop)
1124                 retval = put_user(SIGCHLD, &infop->si_signo);
1125         if (!retval && infop)
1126                 retval = put_user(0, &infop->si_errno);
1127         if (!retval && infop) {
1128                 int why;
1129 
1130                 if ((status & 0x7f) == 0) {
1131                         why = CLD_EXITED;
1132                         status >>= 8;
1133                 } else {
1134                         why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1135                         status &= 0x7f;
1136                 }
1137                 retval = put_user((short)why, &infop->si_code);
1138                 if (!retval)
1139                         retval = put_user(status, &infop->si_status);
1140         }
1141         if (!retval && infop)
1142                 retval = put_user(pid, &infop->si_pid);
1143         if (!retval && infop)
1144                 retval = put_user(uid, &infop->si_uid);
1145         if (!retval)
1146                 retval = pid;
1147 
1148         if (traced) {
1149                 write_lock_irq(&tasklist_lock);
1150                 /* We dropped tasklist, ptracer could die and untrace */
1151                 ptrace_unlink(p);
1152                 /*
1153                  * If this is not a sub-thread, notify the parent.
1154                  * If parent wants a zombie, don't release it now.
1155                  */
1156                 if (thread_group_leader(p) &&
1157                     !do_notify_parent(p, p->exit_signal)) {
1158                         p->exit_state = EXIT_ZOMBIE;
1159                         p = NULL;
1160                 }
1161                 write_unlock_irq(&tasklist_lock);
1162         }
1163         if (p != NULL)
1164                 release_task(p);
1165 
1166         return retval;
1167 }
1168 
1169 static int *task_stopped_code(struct task_struct *p, bool ptrace)
1170 {
1171         if (ptrace) {
1172                 if (task_is_stopped_or_traced(p) &&
1173                     !(p->jobctl & JOBCTL_LISTENING))
1174                         return &p->exit_code;
1175         } else {
1176                 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1177                         return &p->signal->group_exit_code;
1178         }
1179         return NULL;
1180 }
1181 
1182 /**
1183  * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1184  * @wo: wait options
1185  * @ptrace: is the wait for ptrace
1186  * @p: task to wait for
1187  *
1188  * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1189  *
1190  * CONTEXT:
1191  * read_lock(&tasklist_lock), which is released if return value is
1192  * non-zero.  Also, grabs and releases @p->sighand->siglock.
1193  *
1194  * RETURNS:
1195  * 0 if wait condition didn't exist and search for other wait conditions
1196  * should continue.  Non-zero return, -errno on failure and @p's pid on
1197  * success, implies that tasklist_lock is released and wait condition
1198  * search should terminate.
1199  */
1200 static int wait_task_stopped(struct wait_opts *wo,
1201                                 int ptrace, struct task_struct *p)
1202 {
1203         struct siginfo __user *infop;
1204         int retval, exit_code, *p_code, why;
1205         uid_t uid = 0; /* unneeded, required by compiler */
1206         pid_t pid;
1207 
1208         /*
1209          * Traditionally we see ptrace'd stopped tasks regardless of options.
1210          */
1211         if (!ptrace && !(wo->wo_flags & WUNTRACED))
1212                 return 0;
1213 
1214         if (!task_stopped_code(p, ptrace))
1215                 return 0;
1216 
1217         exit_code = 0;
1218         spin_lock_irq(&p->sighand->siglock);
1219 
1220         p_code = task_stopped_code(p, ptrace);
1221         if (unlikely(!p_code))
1222                 goto unlock_sig;
1223 
1224         exit_code = *p_code;
1225         if (!exit_code)
1226                 goto unlock_sig;
1227 
1228         if (!unlikely(wo->wo_flags & WNOWAIT))
1229                 *p_code = 0;
1230 
1231         uid = from_kuid_munged(current_user_ns(), task_uid(p));
1232 unlock_sig:
1233         spin_unlock_irq(&p->sighand->siglock);
1234         if (!exit_code)
1235                 return 0;
1236 
1237         /*
1238          * Now we are pretty sure this task is interesting.
1239          * Make sure it doesn't get reaped out from under us while we
1240          * give up the lock and then examine it below.  We don't want to
1241          * keep holding onto the tasklist_lock while we call getrusage and
1242          * possibly take page faults for user memory.
1243          */
1244         get_task_struct(p);
1245         pid = task_pid_vnr(p);
1246         why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1247         read_unlock(&tasklist_lock);
1248 
1249         if (unlikely(wo->wo_flags & WNOWAIT))
1250                 return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1251 
1252         retval = wo->wo_rusage
1253                 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1254         if (!retval && wo->wo_stat)
1255                 retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1256 
1257         infop = wo->wo_info;
1258         if (!retval && infop)
1259                 retval = put_user(SIGCHLD, &infop->si_signo);
1260         if (!retval && infop)
1261                 retval = put_user(0, &infop->si_errno);
1262         if (!retval && infop)
1263                 retval = put_user((short)why, &infop->si_code);
1264         if (!retval && infop)
1265                 retval = put_user(exit_code, &infop->si_status);
1266         if (!retval && infop)
1267                 retval = put_user(pid, &infop->si_pid);
1268         if (!retval && infop)
1269                 retval = put_user(uid, &infop->si_uid);
1270         if (!retval)
1271                 retval = pid;
1272         put_task_struct(p);
1273 
1274         BUG_ON(!retval);
1275         return retval;
1276 }
1277 
1278 /*
1279  * Handle do_wait work for one task in a live, non-stopped state.
1280  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1281  * the lock and this task is uninteresting.  If we return nonzero, we have
1282  * released the lock and the system call should return.
1283  */
1284 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1285 {
1286         int retval;
1287         pid_t pid;
1288         uid_t uid;
1289 
1290         if (!unlikely(wo->wo_flags & WCONTINUED))
1291                 return 0;
1292 
1293         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1294                 return 0;
1295 
1296         spin_lock_irq(&p->sighand->siglock);
1297         /* Re-check with the lock held.  */
1298         if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1299                 spin_unlock_irq(&p->sighand->siglock);
1300                 return 0;
1301         }
1302         if (!unlikely(wo->wo_flags & WNOWAIT))
1303                 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1304         uid = from_kuid_munged(current_user_ns(), task_uid(p));
1305         spin_unlock_irq(&p->sighand->siglock);
1306 
1307         pid = task_pid_vnr(p);
1308         get_task_struct(p);
1309         read_unlock(&tasklist_lock);
1310 
1311         if (!wo->wo_info) {
1312                 retval = wo->wo_rusage
1313                         ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1314                 put_task_struct(p);
1315                 if (!retval && wo->wo_stat)
1316                         retval = put_user(0xffff, wo->wo_stat);
1317                 if (!retval)
1318                         retval = pid;
1319         } else {
1320                 retval = wait_noreap_copyout(wo, p, pid, uid,
1321                                              CLD_CONTINUED, SIGCONT);
1322                 BUG_ON(retval == 0);
1323         }
1324 
1325         return retval;
1326 }
1327 
1328 /*
1329  * Consider @p for a wait by @parent.
1330  *
1331  * -ECHILD should be in ->notask_error before the first call.
1332  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1333  * Returns zero if the search for a child should continue;
1334  * then ->notask_error is 0 if @p is an eligible child,
1335  * or another error from security_task_wait(), or still -ECHILD.
1336  */
1337 static int wait_consider_task(struct wait_opts *wo, int ptrace,
1338                                 struct task_struct *p)
1339 {
1340         int ret = eligible_child(wo, p);
1341         if (!ret)
1342                 return ret;
1343 
1344         ret = security_task_wait(p);
1345         if (unlikely(ret < 0)) {
1346                 /*
1347                  * If we have not yet seen any eligible child,
1348                  * then let this error code replace -ECHILD.
1349                  * A permission error will give the user a clue
1350                  * to look for security policy problems, rather
1351                  * than for mysterious wait bugs.
1352                  */
1353                 if (wo->notask_error)
1354                         wo->notask_error = ret;
1355                 return 0;
1356         }
1357 
1358         /* dead body doesn't have much to contribute */
1359         if (unlikely(p->exit_state == EXIT_DEAD)) {
1360                 /*
1361                  * But do not ignore this task until the tracer does
1362                  * wait_task_zombie()->do_notify_parent().
1363                  */
1364                 if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
1365                         wo->notask_error = 0;
1366                 return 0;
1367         }
1368 
1369         /* slay zombie? */
1370         if (p->exit_state == EXIT_ZOMBIE) {
1371                 /*
1372                  * A zombie ptracee is only visible to its ptracer.
1373                  * Notification and reaping will be cascaded to the real
1374                  * parent when the ptracer detaches.
1375                  */
1376                 if (likely(!ptrace) && unlikely(p->ptrace)) {
1377                         /* it will become visible, clear notask_error */
1378                         wo->notask_error = 0;
1379                         return 0;
1380                 }
1381 
1382                 /* we don't reap group leaders with subthreads */
1383                 if (!delay_group_leader(p))
1384                         return wait_task_zombie(wo, p);
1385 
1386                 /*
1387                  * Allow access to stopped/continued state via zombie by
1388                  * falling through.  Clearing of notask_error is complex.
1389                  *
1390                  * When !@ptrace:
1391                  *
1392                  * If WEXITED is set, notask_error should naturally be
1393                  * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1394                  * so, if there are live subthreads, there are events to
1395                  * wait for.  If all subthreads are dead, it's still safe
1396                  * to clear - this function will be called again in finite
1397                  * amount time once all the subthreads are released and
1398                  * will then return without clearing.
1399                  *
1400                  * When @ptrace:
1401                  *
1402                  * Stopped state is per-task and thus can't change once the
1403                  * target task dies.  Only continued and exited can happen.
1404                  * Clear notask_error if WCONTINUED | WEXITED.
1405                  */
1406                 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1407                         wo->notask_error = 0;
1408         } else {
1409                 /*
1410                  * If @p is ptraced by a task in its real parent's group,
1411                  * hide group stop/continued state when looking at @p as
1412                  * the real parent; otherwise, a single stop can be
1413                  * reported twice as group and ptrace stops.
1414                  *
1415                  * If a ptracer wants to distinguish the two events for its
1416                  * own children, it should create a separate process which
1417                  * takes the role of real parent.
1418                  */
1419                 if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
1420                         return 0;
1421 
1422                 /*
1423                  * @p is alive and it's gonna stop, continue or exit, so
1424                  * there always is something to wait for.
1425                  */
1426                 wo->notask_error = 0;
1427         }
1428 
1429         /*
1430          * Wait for stopped.  Depending on @ptrace, different stopped state
1431          * is used and the two don't interact with each other.
1432          */
1433         ret = wait_task_stopped(wo, ptrace, p);
1434         if (ret)
1435                 return ret;
1436 
1437         /*
1438          * Wait for continued.  There's only one continued state and the
1439          * ptracer can consume it which can confuse the real parent.  Don't
1440          * use WCONTINUED from ptracer.  You don't need or want it.
1441          */
1442         return wait_task_continued(wo, p);
1443 }
1444 
1445 /*
1446  * Do the work of do_wait() for one thread in the group, @tsk.
1447  *
1448  * -ECHILD should be in ->notask_error before the first call.
1449  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1450  * Returns zero if the search for a child should continue; then
1451  * ->notask_error is 0 if there were any eligible children,
1452  * or another error from security_task_wait(), or still -ECHILD.
1453  */
1454 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1455 {
1456         struct task_struct *p;
1457 
1458         list_for_each_entry(p, &tsk->children, sibling) {
1459                 int ret = wait_consider_task(wo, 0, p);
1460                 if (ret)
1461                         return ret;
1462         }
1463 
1464         return 0;
1465 }
1466 
1467 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1468 {
1469         struct task_struct *p;
1470 
1471         list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1472                 int ret = wait_consider_task(wo, 1, p);
1473                 if (ret)
1474                         return ret;
1475         }
1476 
1477         return 0;
1478 }
1479 
1480 static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1481                                 int sync, void *key)
1482 {
1483         struct wait_opts *wo = container_of(wait, struct wait_opts,
1484                                                 child_wait);
1485         struct task_struct *p = key;
1486 
1487         if (!eligible_pid(wo, p))
1488                 return 0;
1489 
1490         if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1491                 return 0;
1492 
1493         return default_wake_function(wait, mode, sync, key);
1494 }
1495 
1496 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1497 {
1498         __wake_up_sync_key(&parent->signal->wait_chldexit,
1499                                 TASK_INTERRUPTIBLE, 1, p);
1500 }
1501 
1502 static long do_wait(struct wait_opts *wo)
1503 {
1504         struct task_struct *tsk;
1505         int retval;
1506 
1507         trace_sched_process_wait(wo->wo_pid);
1508 
1509         init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1510         wo->child_wait.private = current;
1511         add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1512 repeat:
1513         /*
1514          * If there is nothing that can match our critiera just get out.
1515          * We will clear ->notask_error to zero if we see any child that
1516          * might later match our criteria, even if we are not able to reap
1517          * it yet.
1518          */
1519         wo->notask_error = -ECHILD;
1520         if ((wo->wo_type < PIDTYPE_MAX) &&
1521            (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1522                 goto notask;
1523 
1524         set_current_state(TASK_INTERRUPTIBLE);
1525         read_lock(&tasklist_lock);
1526         tsk = current;
1527         do {
1528                 retval = do_wait_thread(wo, tsk);
1529                 if (retval)
1530                         goto end;
1531 
1532                 retval = ptrace_do_wait(wo, tsk);
1533                 if (retval)
1534                         goto end;
1535 
1536                 if (wo->wo_flags & __WNOTHREAD)
1537                         break;
1538         } while_each_thread(current, tsk);
1539         read_unlock(&tasklist_lock);
1540 
1541 notask:
1542         retval = wo->notask_error;
1543         if (!retval && !(wo->wo_flags & WNOHANG)) {
1544                 retval = -ERESTARTSYS;
1545                 if (!signal_pending(current)) {
1546                         schedule();
1547                         goto repeat;
1548                 }
1549         }
1550 end:
1551         __set_current_state(TASK_RUNNING);
1552         remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1553         return retval;
1554 }
1555 
1556 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1557                 infop, int, options, struct rusage __user *, ru)
1558 {
1559         struct wait_opts wo;
1560         struct pid *pid = NULL;
1561         enum pid_type type;
1562         long ret;
1563 
1564         if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1565                 return -EINVAL;
1566         if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1567                 return -EINVAL;
1568 
1569         switch (which) {
1570         case P_ALL:
1571                 type = PIDTYPE_MAX;
1572                 break;
1573         case P_PID:
1574                 type = PIDTYPE_PID;
1575                 if (upid <= 0)
1576                         return -EINVAL;
1577                 break;
1578         case P_PGID:
1579                 type = PIDTYPE_PGID;
1580                 if (upid <= 0)
1581                         return -EINVAL;
1582                 break;
1583         default:
1584                 return -EINVAL;
1585         }
1586 
1587         if (type < PIDTYPE_MAX)
1588                 pid = find_get_pid(upid);
1589 
1590         wo.wo_type      = type;
1591         wo.wo_pid       = pid;
1592         wo.wo_flags     = options;
1593         wo.wo_info      = infop;
1594         wo.wo_stat      = NULL;
1595         wo.wo_rusage    = ru;
1596         ret = do_wait(&wo);
1597 
1598         if (ret > 0) {
1599                 ret = 0;
1600         } else if (infop) {
1601                 /*
1602                  * For a WNOHANG return, clear out all the fields
1603                  * we would set so the user can easily tell the
1604                  * difference.
1605                  */
1606                 if (!ret)
1607                         ret = put_user(0, &infop->si_signo);
1608                 if (!ret)
1609                         ret = put_user(0, &infop->si_errno);
1610                 if (!ret)
1611                         ret = put_user(0, &infop->si_code);
1612                 if (!ret)
1613                         ret = put_user(0, &infop->si_pid);
1614                 if (!ret)
1615                         ret = put_user(0, &infop->si_uid);
1616                 if (!ret)
1617                         ret = put_user(0, &infop->si_status);
1618         }
1619 
1620         put_pid(pid);
1621         return ret;
1622 }
1623 
1624 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1625                 int, options, struct rusage __user *, ru)
1626 {
1627         struct wait_opts wo;
1628         struct pid *pid = NULL;
1629         enum pid_type type;
1630         long ret;
1631 
1632         if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1633                         __WNOTHREAD|__WCLONE|__WALL))
1634                 return -EINVAL;
1635 
1636         if (upid == -1)
1637                 type = PIDTYPE_MAX;
1638         else if (upid < 0) {
1639                 type = PIDTYPE_PGID;
1640                 pid = find_get_pid(-upid);
1641         } else if (upid == 0) {
1642                 type = PIDTYPE_PGID;
1643                 pid = get_task_pid(current, PIDTYPE_PGID);
1644         } else /* upid > 0 */ {
1645                 type = PIDTYPE_PID;
1646                 pid = find_get_pid(upid);
1647         }
1648 
1649         wo.wo_type      = type;
1650         wo.wo_pid       = pid;
1651         wo.wo_flags     = options | WEXITED;
1652         wo.wo_info      = NULL;
1653         wo.wo_stat      = stat_addr;
1654         wo.wo_rusage    = ru;
1655         ret = do_wait(&wo);
1656         put_pid(pid);
1657 
1658         return ret;
1659 }
1660 
1661 #ifdef __ARCH_WANT_SYS_WAITPID
1662 
1663 /*
1664  * sys_waitpid() remains for compatibility. waitpid() should be
1665  * implemented by calling sys_wait4() from libc.a.
1666  */
1667 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1668 {
1669         return sys_wait4(pid, stat_addr, options, NULL);
1670 }
1671 
1672 #endif
1673 

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