]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - kernel/exit.c
Merge tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[mirror_ubuntu-bionic-kernel.git] / 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/sched/autogroup.h>
10 #include <linux/sched/mm.h>
11 #include <linux/sched/stat.h>
12 #include <linux/sched/task.h>
13 #include <linux/sched/task_stack.h>
14 #include <linux/sched/cputime.h>
15 #include <linux/interrupt.h>
16 #include <linux/module.h>
17 #include <linux/capability.h>
18 #include <linux/completion.h>
19 #include <linux/personality.h>
20 #include <linux/tty.h>
21 #include <linux/iocontext.h>
22 #include <linux/key.h>
23 #include <linux/cpu.h>
24 #include <linux/acct.h>
25 #include <linux/tsacct_kern.h>
26 #include <linux/file.h>
27 #include <linux/fdtable.h>
28 #include <linux/freezer.h>
29 #include <linux/binfmts.h>
30 #include <linux/nsproxy.h>
31 #include <linux/pid_namespace.h>
32 #include <linux/ptrace.h>
33 #include <linux/profile.h>
34 #include <linux/mount.h>
35 #include <linux/proc_fs.h>
36 #include <linux/kthread.h>
37 #include <linux/mempolicy.h>
38 #include <linux/taskstats_kern.h>
39 #include <linux/delayacct.h>
40 #include <linux/cgroup.h>
41 #include <linux/syscalls.h>
42 #include <linux/signal.h>
43 #include <linux/posix-timers.h>
44 #include <linux/cn_proc.h>
45 #include <linux/mutex.h>
46 #include <linux/futex.h>
47 #include <linux/pipe_fs_i.h>
48 #include <linux/audit.h> /* for audit_free() */
49 #include <linux/resource.h>
50 #include <linux/blkdev.h>
51 #include <linux/task_io_accounting_ops.h>
52 #include <linux/tracehook.h>
53 #include <linux/fs_struct.h>
54 #include <linux/userfaultfd_k.h>
55 #include <linux/init_task.h>
56 #include <linux/perf_event.h>
57 #include <trace/events/sched.h>
58 #include <linux/hw_breakpoint.h>
59 #include <linux/oom.h>
60 #include <linux/writeback.h>
61 #include <linux/shm.h>
62 #include <linux/kcov.h>
63 #include <linux/random.h>
64 #include <linux/rcuwait.h>
65
66 #include <linux/uaccess.h>
67 #include <asm/unistd.h>
68 #include <asm/pgtable.h>
69 #include <asm/mmu_context.h>
70
71 static void __unhash_process(struct task_struct *p, bool group_dead)
72 {
73 nr_threads--;
74 detach_pid(p, PIDTYPE_PID);
75 if (group_dead) {
76 detach_pid(p, PIDTYPE_PGID);
77 detach_pid(p, PIDTYPE_SID);
78
79 list_del_rcu(&p->tasks);
80 list_del_init(&p->sibling);
81 __this_cpu_dec(process_counts);
82 }
83 list_del_rcu(&p->thread_group);
84 list_del_rcu(&p->thread_node);
85 }
86
87 /*
88 * This function expects the tasklist_lock write-locked.
89 */
90 static void __exit_signal(struct task_struct *tsk)
91 {
92 struct signal_struct *sig = tsk->signal;
93 bool group_dead = thread_group_leader(tsk);
94 struct sighand_struct *sighand;
95 struct tty_struct *uninitialized_var(tty);
96 u64 utime, stime;
97
98 sighand = rcu_dereference_check(tsk->sighand,
99 lockdep_tasklist_lock_is_held());
100 spin_lock(&sighand->siglock);
101
102 #ifdef CONFIG_POSIX_TIMERS
103 posix_cpu_timers_exit(tsk);
104 if (group_dead) {
105 posix_cpu_timers_exit_group(tsk);
106 } else {
107 /*
108 * This can only happen if the caller is de_thread().
109 * FIXME: this is the temporary hack, we should teach
110 * posix-cpu-timers to handle this case correctly.
111 */
112 if (unlikely(has_group_leader_pid(tsk)))
113 posix_cpu_timers_exit_group(tsk);
114 }
115 #endif
116
117 if (group_dead) {
118 tty = sig->tty;
119 sig->tty = NULL;
120 } else {
121 /*
122 * If there is any task waiting for the group exit
123 * then notify it:
124 */
125 if (sig->notify_count > 0 && !--sig->notify_count)
126 wake_up_process(sig->group_exit_task);
127
128 if (tsk == sig->curr_target)
129 sig->curr_target = next_thread(tsk);
130 }
131
132 add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
133 sizeof(unsigned long long));
134
135 /*
136 * Accumulate here the counters for all threads as they die. We could
137 * skip the group leader because it is the last user of signal_struct,
138 * but we want to avoid the race with thread_group_cputime() which can
139 * see the empty ->thread_head list.
140 */
141 task_cputime(tsk, &utime, &stime);
142 write_seqlock(&sig->stats_lock);
143 sig->utime += utime;
144 sig->stime += stime;
145 sig->gtime += task_gtime(tsk);
146 sig->min_flt += tsk->min_flt;
147 sig->maj_flt += tsk->maj_flt;
148 sig->nvcsw += tsk->nvcsw;
149 sig->nivcsw += tsk->nivcsw;
150 sig->inblock += task_io_get_inblock(tsk);
151 sig->oublock += task_io_get_oublock(tsk);
152 task_io_accounting_add(&sig->ioac, &tsk->ioac);
153 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
154 sig->nr_threads--;
155 __unhash_process(tsk, group_dead);
156 write_sequnlock(&sig->stats_lock);
157
158 /*
159 * Do this under ->siglock, we can race with another thread
160 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
161 */
162 flush_sigqueue(&tsk->pending);
163 tsk->sighand = NULL;
164 spin_unlock(&sighand->siglock);
165
166 __cleanup_sighand(sighand);
167 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
168 if (group_dead) {
169 flush_sigqueue(&sig->shared_pending);
170 tty_kref_put(tty);
171 }
172 }
173
174 static void delayed_put_task_struct(struct rcu_head *rhp)
175 {
176 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
177
178 perf_event_delayed_put(tsk);
179 trace_sched_process_free(tsk);
180 put_task_struct(tsk);
181 }
182
183
184 void release_task(struct task_struct *p)
185 {
186 struct task_struct *leader;
187 int zap_leader;
188 repeat:
189 /* don't need to get the RCU readlock here - the process is dead and
190 * can't be modifying its own credentials. But shut RCU-lockdep up */
191 rcu_read_lock();
192 atomic_dec(&__task_cred(p)->user->processes);
193 rcu_read_unlock();
194
195 proc_flush_task(p);
196
197 write_lock_irq(&tasklist_lock);
198 ptrace_release_task(p);
199 __exit_signal(p);
200
201 /*
202 * If we are the last non-leader member of the thread
203 * group, and the leader is zombie, then notify the
204 * group leader's parent process. (if it wants notification.)
205 */
206 zap_leader = 0;
207 leader = p->group_leader;
208 if (leader != p && thread_group_empty(leader)
209 && leader->exit_state == EXIT_ZOMBIE) {
210 /*
211 * If we were the last child thread and the leader has
212 * exited already, and the leader's parent ignores SIGCHLD,
213 * then we are the one who should release the leader.
214 */
215 zap_leader = do_notify_parent(leader, leader->exit_signal);
216 if (zap_leader)
217 leader->exit_state = EXIT_DEAD;
218 }
219
220 write_unlock_irq(&tasklist_lock);
221 release_thread(p);
222 call_rcu(&p->rcu, delayed_put_task_struct);
223
224 p = leader;
225 if (unlikely(zap_leader))
226 goto repeat;
227 }
228
229 /*
230 * Note that if this function returns a valid task_struct pointer (!NULL)
231 * task->usage must remain >0 for the duration of the RCU critical section.
232 */
233 struct task_struct *task_rcu_dereference(struct task_struct **ptask)
234 {
235 struct sighand_struct *sighand;
236 struct task_struct *task;
237
238 /*
239 * We need to verify that release_task() was not called and thus
240 * delayed_put_task_struct() can't run and drop the last reference
241 * before rcu_read_unlock(). We check task->sighand != NULL,
242 * but we can read the already freed and reused memory.
243 */
244 retry:
245 task = rcu_dereference(*ptask);
246 if (!task)
247 return NULL;
248
249 probe_kernel_address(&task->sighand, sighand);
250
251 /*
252 * Pairs with atomic_dec_and_test() in put_task_struct(). If this task
253 * was already freed we can not miss the preceding update of this
254 * pointer.
255 */
256 smp_rmb();
257 if (unlikely(task != READ_ONCE(*ptask)))
258 goto retry;
259
260 /*
261 * We've re-checked that "task == *ptask", now we have two different
262 * cases:
263 *
264 * 1. This is actually the same task/task_struct. In this case
265 * sighand != NULL tells us it is still alive.
266 *
267 * 2. This is another task which got the same memory for task_struct.
268 * We can't know this of course, and we can not trust
269 * sighand != NULL.
270 *
271 * In this case we actually return a random value, but this is
272 * correct.
273 *
274 * If we return NULL - we can pretend that we actually noticed that
275 * *ptask was updated when the previous task has exited. Or pretend
276 * that probe_slab_address(&sighand) reads NULL.
277 *
278 * If we return the new task (because sighand is not NULL for any
279 * reason) - this is fine too. This (new) task can't go away before
280 * another gp pass.
281 *
282 * And note: We could even eliminate the false positive if re-read
283 * task->sighand once again to avoid the falsely NULL. But this case
284 * is very unlikely so we don't care.
285 */
286 if (!sighand)
287 return NULL;
288
289 return task;
290 }
291
292 void rcuwait_wake_up(struct rcuwait *w)
293 {
294 struct task_struct *task;
295
296 rcu_read_lock();
297
298 /*
299 * Order condition vs @task, such that everything prior to the load
300 * of @task is visible. This is the condition as to why the user called
301 * rcuwait_trywake() in the first place. Pairs with set_current_state()
302 * barrier (A) in rcuwait_wait_event().
303 *
304 * WAIT WAKE
305 * [S] tsk = current [S] cond = true
306 * MB (A) MB (B)
307 * [L] cond [L] tsk
308 */
309 smp_rmb(); /* (B) */
310
311 /*
312 * Avoid using task_rcu_dereference() magic as long as we are careful,
313 * see comment in rcuwait_wait_event() regarding ->exit_state.
314 */
315 task = rcu_dereference(w->task);
316 if (task)
317 wake_up_process(task);
318 rcu_read_unlock();
319 }
320
321 struct task_struct *try_get_task_struct(struct task_struct **ptask)
322 {
323 struct task_struct *task;
324
325 rcu_read_lock();
326 task = task_rcu_dereference(ptask);
327 if (task)
328 get_task_struct(task);
329 rcu_read_unlock();
330
331 return task;
332 }
333
334 /*
335 * Determine if a process group is "orphaned", according to the POSIX
336 * definition in 2.2.2.52. Orphaned process groups are not to be affected
337 * by terminal-generated stop signals. Newly orphaned process groups are
338 * to receive a SIGHUP and a SIGCONT.
339 *
340 * "I ask you, have you ever known what it is to be an orphan?"
341 */
342 static int will_become_orphaned_pgrp(struct pid *pgrp,
343 struct task_struct *ignored_task)
344 {
345 struct task_struct *p;
346
347 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
348 if ((p == ignored_task) ||
349 (p->exit_state && thread_group_empty(p)) ||
350 is_global_init(p->real_parent))
351 continue;
352
353 if (task_pgrp(p->real_parent) != pgrp &&
354 task_session(p->real_parent) == task_session(p))
355 return 0;
356 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
357
358 return 1;
359 }
360
361 int is_current_pgrp_orphaned(void)
362 {
363 int retval;
364
365 read_lock(&tasklist_lock);
366 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
367 read_unlock(&tasklist_lock);
368
369 return retval;
370 }
371
372 static bool has_stopped_jobs(struct pid *pgrp)
373 {
374 struct task_struct *p;
375
376 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
377 if (p->signal->flags & SIGNAL_STOP_STOPPED)
378 return true;
379 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
380
381 return false;
382 }
383
384 /*
385 * Check to see if any process groups have become orphaned as
386 * a result of our exiting, and if they have any stopped jobs,
387 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
388 */
389 static void
390 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
391 {
392 struct pid *pgrp = task_pgrp(tsk);
393 struct task_struct *ignored_task = tsk;
394
395 if (!parent)
396 /* exit: our father is in a different pgrp than
397 * we are and we were the only connection outside.
398 */
399 parent = tsk->real_parent;
400 else
401 /* reparent: our child is in a different pgrp than
402 * we are, and it was the only connection outside.
403 */
404 ignored_task = NULL;
405
406 if (task_pgrp(parent) != pgrp &&
407 task_session(parent) == task_session(tsk) &&
408 will_become_orphaned_pgrp(pgrp, ignored_task) &&
409 has_stopped_jobs(pgrp)) {
410 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
411 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
412 }
413 }
414
415 #ifdef CONFIG_MEMCG
416 /*
417 * A task is exiting. If it owned this mm, find a new owner for the mm.
418 */
419 void mm_update_next_owner(struct mm_struct *mm)
420 {
421 struct task_struct *c, *g, *p = current;
422
423 retry:
424 /*
425 * If the exiting or execing task is not the owner, it's
426 * someone else's problem.
427 */
428 if (mm->owner != p)
429 return;
430 /*
431 * The current owner is exiting/execing and there are no other
432 * candidates. Do not leave the mm pointing to a possibly
433 * freed task structure.
434 */
435 if (atomic_read(&mm->mm_users) <= 1) {
436 mm->owner = NULL;
437 return;
438 }
439
440 read_lock(&tasklist_lock);
441 /*
442 * Search in the children
443 */
444 list_for_each_entry(c, &p->children, sibling) {
445 if (c->mm == mm)
446 goto assign_new_owner;
447 }
448
449 /*
450 * Search in the siblings
451 */
452 list_for_each_entry(c, &p->real_parent->children, sibling) {
453 if (c->mm == mm)
454 goto assign_new_owner;
455 }
456
457 /*
458 * Search through everything else, we should not get here often.
459 */
460 for_each_process(g) {
461 if (g->flags & PF_KTHREAD)
462 continue;
463 for_each_thread(g, c) {
464 if (c->mm == mm)
465 goto assign_new_owner;
466 if (c->mm)
467 break;
468 }
469 }
470 read_unlock(&tasklist_lock);
471 /*
472 * We found no owner yet mm_users > 1: this implies that we are
473 * most likely racing with swapoff (try_to_unuse()) or /proc or
474 * ptrace or page migration (get_task_mm()). Mark owner as NULL.
475 */
476 mm->owner = NULL;
477 return;
478
479 assign_new_owner:
480 BUG_ON(c == p);
481 get_task_struct(c);
482 /*
483 * The task_lock protects c->mm from changing.
484 * We always want mm->owner->mm == mm
485 */
486 task_lock(c);
487 /*
488 * Delay read_unlock() till we have the task_lock()
489 * to ensure that c does not slip away underneath us
490 */
491 read_unlock(&tasklist_lock);
492 if (c->mm != mm) {
493 task_unlock(c);
494 put_task_struct(c);
495 goto retry;
496 }
497 mm->owner = c;
498 task_unlock(c);
499 put_task_struct(c);
500 }
501 #endif /* CONFIG_MEMCG */
502
503 /*
504 * Turn us into a lazy TLB process if we
505 * aren't already..
506 */
507 static void exit_mm(void)
508 {
509 struct mm_struct *mm = current->mm;
510 struct core_state *core_state;
511
512 mm_release(current, mm);
513 if (!mm)
514 return;
515 sync_mm_rss(mm);
516 /*
517 * Serialize with any possible pending coredump.
518 * We must hold mmap_sem around checking core_state
519 * and clearing tsk->mm. The core-inducing thread
520 * will increment ->nr_threads for each thread in the
521 * group with ->mm != NULL.
522 */
523 down_read(&mm->mmap_sem);
524 core_state = mm->core_state;
525 if (core_state) {
526 struct core_thread self;
527
528 up_read(&mm->mmap_sem);
529
530 self.task = current;
531 self.next = xchg(&core_state->dumper.next, &self);
532 /*
533 * Implies mb(), the result of xchg() must be visible
534 * to core_state->dumper.
535 */
536 if (atomic_dec_and_test(&core_state->nr_threads))
537 complete(&core_state->startup);
538
539 for (;;) {
540 set_current_state(TASK_UNINTERRUPTIBLE);
541 if (!self.task) /* see coredump_finish() */
542 break;
543 freezable_schedule();
544 }
545 __set_current_state(TASK_RUNNING);
546 down_read(&mm->mmap_sem);
547 }
548 mmgrab(mm);
549 BUG_ON(mm != current->active_mm);
550 /* more a memory barrier than a real lock */
551 task_lock(current);
552 current->mm = NULL;
553 up_read(&mm->mmap_sem);
554 enter_lazy_tlb(mm, current);
555 task_unlock(current);
556 mm_update_next_owner(mm);
557 mmput(mm);
558 if (test_thread_flag(TIF_MEMDIE))
559 exit_oom_victim();
560 }
561
562 static struct task_struct *find_alive_thread(struct task_struct *p)
563 {
564 struct task_struct *t;
565
566 for_each_thread(p, t) {
567 if (!(t->flags & PF_EXITING))
568 return t;
569 }
570 return NULL;
571 }
572
573 static struct task_struct *find_child_reaper(struct task_struct *father)
574 __releases(&tasklist_lock)
575 __acquires(&tasklist_lock)
576 {
577 struct pid_namespace *pid_ns = task_active_pid_ns(father);
578 struct task_struct *reaper = pid_ns->child_reaper;
579
580 if (likely(reaper != father))
581 return reaper;
582
583 reaper = find_alive_thread(father);
584 if (reaper) {
585 pid_ns->child_reaper = reaper;
586 return reaper;
587 }
588
589 write_unlock_irq(&tasklist_lock);
590 if (unlikely(pid_ns == &init_pid_ns)) {
591 panic("Attempted to kill init! exitcode=0x%08x\n",
592 father->signal->group_exit_code ?: father->exit_code);
593 }
594 zap_pid_ns_processes(pid_ns);
595 write_lock_irq(&tasklist_lock);
596
597 return father;
598 }
599
600 /*
601 * When we die, we re-parent all our children, and try to:
602 * 1. give them to another thread in our thread group, if such a member exists
603 * 2. give it to the first ancestor process which prctl'd itself as a
604 * child_subreaper for its children (like a service manager)
605 * 3. give it to the init process (PID 1) in our pid namespace
606 */
607 static struct task_struct *find_new_reaper(struct task_struct *father,
608 struct task_struct *child_reaper)
609 {
610 struct task_struct *thread, *reaper;
611
612 thread = find_alive_thread(father);
613 if (thread)
614 return thread;
615
616 if (father->signal->has_child_subreaper) {
617 unsigned int ns_level = task_pid(father)->level;
618 /*
619 * Find the first ->is_child_subreaper ancestor in our pid_ns.
620 * We can't check reaper != child_reaper to ensure we do not
621 * cross the namespaces, the exiting parent could be injected
622 * by setns() + fork().
623 * We check pid->level, this is slightly more efficient than
624 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
625 */
626 for (reaper = father->real_parent;
627 task_pid(reaper)->level == ns_level;
628 reaper = reaper->real_parent) {
629 if (reaper == &init_task)
630 break;
631 if (!reaper->signal->is_child_subreaper)
632 continue;
633 thread = find_alive_thread(reaper);
634 if (thread)
635 return thread;
636 }
637 }
638
639 return child_reaper;
640 }
641
642 /*
643 * Any that need to be release_task'd are put on the @dead list.
644 */
645 static void reparent_leader(struct task_struct *father, struct task_struct *p,
646 struct list_head *dead)
647 {
648 if (unlikely(p->exit_state == EXIT_DEAD))
649 return;
650
651 /* We don't want people slaying init. */
652 p->exit_signal = SIGCHLD;
653
654 /* If it has exited notify the new parent about this child's death. */
655 if (!p->ptrace &&
656 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
657 if (do_notify_parent(p, p->exit_signal)) {
658 p->exit_state = EXIT_DEAD;
659 list_add(&p->ptrace_entry, dead);
660 }
661 }
662
663 kill_orphaned_pgrp(p, father);
664 }
665
666 /*
667 * This does two things:
668 *
669 * A. Make init inherit all the child processes
670 * B. Check to see if any process groups have become orphaned
671 * as a result of our exiting, and if they have any stopped
672 * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
673 */
674 static void forget_original_parent(struct task_struct *father,
675 struct list_head *dead)
676 {
677 struct task_struct *p, *t, *reaper;
678
679 if (unlikely(!list_empty(&father->ptraced)))
680 exit_ptrace(father, dead);
681
682 /* Can drop and reacquire tasklist_lock */
683 reaper = find_child_reaper(father);
684 if (list_empty(&father->children))
685 return;
686
687 reaper = find_new_reaper(father, reaper);
688 list_for_each_entry(p, &father->children, sibling) {
689 for_each_thread(p, t) {
690 t->real_parent = reaper;
691 BUG_ON((!t->ptrace) != (t->parent == father));
692 if (likely(!t->ptrace))
693 t->parent = t->real_parent;
694 if (t->pdeath_signal)
695 group_send_sig_info(t->pdeath_signal,
696 SEND_SIG_NOINFO, t);
697 }
698 /*
699 * If this is a threaded reparent there is no need to
700 * notify anyone anything has happened.
701 */
702 if (!same_thread_group(reaper, father))
703 reparent_leader(father, p, dead);
704 }
705 list_splice_tail_init(&father->children, &reaper->children);
706 }
707
708 /*
709 * Send signals to all our closest relatives so that they know
710 * to properly mourn us..
711 */
712 static void exit_notify(struct task_struct *tsk, int group_dead)
713 {
714 bool autoreap;
715 struct task_struct *p, *n;
716 LIST_HEAD(dead);
717
718 write_lock_irq(&tasklist_lock);
719 forget_original_parent(tsk, &dead);
720
721 if (group_dead)
722 kill_orphaned_pgrp(tsk->group_leader, NULL);
723
724 if (unlikely(tsk->ptrace)) {
725 int sig = thread_group_leader(tsk) &&
726 thread_group_empty(tsk) &&
727 !ptrace_reparented(tsk) ?
728 tsk->exit_signal : SIGCHLD;
729 autoreap = do_notify_parent(tsk, sig);
730 } else if (thread_group_leader(tsk)) {
731 autoreap = thread_group_empty(tsk) &&
732 do_notify_parent(tsk, tsk->exit_signal);
733 } else {
734 autoreap = true;
735 }
736
737 tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
738 if (tsk->exit_state == EXIT_DEAD)
739 list_add(&tsk->ptrace_entry, &dead);
740
741 /* mt-exec, de_thread() is waiting for group leader */
742 if (unlikely(tsk->signal->notify_count < 0))
743 wake_up_process(tsk->signal->group_exit_task);
744 write_unlock_irq(&tasklist_lock);
745
746 list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
747 list_del_init(&p->ptrace_entry);
748 release_task(p);
749 }
750 }
751
752 #ifdef CONFIG_DEBUG_STACK_USAGE
753 static void check_stack_usage(void)
754 {
755 static DEFINE_SPINLOCK(low_water_lock);
756 static int lowest_to_date = THREAD_SIZE;
757 unsigned long free;
758
759 free = stack_not_used(current);
760
761 if (free >= lowest_to_date)
762 return;
763
764 spin_lock(&low_water_lock);
765 if (free < lowest_to_date) {
766 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
767 current->comm, task_pid_nr(current), free);
768 lowest_to_date = free;
769 }
770 spin_unlock(&low_water_lock);
771 }
772 #else
773 static inline void check_stack_usage(void) {}
774 #endif
775
776 void __noreturn do_exit(long code)
777 {
778 struct task_struct *tsk = current;
779 int group_dead;
780 TASKS_RCU(int tasks_rcu_i);
781
782 profile_task_exit(tsk);
783 kcov_task_exit(tsk);
784
785 WARN_ON(blk_needs_flush_plug(tsk));
786
787 if (unlikely(in_interrupt()))
788 panic("Aiee, killing interrupt handler!");
789 if (unlikely(!tsk->pid))
790 panic("Attempted to kill the idle task!");
791
792 /*
793 * If do_exit is called because this processes oopsed, it's possible
794 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
795 * continuing. Amongst other possible reasons, this is to prevent
796 * mm_release()->clear_child_tid() from writing to a user-controlled
797 * kernel address.
798 */
799 set_fs(USER_DS);
800
801 ptrace_event(PTRACE_EVENT_EXIT, code);
802
803 validate_creds_for_do_exit(tsk);
804
805 /*
806 * We're taking recursive faults here in do_exit. Safest is to just
807 * leave this task alone and wait for reboot.
808 */
809 if (unlikely(tsk->flags & PF_EXITING)) {
810 pr_alert("Fixing recursive fault but reboot is needed!\n");
811 /*
812 * We can do this unlocked here. The futex code uses
813 * this flag just to verify whether the pi state
814 * cleanup has been done or not. In the worst case it
815 * loops once more. We pretend that the cleanup was
816 * done as there is no way to return. Either the
817 * OWNER_DIED bit is set by now or we push the blocked
818 * task into the wait for ever nirwana as well.
819 */
820 tsk->flags |= PF_EXITPIDONE;
821 set_current_state(TASK_UNINTERRUPTIBLE);
822 schedule();
823 }
824
825 exit_signals(tsk); /* sets PF_EXITING */
826 /*
827 * Ensure that all new tsk->pi_lock acquisitions must observe
828 * PF_EXITING. Serializes against futex.c:attach_to_pi_owner().
829 */
830 smp_mb();
831 /*
832 * Ensure that we must observe the pi_state in exit_mm() ->
833 * mm_release() -> exit_pi_state_list().
834 */
835 raw_spin_unlock_wait(&tsk->pi_lock);
836
837 if (unlikely(in_atomic())) {
838 pr_info("note: %s[%d] exited with preempt_count %d\n",
839 current->comm, task_pid_nr(current),
840 preempt_count());
841 preempt_count_set(PREEMPT_ENABLED);
842 }
843
844 /* sync mm's RSS info before statistics gathering */
845 if (tsk->mm)
846 sync_mm_rss(tsk->mm);
847 acct_update_integrals(tsk);
848 group_dead = atomic_dec_and_test(&tsk->signal->live);
849 if (group_dead) {
850 #ifdef CONFIG_POSIX_TIMERS
851 hrtimer_cancel(&tsk->signal->real_timer);
852 exit_itimers(tsk->signal);
853 #endif
854 if (tsk->mm)
855 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
856 }
857 acct_collect(code, group_dead);
858 if (group_dead)
859 tty_audit_exit();
860 audit_free(tsk);
861
862 tsk->exit_code = code;
863 taskstats_exit(tsk, group_dead);
864
865 exit_mm();
866
867 if (group_dead)
868 acct_process();
869 trace_sched_process_exit(tsk);
870
871 exit_sem(tsk);
872 exit_shm(tsk);
873 exit_files(tsk);
874 exit_fs(tsk);
875 if (group_dead)
876 disassociate_ctty(1);
877 exit_task_namespaces(tsk);
878 exit_task_work(tsk);
879 exit_thread(tsk);
880
881 /*
882 * Flush inherited counters to the parent - before the parent
883 * gets woken up by child-exit notifications.
884 *
885 * because of cgroup mode, must be called before cgroup_exit()
886 */
887 perf_event_exit_task(tsk);
888
889 sched_autogroup_exit_task(tsk);
890 cgroup_exit(tsk);
891
892 /*
893 * FIXME: do that only when needed, using sched_exit tracepoint
894 */
895 flush_ptrace_hw_breakpoint(tsk);
896
897 TASKS_RCU(preempt_disable());
898 TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
899 TASKS_RCU(preempt_enable());
900 exit_notify(tsk, group_dead);
901 proc_exit_connector(tsk);
902 mpol_put_task_policy(tsk);
903 #ifdef CONFIG_FUTEX
904 if (unlikely(current->pi_state_cache))
905 kfree(current->pi_state_cache);
906 #endif
907 /*
908 * Make sure we are holding no locks:
909 */
910 debug_check_no_locks_held();
911 /*
912 * We can do this unlocked here. The futex code uses this flag
913 * just to verify whether the pi state cleanup has been done
914 * or not. In the worst case it loops once more.
915 */
916 tsk->flags |= PF_EXITPIDONE;
917
918 if (tsk->io_context)
919 exit_io_context(tsk);
920
921 if (tsk->splice_pipe)
922 free_pipe_info(tsk->splice_pipe);
923
924 if (tsk->task_frag.page)
925 put_page(tsk->task_frag.page);
926
927 validate_creds_for_do_exit(tsk);
928
929 check_stack_usage();
930 preempt_disable();
931 if (tsk->nr_dirtied)
932 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
933 exit_rcu();
934 TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i));
935
936 do_task_dead();
937 }
938 EXPORT_SYMBOL_GPL(do_exit);
939
940 void complete_and_exit(struct completion *comp, long code)
941 {
942 if (comp)
943 complete(comp);
944
945 do_exit(code);
946 }
947 EXPORT_SYMBOL(complete_and_exit);
948
949 SYSCALL_DEFINE1(exit, int, error_code)
950 {
951 do_exit((error_code&0xff)<<8);
952 }
953
954 /*
955 * Take down every thread in the group. This is called by fatal signals
956 * as well as by sys_exit_group (below).
957 */
958 void
959 do_group_exit(int exit_code)
960 {
961 struct signal_struct *sig = current->signal;
962
963 BUG_ON(exit_code & 0x80); /* core dumps don't get here */
964
965 if (signal_group_exit(sig))
966 exit_code = sig->group_exit_code;
967 else if (!thread_group_empty(current)) {
968 struct sighand_struct *const sighand = current->sighand;
969
970 spin_lock_irq(&sighand->siglock);
971 if (signal_group_exit(sig))
972 /* Another thread got here before we took the lock. */
973 exit_code = sig->group_exit_code;
974 else {
975 sig->group_exit_code = exit_code;
976 sig->flags = SIGNAL_GROUP_EXIT;
977 zap_other_threads(current);
978 }
979 spin_unlock_irq(&sighand->siglock);
980 }
981
982 do_exit(exit_code);
983 /* NOTREACHED */
984 }
985
986 /*
987 * this kills every thread in the thread group. Note that any externally
988 * wait4()-ing process will get the correct exit code - even if this
989 * thread is not the thread group leader.
990 */
991 SYSCALL_DEFINE1(exit_group, int, error_code)
992 {
993 do_group_exit((error_code & 0xff) << 8);
994 /* NOTREACHED */
995 return 0;
996 }
997
998 struct wait_opts {
999 enum pid_type wo_type;
1000 int wo_flags;
1001 struct pid *wo_pid;
1002
1003 struct siginfo __user *wo_info;
1004 int __user *wo_stat;
1005 struct rusage __user *wo_rusage;
1006
1007 wait_queue_t child_wait;
1008 int notask_error;
1009 };
1010
1011 static inline
1012 struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1013 {
1014 if (type != PIDTYPE_PID)
1015 task = task->group_leader;
1016 return task->pids[type].pid;
1017 }
1018
1019 static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1020 {
1021 return wo->wo_type == PIDTYPE_MAX ||
1022 task_pid_type(p, wo->wo_type) == wo->wo_pid;
1023 }
1024
1025 static int
1026 eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
1027 {
1028 if (!eligible_pid(wo, p))
1029 return 0;
1030
1031 /*
1032 * Wait for all children (clone and not) if __WALL is set or
1033 * if it is traced by us.
1034 */
1035 if (ptrace || (wo->wo_flags & __WALL))
1036 return 1;
1037
1038 /*
1039 * Otherwise, wait for clone children *only* if __WCLONE is set;
1040 * otherwise, wait for non-clone children *only*.
1041 *
1042 * Note: a "clone" child here is one that reports to its parent
1043 * using a signal other than SIGCHLD, or a non-leader thread which
1044 * we can only see if it is traced by us.
1045 */
1046 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1047 return 0;
1048
1049 return 1;
1050 }
1051
1052 static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
1053 pid_t pid, uid_t uid, int why, int status)
1054 {
1055 struct siginfo __user *infop;
1056 int retval = wo->wo_rusage
1057 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1058
1059 put_task_struct(p);
1060 infop = wo->wo_info;
1061 if (infop) {
1062 if (!retval)
1063 retval = put_user(SIGCHLD, &infop->si_signo);
1064 if (!retval)
1065 retval = put_user(0, &infop->si_errno);
1066 if (!retval)
1067 retval = put_user((short)why, &infop->si_code);
1068 if (!retval)
1069 retval = put_user(pid, &infop->si_pid);
1070 if (!retval)
1071 retval = put_user(uid, &infop->si_uid);
1072 if (!retval)
1073 retval = put_user(status, &infop->si_status);
1074 }
1075 if (!retval)
1076 retval = pid;
1077 return retval;
1078 }
1079
1080 /*
1081 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
1082 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1083 * the lock and this task is uninteresting. If we return nonzero, we have
1084 * released the lock and the system call should return.
1085 */
1086 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1087 {
1088 int state, retval, status;
1089 pid_t pid = task_pid_vnr(p);
1090 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1091 struct siginfo __user *infop;
1092
1093 if (!likely(wo->wo_flags & WEXITED))
1094 return 0;
1095
1096 if (unlikely(wo->wo_flags & WNOWAIT)) {
1097 int exit_code = p->exit_code;
1098 int why;
1099
1100 get_task_struct(p);
1101 read_unlock(&tasklist_lock);
1102 sched_annotate_sleep();
1103
1104 if ((exit_code & 0x7f) == 0) {
1105 why = CLD_EXITED;
1106 status = exit_code >> 8;
1107 } else {
1108 why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1109 status = exit_code & 0x7f;
1110 }
1111 return wait_noreap_copyout(wo, p, pid, uid, why, status);
1112 }
1113 /*
1114 * Move the task's state to DEAD/TRACE, only one thread can do this.
1115 */
1116 state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1117 EXIT_TRACE : EXIT_DEAD;
1118 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1119 return 0;
1120 /*
1121 * We own this thread, nobody else can reap it.
1122 */
1123 read_unlock(&tasklist_lock);
1124 sched_annotate_sleep();
1125
1126 /*
1127 * Check thread_group_leader() to exclude the traced sub-threads.
1128 */
1129 if (state == EXIT_DEAD && thread_group_leader(p)) {
1130 struct signal_struct *sig = p->signal;
1131 struct signal_struct *psig = current->signal;
1132 unsigned long maxrss;
1133 u64 tgutime, tgstime;
1134
1135 /*
1136 * The resource counters for the group leader are in its
1137 * own task_struct. Those for dead threads in the group
1138 * are in its signal_struct, as are those for the child
1139 * processes it has previously reaped. All these
1140 * accumulate in the parent's signal_struct c* fields.
1141 *
1142 * We don't bother to take a lock here to protect these
1143 * p->signal fields because the whole thread group is dead
1144 * and nobody can change them.
1145 *
1146 * psig->stats_lock also protects us from our sub-theads
1147 * which can reap other children at the same time. Until
1148 * we change k_getrusage()-like users to rely on this lock
1149 * we have to take ->siglock as well.
1150 *
1151 * We use thread_group_cputime_adjusted() to get times for
1152 * the thread group, which consolidates times for all threads
1153 * in the group including the group leader.
1154 */
1155 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1156 spin_lock_irq(&current->sighand->siglock);
1157 write_seqlock(&psig->stats_lock);
1158 psig->cutime += tgutime + sig->cutime;
1159 psig->cstime += tgstime + sig->cstime;
1160 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1161 psig->cmin_flt +=
1162 p->min_flt + sig->min_flt + sig->cmin_flt;
1163 psig->cmaj_flt +=
1164 p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1165 psig->cnvcsw +=
1166 p->nvcsw + sig->nvcsw + sig->cnvcsw;
1167 psig->cnivcsw +=
1168 p->nivcsw + sig->nivcsw + sig->cnivcsw;
1169 psig->cinblock +=
1170 task_io_get_inblock(p) +
1171 sig->inblock + sig->cinblock;
1172 psig->coublock +=
1173 task_io_get_oublock(p) +
1174 sig->oublock + sig->coublock;
1175 maxrss = max(sig->maxrss, sig->cmaxrss);
1176 if (psig->cmaxrss < maxrss)
1177 psig->cmaxrss = maxrss;
1178 task_io_accounting_add(&psig->ioac, &p->ioac);
1179 task_io_accounting_add(&psig->ioac, &sig->ioac);
1180 write_sequnlock(&psig->stats_lock);
1181 spin_unlock_irq(&current->sighand->siglock);
1182 }
1183
1184 retval = wo->wo_rusage
1185 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1186 status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1187 ? p->signal->group_exit_code : p->exit_code;
1188 if (!retval && wo->wo_stat)
1189 retval = put_user(status, wo->wo_stat);
1190
1191 infop = wo->wo_info;
1192 if (!retval && infop)
1193 retval = put_user(SIGCHLD, &infop->si_signo);
1194 if (!retval && infop)
1195 retval = put_user(0, &infop->si_errno);
1196 if (!retval && infop) {
1197 int why;
1198
1199 if ((status & 0x7f) == 0) {
1200 why = CLD_EXITED;
1201 status >>= 8;
1202 } else {
1203 why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1204 status &= 0x7f;
1205 }
1206 retval = put_user((short)why, &infop->si_code);
1207 if (!retval)
1208 retval = put_user(status, &infop->si_status);
1209 }
1210 if (!retval && infop)
1211 retval = put_user(pid, &infop->si_pid);
1212 if (!retval && infop)
1213 retval = put_user(uid, &infop->si_uid);
1214 if (!retval)
1215 retval = pid;
1216
1217 if (state == EXIT_TRACE) {
1218 write_lock_irq(&tasklist_lock);
1219 /* We dropped tasklist, ptracer could die and untrace */
1220 ptrace_unlink(p);
1221
1222 /* If parent wants a zombie, don't release it now */
1223 state = EXIT_ZOMBIE;
1224 if (do_notify_parent(p, p->exit_signal))
1225 state = EXIT_DEAD;
1226 p->exit_state = state;
1227 write_unlock_irq(&tasklist_lock);
1228 }
1229 if (state == EXIT_DEAD)
1230 release_task(p);
1231
1232 return retval;
1233 }
1234
1235 static int *task_stopped_code(struct task_struct *p, bool ptrace)
1236 {
1237 if (ptrace) {
1238 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1239 return &p->exit_code;
1240 } else {
1241 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1242 return &p->signal->group_exit_code;
1243 }
1244 return NULL;
1245 }
1246
1247 /**
1248 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1249 * @wo: wait options
1250 * @ptrace: is the wait for ptrace
1251 * @p: task to wait for
1252 *
1253 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1254 *
1255 * CONTEXT:
1256 * read_lock(&tasklist_lock), which is released if return value is
1257 * non-zero. Also, grabs and releases @p->sighand->siglock.
1258 *
1259 * RETURNS:
1260 * 0 if wait condition didn't exist and search for other wait conditions
1261 * should continue. Non-zero return, -errno on failure and @p's pid on
1262 * success, implies that tasklist_lock is released and wait condition
1263 * search should terminate.
1264 */
1265 static int wait_task_stopped(struct wait_opts *wo,
1266 int ptrace, struct task_struct *p)
1267 {
1268 struct siginfo __user *infop;
1269 int retval, exit_code, *p_code, why;
1270 uid_t uid = 0; /* unneeded, required by compiler */
1271 pid_t pid;
1272
1273 /*
1274 * Traditionally we see ptrace'd stopped tasks regardless of options.
1275 */
1276 if (!ptrace && !(wo->wo_flags & WUNTRACED))
1277 return 0;
1278
1279 if (!task_stopped_code(p, ptrace))
1280 return 0;
1281
1282 exit_code = 0;
1283 spin_lock_irq(&p->sighand->siglock);
1284
1285 p_code = task_stopped_code(p, ptrace);
1286 if (unlikely(!p_code))
1287 goto unlock_sig;
1288
1289 exit_code = *p_code;
1290 if (!exit_code)
1291 goto unlock_sig;
1292
1293 if (!unlikely(wo->wo_flags & WNOWAIT))
1294 *p_code = 0;
1295
1296 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1297 unlock_sig:
1298 spin_unlock_irq(&p->sighand->siglock);
1299 if (!exit_code)
1300 return 0;
1301
1302 /*
1303 * Now we are pretty sure this task is interesting.
1304 * Make sure it doesn't get reaped out from under us while we
1305 * give up the lock and then examine it below. We don't want to
1306 * keep holding onto the tasklist_lock while we call getrusage and
1307 * possibly take page faults for user memory.
1308 */
1309 get_task_struct(p);
1310 pid = task_pid_vnr(p);
1311 why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1312 read_unlock(&tasklist_lock);
1313 sched_annotate_sleep();
1314
1315 if (unlikely(wo->wo_flags & WNOWAIT))
1316 return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1317
1318 retval = wo->wo_rusage
1319 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1320 if (!retval && wo->wo_stat)
1321 retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1322
1323 infop = wo->wo_info;
1324 if (!retval && infop)
1325 retval = put_user(SIGCHLD, &infop->si_signo);
1326 if (!retval && infop)
1327 retval = put_user(0, &infop->si_errno);
1328 if (!retval && infop)
1329 retval = put_user((short)why, &infop->si_code);
1330 if (!retval && infop)
1331 retval = put_user(exit_code, &infop->si_status);
1332 if (!retval && infop)
1333 retval = put_user(pid, &infop->si_pid);
1334 if (!retval && infop)
1335 retval = put_user(uid, &infop->si_uid);
1336 if (!retval)
1337 retval = pid;
1338 put_task_struct(p);
1339
1340 BUG_ON(!retval);
1341 return retval;
1342 }
1343
1344 /*
1345 * Handle do_wait work for one task in a live, non-stopped state.
1346 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1347 * the lock and this task is uninteresting. If we return nonzero, we have
1348 * released the lock and the system call should return.
1349 */
1350 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1351 {
1352 int retval;
1353 pid_t pid;
1354 uid_t uid;
1355
1356 if (!unlikely(wo->wo_flags & WCONTINUED))
1357 return 0;
1358
1359 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1360 return 0;
1361
1362 spin_lock_irq(&p->sighand->siglock);
1363 /* Re-check with the lock held. */
1364 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1365 spin_unlock_irq(&p->sighand->siglock);
1366 return 0;
1367 }
1368 if (!unlikely(wo->wo_flags & WNOWAIT))
1369 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1370 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1371 spin_unlock_irq(&p->sighand->siglock);
1372
1373 pid = task_pid_vnr(p);
1374 get_task_struct(p);
1375 read_unlock(&tasklist_lock);
1376 sched_annotate_sleep();
1377
1378 if (!wo->wo_info) {
1379 retval = wo->wo_rusage
1380 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1381 put_task_struct(p);
1382 if (!retval && wo->wo_stat)
1383 retval = put_user(0xffff, wo->wo_stat);
1384 if (!retval)
1385 retval = pid;
1386 } else {
1387 retval = wait_noreap_copyout(wo, p, pid, uid,
1388 CLD_CONTINUED, SIGCONT);
1389 BUG_ON(retval == 0);
1390 }
1391
1392 return retval;
1393 }
1394
1395 /*
1396 * Consider @p for a wait by @parent.
1397 *
1398 * -ECHILD should be in ->notask_error before the first call.
1399 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1400 * Returns zero if the search for a child should continue;
1401 * then ->notask_error is 0 if @p is an eligible child,
1402 * or still -ECHILD.
1403 */
1404 static int wait_consider_task(struct wait_opts *wo, int ptrace,
1405 struct task_struct *p)
1406 {
1407 /*
1408 * We can race with wait_task_zombie() from another thread.
1409 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1410 * can't confuse the checks below.
1411 */
1412 int exit_state = ACCESS_ONCE(p->exit_state);
1413 int ret;
1414
1415 if (unlikely(exit_state == EXIT_DEAD))
1416 return 0;
1417
1418 ret = eligible_child(wo, ptrace, p);
1419 if (!ret)
1420 return ret;
1421
1422 if (unlikely(exit_state == EXIT_TRACE)) {
1423 /*
1424 * ptrace == 0 means we are the natural parent. In this case
1425 * we should clear notask_error, debugger will notify us.
1426 */
1427 if (likely(!ptrace))
1428 wo->notask_error = 0;
1429 return 0;
1430 }
1431
1432 if (likely(!ptrace) && unlikely(p->ptrace)) {
1433 /*
1434 * If it is traced by its real parent's group, just pretend
1435 * the caller is ptrace_do_wait() and reap this child if it
1436 * is zombie.
1437 *
1438 * This also hides group stop state from real parent; otherwise
1439 * a single stop can be reported twice as group and ptrace stop.
1440 * If a ptracer wants to distinguish these two events for its
1441 * own children it should create a separate process which takes
1442 * the role of real parent.
1443 */
1444 if (!ptrace_reparented(p))
1445 ptrace = 1;
1446 }
1447
1448 /* slay zombie? */
1449 if (exit_state == EXIT_ZOMBIE) {
1450 /* we don't reap group leaders with subthreads */
1451 if (!delay_group_leader(p)) {
1452 /*
1453 * A zombie ptracee is only visible to its ptracer.
1454 * Notification and reaping will be cascaded to the
1455 * real parent when the ptracer detaches.
1456 */
1457 if (unlikely(ptrace) || likely(!p->ptrace))
1458 return wait_task_zombie(wo, p);
1459 }
1460
1461 /*
1462 * Allow access to stopped/continued state via zombie by
1463 * falling through. Clearing of notask_error is complex.
1464 *
1465 * When !@ptrace:
1466 *
1467 * If WEXITED is set, notask_error should naturally be
1468 * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1469 * so, if there are live subthreads, there are events to
1470 * wait for. If all subthreads are dead, it's still safe
1471 * to clear - this function will be called again in finite
1472 * amount time once all the subthreads are released and
1473 * will then return without clearing.
1474 *
1475 * When @ptrace:
1476 *
1477 * Stopped state is per-task and thus can't change once the
1478 * target task dies. Only continued and exited can happen.
1479 * Clear notask_error if WCONTINUED | WEXITED.
1480 */
1481 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1482 wo->notask_error = 0;
1483 } else {
1484 /*
1485 * @p is alive and it's gonna stop, continue or exit, so
1486 * there always is something to wait for.
1487 */
1488 wo->notask_error = 0;
1489 }
1490
1491 /*
1492 * Wait for stopped. Depending on @ptrace, different stopped state
1493 * is used and the two don't interact with each other.
1494 */
1495 ret = wait_task_stopped(wo, ptrace, p);
1496 if (ret)
1497 return ret;
1498
1499 /*
1500 * Wait for continued. There's only one continued state and the
1501 * ptracer can consume it which can confuse the real parent. Don't
1502 * use WCONTINUED from ptracer. You don't need or want it.
1503 */
1504 return wait_task_continued(wo, p);
1505 }
1506
1507 /*
1508 * Do the work of do_wait() for one thread in the group, @tsk.
1509 *
1510 * -ECHILD should be in ->notask_error before the first call.
1511 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1512 * Returns zero if the search for a child should continue; then
1513 * ->notask_error is 0 if there were any eligible children,
1514 * or still -ECHILD.
1515 */
1516 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1517 {
1518 struct task_struct *p;
1519
1520 list_for_each_entry(p, &tsk->children, sibling) {
1521 int ret = wait_consider_task(wo, 0, p);
1522
1523 if (ret)
1524 return ret;
1525 }
1526
1527 return 0;
1528 }
1529
1530 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1531 {
1532 struct task_struct *p;
1533
1534 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1535 int ret = wait_consider_task(wo, 1, p);
1536
1537 if (ret)
1538 return ret;
1539 }
1540
1541 return 0;
1542 }
1543
1544 static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1545 int sync, void *key)
1546 {
1547 struct wait_opts *wo = container_of(wait, struct wait_opts,
1548 child_wait);
1549 struct task_struct *p = key;
1550
1551 if (!eligible_pid(wo, p))
1552 return 0;
1553
1554 if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1555 return 0;
1556
1557 return default_wake_function(wait, mode, sync, key);
1558 }
1559
1560 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1561 {
1562 __wake_up_sync_key(&parent->signal->wait_chldexit,
1563 TASK_INTERRUPTIBLE, 1, p);
1564 }
1565
1566 static long do_wait(struct wait_opts *wo)
1567 {
1568 struct task_struct *tsk;
1569 int retval;
1570
1571 trace_sched_process_wait(wo->wo_pid);
1572
1573 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1574 wo->child_wait.private = current;
1575 add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1576 repeat:
1577 /*
1578 * If there is nothing that can match our criteria, just get out.
1579 * We will clear ->notask_error to zero if we see any child that
1580 * might later match our criteria, even if we are not able to reap
1581 * it yet.
1582 */
1583 wo->notask_error = -ECHILD;
1584 if ((wo->wo_type < PIDTYPE_MAX) &&
1585 (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1586 goto notask;
1587
1588 set_current_state(TASK_INTERRUPTIBLE);
1589 read_lock(&tasklist_lock);
1590 tsk = current;
1591 do {
1592 retval = do_wait_thread(wo, tsk);
1593 if (retval)
1594 goto end;
1595
1596 retval = ptrace_do_wait(wo, tsk);
1597 if (retval)
1598 goto end;
1599
1600 if (wo->wo_flags & __WNOTHREAD)
1601 break;
1602 } while_each_thread(current, tsk);
1603 read_unlock(&tasklist_lock);
1604
1605 notask:
1606 retval = wo->notask_error;
1607 if (!retval && !(wo->wo_flags & WNOHANG)) {
1608 retval = -ERESTARTSYS;
1609 if (!signal_pending(current)) {
1610 schedule();
1611 goto repeat;
1612 }
1613 }
1614 end:
1615 __set_current_state(TASK_RUNNING);
1616 remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1617 return retval;
1618 }
1619
1620 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1621 infop, int, options, struct rusage __user *, ru)
1622 {
1623 struct wait_opts wo;
1624 struct pid *pid = NULL;
1625 enum pid_type type;
1626 long ret;
1627
1628 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1629 __WNOTHREAD|__WCLONE|__WALL))
1630 return -EINVAL;
1631 if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1632 return -EINVAL;
1633
1634 switch (which) {
1635 case P_ALL:
1636 type = PIDTYPE_MAX;
1637 break;
1638 case P_PID:
1639 type = PIDTYPE_PID;
1640 if (upid <= 0)
1641 return -EINVAL;
1642 break;
1643 case P_PGID:
1644 type = PIDTYPE_PGID;
1645 if (upid <= 0)
1646 return -EINVAL;
1647 break;
1648 default:
1649 return -EINVAL;
1650 }
1651
1652 if (type < PIDTYPE_MAX)
1653 pid = find_get_pid(upid);
1654
1655 wo.wo_type = type;
1656 wo.wo_pid = pid;
1657 wo.wo_flags = options;
1658 wo.wo_info = infop;
1659 wo.wo_stat = NULL;
1660 wo.wo_rusage = ru;
1661 ret = do_wait(&wo);
1662
1663 if (ret > 0) {
1664 ret = 0;
1665 } else if (infop) {
1666 /*
1667 * For a WNOHANG return, clear out all the fields
1668 * we would set so the user can easily tell the
1669 * difference.
1670 */
1671 if (!ret)
1672 ret = put_user(0, &infop->si_signo);
1673 if (!ret)
1674 ret = put_user(0, &infop->si_errno);
1675 if (!ret)
1676 ret = put_user(0, &infop->si_code);
1677 if (!ret)
1678 ret = put_user(0, &infop->si_pid);
1679 if (!ret)
1680 ret = put_user(0, &infop->si_uid);
1681 if (!ret)
1682 ret = put_user(0, &infop->si_status);
1683 }
1684
1685 put_pid(pid);
1686 return ret;
1687 }
1688
1689 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1690 int, options, struct rusage __user *, ru)
1691 {
1692 struct wait_opts wo;
1693 struct pid *pid = NULL;
1694 enum pid_type type;
1695 long ret;
1696
1697 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1698 __WNOTHREAD|__WCLONE|__WALL))
1699 return -EINVAL;
1700
1701 if (upid == -1)
1702 type = PIDTYPE_MAX;
1703 else if (upid < 0) {
1704 type = PIDTYPE_PGID;
1705 pid = find_get_pid(-upid);
1706 } else if (upid == 0) {
1707 type = PIDTYPE_PGID;
1708 pid = get_task_pid(current, PIDTYPE_PGID);
1709 } else /* upid > 0 */ {
1710 type = PIDTYPE_PID;
1711 pid = find_get_pid(upid);
1712 }
1713
1714 wo.wo_type = type;
1715 wo.wo_pid = pid;
1716 wo.wo_flags = options | WEXITED;
1717 wo.wo_info = NULL;
1718 wo.wo_stat = stat_addr;
1719 wo.wo_rusage = ru;
1720 ret = do_wait(&wo);
1721 put_pid(pid);
1722
1723 return ret;
1724 }
1725
1726 #ifdef __ARCH_WANT_SYS_WAITPID
1727
1728 /*
1729 * sys_waitpid() remains for compatibility. waitpid() should be
1730 * implemented by calling sys_wait4() from libc.a.
1731 */
1732 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1733 {
1734 return sys_wait4(pid, stat_addr, options, NULL);
1735 }
1736
1737 #endif