Root/kernel/exit.c

1/*
2 * linux/kernel/exit.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7#include <linux/mm.h>
8#include <linux/slab.h>
9#include <linux/interrupt.h>
10#include <linux/module.h>
11#include <linux/capability.h>
12#include <linux/completion.h>
13#include <linux/personality.h>
14#include <linux/tty.h>
15#include <linux/iocontext.h>
16#include <linux/key.h>
17#include <linux/security.h>
18#include <linux/cpu.h>
19#include <linux/acct.h>
20#include <linux/tsacct_kern.h>
21#include <linux/file.h>
22#include <linux/fdtable.h>
23#include <linux/freezer.h>
24#include <linux/binfmts.h>
25#include <linux/nsproxy.h>
26#include <linux/pid_namespace.h>
27#include <linux/ptrace.h>
28#include <linux/profile.h>
29#include <linux/mount.h>
30#include <linux/proc_fs.h>
31#include <linux/kthread.h>
32#include <linux/mempolicy.h>
33#include <linux/taskstats_kern.h>
34#include <linux/delayacct.h>
35#include <linux/cgroup.h>
36#include <linux/syscalls.h>
37#include <linux/signal.h>
38#include <linux/posix-timers.h>
39#include <linux/cn_proc.h>
40#include <linux/mutex.h>
41#include <linux/futex.h>
42#include <linux/pipe_fs_i.h>
43#include <linux/audit.h> /* for audit_free() */
44#include <linux/resource.h>
45#include <linux/blkdev.h>
46#include <linux/task_io_accounting_ops.h>
47#include <linux/tracehook.h>
48#include <linux/fs_struct.h>
49#include <linux/init_task.h>
50#include <linux/perf_event.h>
51#include <trace/events/sched.h>
52#include <linux/hw_breakpoint.h>
53#include <linux/oom.h>
54#include <linux/writeback.h>
55#include <linux/shm.h>
56
57#include <asm/uaccess.h>
58#include <asm/unistd.h>
59#include <asm/pgtable.h>
60#include <asm/mmu_context.h>
61
62static void exit_mm(struct task_struct * tsk);
63
64static void __unhash_process(struct task_struct *p, bool group_dead)
65{
66    nr_threads--;
67    detach_pid(p, PIDTYPE_PID);
68    if (group_dead) {
69        detach_pid(p, PIDTYPE_PGID);
70        detach_pid(p, PIDTYPE_SID);
71
72        list_del_rcu(&p->tasks);
73        list_del_init(&p->sibling);
74        __this_cpu_dec(process_counts);
75    }
76    list_del_rcu(&p->thread_group);
77    list_del_rcu(&p->thread_node);
78}
79
80/*
81 * This function expects the tasklist_lock write-locked.
82 */
83static void __exit_signal(struct task_struct *tsk)
84{
85    struct signal_struct *sig = tsk->signal;
86    bool group_dead = thread_group_leader(tsk);
87    struct sighand_struct *sighand;
88    struct tty_struct *uninitialized_var(tty);
89    cputime_t utime, stime;
90
91    sighand = rcu_dereference_check(tsk->sighand,
92                    lockdep_tasklist_lock_is_held());
93    spin_lock(&sighand->siglock);
94
95    posix_cpu_timers_exit(tsk);
96    if (group_dead) {
97        posix_cpu_timers_exit_group(tsk);
98        tty = sig->tty;
99        sig->tty = NULL;
100    } else {
101        /*
102         * This can only happen if the caller is de_thread().
103         * FIXME: this is the temporary hack, we should teach
104         * posix-cpu-timers to handle this case correctly.
105         */
106        if (unlikely(has_group_leader_pid(tsk)))
107            posix_cpu_timers_exit_group(tsk);
108
109        /*
110         * If there is any task waiting for the group exit
111         * then notify it:
112         */
113        if (sig->notify_count > 0 && !--sig->notify_count)
114            wake_up_process(sig->group_exit_task);
115
116        if (tsk == sig->curr_target)
117            sig->curr_target = next_thread(tsk);
118        /*
119         * Accumulate here the counters for all threads but the
120         * group leader as they die, so they can be added into
121         * the process-wide totals when those are taken.
122         * The group leader stays around as a zombie as long
123         * as there are other threads. When it gets reaped,
124         * the exit.c code will add its counts into these totals.
125         * We won't ever get here for the group leader, since it
126         * will have been the last reference on the signal_struct.
127         */
128        task_cputime(tsk, &utime, &stime);
129        sig->utime += utime;
130        sig->stime += stime;
131        sig->gtime += task_gtime(tsk);
132        sig->min_flt += tsk->min_flt;
133        sig->maj_flt += tsk->maj_flt;
134        sig->nvcsw += tsk->nvcsw;
135        sig->nivcsw += tsk->nivcsw;
136        sig->inblock += task_io_get_inblock(tsk);
137        sig->oublock += task_io_get_oublock(tsk);
138        task_io_accounting_add(&sig->ioac, &tsk->ioac);
139        sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
140    }
141
142    sig->nr_threads--;
143    __unhash_process(tsk, group_dead);
144
145    /*
146     * Do this under ->siglock, we can race with another thread
147     * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
148     */
149    flush_sigqueue(&tsk->pending);
150    tsk->sighand = NULL;
151    spin_unlock(&sighand->siglock);
152
153    __cleanup_sighand(sighand);
154    clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
155    if (group_dead) {
156        flush_sigqueue(&sig->shared_pending);
157        tty_kref_put(tty);
158    }
159}
160
161static void delayed_put_task_struct(struct rcu_head *rhp)
162{
163    struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
164
165    perf_event_delayed_put(tsk);
166    trace_sched_process_free(tsk);
167    put_task_struct(tsk);
168}
169
170
171void release_task(struct task_struct * p)
172{
173    struct task_struct *leader;
174    int zap_leader;
175repeat:
176    /* don't need to get the RCU readlock here - the process is dead and
177     * can't be modifying its own credentials. But shut RCU-lockdep up */
178    rcu_read_lock();
179    atomic_dec(&__task_cred(p)->user->processes);
180    rcu_read_unlock();
181
182    proc_flush_task(p);
183
184    write_lock_irq(&tasklist_lock);
185    ptrace_release_task(p);
186    __exit_signal(p);
187
188    /*
189     * If we are the last non-leader member of the thread
190     * group, and the leader is zombie, then notify the
191     * group leader's parent process. (if it wants notification.)
192     */
193    zap_leader = 0;
194    leader = p->group_leader;
195    if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
196        /*
197         * If we were the last child thread and the leader has
198         * exited already, and the leader's parent ignores SIGCHLD,
199         * then we are the one who should release the leader.
200         */
201        zap_leader = do_notify_parent(leader, leader->exit_signal);
202        if (zap_leader)
203            leader->exit_state = EXIT_DEAD;
204    }
205
206    write_unlock_irq(&tasklist_lock);
207    release_thread(p);
208    call_rcu(&p->rcu, delayed_put_task_struct);
209
210    p = leader;
211    if (unlikely(zap_leader))
212        goto repeat;
213}
214
215/*
216 * This checks not only the pgrp, but falls back on the pid if no
217 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
218 * without this...
219 *
220 * The caller must hold rcu lock or the tasklist lock.
221 */
222struct pid *session_of_pgrp(struct pid *pgrp)
223{
224    struct task_struct *p;
225    struct pid *sid = NULL;
226
227    p = pid_task(pgrp, PIDTYPE_PGID);
228    if (p == NULL)
229        p = pid_task(pgrp, PIDTYPE_PID);
230    if (p != NULL)
231        sid = task_session(p);
232
233    return sid;
234}
235
236/*
237 * Determine if a process group is "orphaned", according to the POSIX
238 * definition in 2.2.2.52. Orphaned process groups are not to be affected
239 * by terminal-generated stop signals. Newly orphaned process groups are
240 * to receive a SIGHUP and a SIGCONT.
241 *
242 * "I ask you, have you ever known what it is to be an orphan?"
243 */
244static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
245{
246    struct task_struct *p;
247
248    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
249        if ((p == ignored_task) ||
250            (p->exit_state && thread_group_empty(p)) ||
251            is_global_init(p->real_parent))
252            continue;
253
254        if (task_pgrp(p->real_parent) != pgrp &&
255            task_session(p->real_parent) == task_session(p))
256            return 0;
257    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
258
259    return 1;
260}
261
262int is_current_pgrp_orphaned(void)
263{
264    int retval;
265
266    read_lock(&tasklist_lock);
267    retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
268    read_unlock(&tasklist_lock);
269
270    return retval;
271}
272
273static bool has_stopped_jobs(struct pid *pgrp)
274{
275    struct task_struct *p;
276
277    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
278        if (p->signal->flags & SIGNAL_STOP_STOPPED)
279            return true;
280    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
281
282    return false;
283}
284
285/*
286 * Check to see if any process groups have become orphaned as
287 * a result of our exiting, and if they have any stopped jobs,
288 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
289 */
290static void
291kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
292{
293    struct pid *pgrp = task_pgrp(tsk);
294    struct task_struct *ignored_task = tsk;
295
296    if (!parent)
297         /* exit: our father is in a different pgrp than
298          * we are and we were the only connection outside.
299          */
300        parent = tsk->real_parent;
301    else
302        /* reparent: our child is in a different pgrp than
303         * we are, and it was the only connection outside.
304         */
305        ignored_task = NULL;
306
307    if (task_pgrp(parent) != pgrp &&
308        task_session(parent) == task_session(tsk) &&
309        will_become_orphaned_pgrp(pgrp, ignored_task) &&
310        has_stopped_jobs(pgrp)) {
311        __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
312        __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
313    }
314}
315
316/*
317 * Let kernel threads use this to say that they allow a certain signal.
318 * Must not be used if kthread was cloned with CLONE_SIGHAND.
319 */
320int allow_signal(int sig)
321{
322    if (!valid_signal(sig) || sig < 1)
323        return -EINVAL;
324
325    spin_lock_irq(&current->sighand->siglock);
326    /* This is only needed for daemonize()'ed kthreads */
327    sigdelset(&current->blocked, sig);
328    /*
329     * Kernel threads handle their own signals. Let the signal code
330     * know it'll be handled, so that they don't get converted to
331     * SIGKILL or just silently dropped.
332     */
333    current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
334    recalc_sigpending();
335    spin_unlock_irq(&current->sighand->siglock);
336    return 0;
337}
338
339EXPORT_SYMBOL(allow_signal);
340
341int disallow_signal(int sig)
342{
343    if (!valid_signal(sig) || sig < 1)
344        return -EINVAL;
345
346    spin_lock_irq(&current->sighand->siglock);
347    current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
348    recalc_sigpending();
349    spin_unlock_irq(&current->sighand->siglock);
350    return 0;
351}
352
353EXPORT_SYMBOL(disallow_signal);
354
355#ifdef CONFIG_MM_OWNER
356/*
357 * A task is exiting. If it owned this mm, find a new owner for the mm.
358 */
359void mm_update_next_owner(struct mm_struct *mm)
360{
361    struct task_struct *c, *g, *p = current;
362
363retry:
364    /*
365     * If the exiting or execing task is not the owner, it's
366     * someone else's problem.
367     */
368    if (mm->owner != p)
369        return;
370    /*
371     * The current owner is exiting/execing and there are no other
372     * candidates. Do not leave the mm pointing to a possibly
373     * freed task structure.
374     */
375    if (atomic_read(&mm->mm_users) <= 1) {
376        mm->owner = NULL;
377        return;
378    }
379
380    read_lock(&tasklist_lock);
381    /*
382     * Search in the children
383     */
384    list_for_each_entry(c, &p->children, sibling) {
385        if (c->mm == mm)
386            goto assign_new_owner;
387    }
388
389    /*
390     * Search in the siblings
391     */
392    list_for_each_entry(c, &p->real_parent->children, sibling) {
393        if (c->mm == mm)
394            goto assign_new_owner;
395    }
396
397    /*
398     * Search through everything else. We should not get
399     * here often
400     */
401    do_each_thread(g, c) {
402        if (c->mm == mm)
403            goto assign_new_owner;
404    } while_each_thread(g, c);
405
406    read_unlock(&tasklist_lock);
407    /*
408     * We found no owner yet mm_users > 1: this implies that we are
409     * most likely racing with swapoff (try_to_unuse()) or /proc or
410     * ptrace or page migration (get_task_mm()). Mark owner as NULL.
411     */
412    mm->owner = NULL;
413    return;
414
415assign_new_owner:
416    BUG_ON(c == p);
417    get_task_struct(c);
418    /*
419     * The task_lock protects c->mm from changing.
420     * We always want mm->owner->mm == mm
421     */
422    task_lock(c);
423    /*
424     * Delay read_unlock() till we have the task_lock()
425     * to ensure that c does not slip away underneath us
426     */
427    read_unlock(&tasklist_lock);
428    if (c->mm != mm) {
429        task_unlock(c);
430        put_task_struct(c);
431        goto retry;
432    }
433    mm->owner = c;
434    task_unlock(c);
435    put_task_struct(c);
436}
437#endif /* CONFIG_MM_OWNER */
438
439/*
440 * Turn us into a lazy TLB process if we
441 * aren't already..
442 */
443static void exit_mm(struct task_struct * tsk)
444{
445    struct mm_struct *mm = tsk->mm;
446    struct core_state *core_state;
447
448    mm_release(tsk, mm);
449    if (!mm)
450        return;
451    sync_mm_rss(mm);
452    /*
453     * Serialize with any possible pending coredump.
454     * We must hold mmap_sem around checking core_state
455     * and clearing tsk->mm. The core-inducing thread
456     * will increment ->nr_threads for each thread in the
457     * group with ->mm != NULL.
458     */
459    down_read(&mm->mmap_sem);
460    core_state = mm->core_state;
461    if (core_state) {
462        struct core_thread self;
463        up_read(&mm->mmap_sem);
464
465        self.task = tsk;
466        self.next = xchg(&core_state->dumper.next, &self);
467        /*
468         * Implies mb(), the result of xchg() must be visible
469         * to core_state->dumper.
470         */
471        if (atomic_dec_and_test(&core_state->nr_threads))
472            complete(&core_state->startup);
473
474        for (;;) {
475            set_task_state(tsk, TASK_UNINTERRUPTIBLE);
476            if (!self.task) /* see coredump_finish() */
477                break;
478            freezable_schedule();
479        }
480        __set_task_state(tsk, TASK_RUNNING);
481        down_read(&mm->mmap_sem);
482    }
483    atomic_inc(&mm->mm_count);
484    BUG_ON(mm != tsk->active_mm);
485    /* more a memory barrier than a real lock */
486    task_lock(tsk);
487    tsk->mm = NULL;
488    up_read(&mm->mmap_sem);
489    enter_lazy_tlb(mm, current);
490    task_unlock(tsk);
491    mm_update_next_owner(mm);
492    mmput(mm);
493}
494
495/*
496 * When we die, we re-parent all our children, and try to:
497 * 1. give them to another thread in our thread group, if such a member exists
498 * 2. give it to the first ancestor process which prctl'd itself as a
499 * child_subreaper for its children (like a service manager)
500 * 3. give it to the init process (PID 1) in our pid namespace
501 */
502static struct task_struct *find_new_reaper(struct task_struct *father)
503    __releases(&tasklist_lock)
504    __acquires(&tasklist_lock)
505{
506    struct pid_namespace *pid_ns = task_active_pid_ns(father);
507    struct task_struct *thread;
508
509    thread = father;
510    while_each_thread(father, thread) {
511        if (thread->flags & PF_EXITING)
512            continue;
513        if (unlikely(pid_ns->child_reaper == father))
514            pid_ns->child_reaper = thread;
515        return thread;
516    }
517
518    if (unlikely(pid_ns->child_reaper == father)) {
519        write_unlock_irq(&tasklist_lock);
520        if (unlikely(pid_ns == &init_pid_ns)) {
521            panic("Attempted to kill init! exitcode=0x%08x\n",
522                father->signal->group_exit_code ?:
523                    father->exit_code);
524        }
525
526        zap_pid_ns_processes(pid_ns);
527        write_lock_irq(&tasklist_lock);
528    } else if (father->signal->has_child_subreaper) {
529        struct task_struct *reaper;
530
531        /*
532         * Find the first ancestor marked as child_subreaper.
533         * Note that the code below checks same_thread_group(reaper,
534         * pid_ns->child_reaper). This is what we need to DTRT in a
535         * PID namespace. However we still need the check above, see
536         * http://marc.info/?l=linux-kernel&m=131385460420380
537         */
538        for (reaper = father->real_parent;
539             reaper != &init_task;
540             reaper = reaper->real_parent) {
541            if (same_thread_group(reaper, pid_ns->child_reaper))
542                break;
543            if (!reaper->signal->is_child_subreaper)
544                continue;
545            thread = reaper;
546            do {
547                if (!(thread->flags & PF_EXITING))
548                    return reaper;
549            } while_each_thread(reaper, thread);
550        }
551    }
552
553    return pid_ns->child_reaper;
554}
555
556/*
557* Any that need to be release_task'd are put on the @dead list.
558 */
559static void reparent_leader(struct task_struct *father, struct task_struct *p,
560                struct list_head *dead)
561{
562    list_move_tail(&p->sibling, &p->real_parent->children);
563
564    if (p->exit_state == EXIT_DEAD)
565        return;
566    /*
567     * If this is a threaded reparent there is no need to
568     * notify anyone anything has happened.
569     */
570    if (same_thread_group(p->real_parent, father))
571        return;
572
573    /* We don't want people slaying init. */
574    p->exit_signal = SIGCHLD;
575
576    /* If it has exited notify the new parent about this child's death. */
577    if (!p->ptrace &&
578        p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
579        if (do_notify_parent(p, p->exit_signal)) {
580            p->exit_state = EXIT_DEAD;
581            list_move_tail(&p->sibling, dead);
582        }
583    }
584
585    kill_orphaned_pgrp(p, father);
586}
587
588static void forget_original_parent(struct task_struct *father)
589{
590    struct task_struct *p, *n, *reaper;
591    LIST_HEAD(dead_children);
592
593    write_lock_irq(&tasklist_lock);
594    /*
595     * Note that exit_ptrace() and find_new_reaper() might
596     * drop tasklist_lock and reacquire it.
597     */
598    exit_ptrace(father);
599    reaper = find_new_reaper(father);
600
601    list_for_each_entry_safe(p, n, &father->children, sibling) {
602        struct task_struct *t = p;
603        do {
604            t->real_parent = reaper;
605            if (t->parent == father) {
606                BUG_ON(t->ptrace);
607                t->parent = t->real_parent;
608            }
609            if (t->pdeath_signal)
610                group_send_sig_info(t->pdeath_signal,
611                            SEND_SIG_NOINFO, t);
612        } while_each_thread(p, t);
613        reparent_leader(father, p, &dead_children);
614    }
615    write_unlock_irq(&tasklist_lock);
616
617    BUG_ON(!list_empty(&father->children));
618
619    list_for_each_entry_safe(p, n, &dead_children, sibling) {
620        list_del_init(&p->sibling);
621        release_task(p);
622    }
623}
624
625/*
626 * Send signals to all our closest relatives so that they know
627 * to properly mourn us..
628 */
629static void exit_notify(struct task_struct *tsk, int group_dead)
630{
631    bool autoreap;
632
633    /*
634     * This does two things:
635     *
636       * A. Make init inherit all the child processes
637     * B. Check to see if any process groups have become orphaned
638     * as a result of our exiting, and if they have any stopped
639     * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
640     */
641    forget_original_parent(tsk);
642
643    write_lock_irq(&tasklist_lock);
644    if (group_dead)
645        kill_orphaned_pgrp(tsk->group_leader, NULL);
646
647    if (unlikely(tsk->ptrace)) {
648        int sig = thread_group_leader(tsk) &&
649                thread_group_empty(tsk) &&
650                !ptrace_reparented(tsk) ?
651            tsk->exit_signal : SIGCHLD;
652        autoreap = do_notify_parent(tsk, sig);
653    } else if (thread_group_leader(tsk)) {
654        autoreap = thread_group_empty(tsk) &&
655            do_notify_parent(tsk, tsk->exit_signal);
656    } else {
657        autoreap = true;
658    }
659
660    tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
661
662    /* mt-exec, de_thread() is waiting for group leader */
663    if (unlikely(tsk->signal->notify_count < 0))
664        wake_up_process(tsk->signal->group_exit_task);
665    write_unlock_irq(&tasklist_lock);
666
667    /* If the process is dead, release it - nobody will wait for it */
668    if (autoreap)
669        release_task(tsk);
670}
671
672#ifdef CONFIG_DEBUG_STACK_USAGE
673static void check_stack_usage(void)
674{
675    static DEFINE_SPINLOCK(low_water_lock);
676    static int lowest_to_date = THREAD_SIZE;
677    unsigned long free;
678
679    free = stack_not_used(current);
680
681    if (free >= lowest_to_date)
682        return;
683
684    spin_lock(&low_water_lock);
685    if (free < lowest_to_date) {
686        printk(KERN_WARNING "%s (%d) used greatest stack depth: "
687                "%lu bytes left\n",
688                current->comm, task_pid_nr(current), free);
689        lowest_to_date = free;
690    }
691    spin_unlock(&low_water_lock);
692}
693#else
694static inline void check_stack_usage(void) {}
695#endif
696
697void do_exit(long code)
698{
699    struct task_struct *tsk = current;
700    int group_dead;
701
702    profile_task_exit(tsk);
703
704    WARN_ON(blk_needs_flush_plug(tsk));
705
706    if (unlikely(in_interrupt()))
707        panic("Aiee, killing interrupt handler!");
708    if (unlikely(!tsk->pid))
709        panic("Attempted to kill the idle task!");
710
711    /*
712     * If do_exit is called because this processes oopsed, it's possible
713     * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
714     * continuing. Amongst other possible reasons, this is to prevent
715     * mm_release()->clear_child_tid() from writing to a user-controlled
716     * kernel address.
717     */
718    set_fs(USER_DS);
719
720    ptrace_event(PTRACE_EVENT_EXIT, code);
721
722    validate_creds_for_do_exit(tsk);
723
724    /*
725     * We're taking recursive faults here in do_exit. Safest is to just
726     * leave this task alone and wait for reboot.
727     */
728    if (unlikely(tsk->flags & PF_EXITING)) {
729        printk(KERN_ALERT
730            "Fixing recursive fault but reboot is needed!\n");
731        /*
732         * We can do this unlocked here. The futex code uses
733         * this flag just to verify whether the pi state
734         * cleanup has been done or not. In the worst case it
735         * loops once more. We pretend that the cleanup was
736         * done as there is no way to return. Either the
737         * OWNER_DIED bit is set by now or we push the blocked
738         * task into the wait for ever nirwana as well.
739         */
740        tsk->flags |= PF_EXITPIDONE;
741        set_current_state(TASK_UNINTERRUPTIBLE);
742        schedule();
743    }
744
745    exit_signals(tsk); /* sets PF_EXITING */
746    /*
747     * tsk->flags are checked in the futex code to protect against
748     * an exiting task cleaning up the robust pi futexes.
749     */
750    smp_mb();
751    raw_spin_unlock_wait(&tsk->pi_lock);
752
753    if (unlikely(in_atomic()))
754        printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
755                current->comm, task_pid_nr(current),
756                preempt_count());
757
758    acct_update_integrals(tsk);
759    /* sync mm's RSS info before statistics gathering */
760    if (tsk->mm)
761        sync_mm_rss(tsk->mm);
762    group_dead = atomic_dec_and_test(&tsk->signal->live);
763    if (group_dead) {
764        hrtimer_cancel(&tsk->signal->real_timer);
765        exit_itimers(tsk->signal);
766        if (tsk->mm)
767            setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
768    }
769    acct_collect(code, group_dead);
770    if (group_dead)
771        tty_audit_exit();
772    audit_free(tsk);
773
774    tsk->exit_code = code;
775    taskstats_exit(tsk, group_dead);
776
777    exit_mm(tsk);
778
779    if (group_dead)
780        acct_process();
781    trace_sched_process_exit(tsk);
782
783    exit_sem(tsk);
784    exit_shm(tsk);
785    exit_files(tsk);
786    exit_fs(tsk);
787    if (group_dead)
788        disassociate_ctty(1);
789    exit_task_namespaces(tsk);
790    exit_task_work(tsk);
791    exit_thread();
792
793    /*
794     * Flush inherited counters to the parent - before the parent
795     * gets woken up by child-exit notifications.
796     *
797     * because of cgroup mode, must be called before cgroup_exit()
798     */
799    perf_event_exit_task(tsk);
800
801    cgroup_exit(tsk);
802
803    module_put(task_thread_info(tsk)->exec_domain->module);
804
805    /*
806     * FIXME: do that only when needed, using sched_exit tracepoint
807     */
808    flush_ptrace_hw_breakpoint(tsk);
809
810    exit_notify(tsk, group_dead);
811    proc_exit_connector(tsk);
812#ifdef CONFIG_NUMA
813    task_lock(tsk);
814    mpol_put(tsk->mempolicy);
815    tsk->mempolicy = NULL;
816    task_unlock(tsk);
817#endif
818#ifdef CONFIG_FUTEX
819    if (unlikely(current->pi_state_cache))
820        kfree(current->pi_state_cache);
821#endif
822    /*
823     * Make sure we are holding no locks:
824     */
825    debug_check_no_locks_held();
826    /*
827     * We can do this unlocked here. The futex code uses this flag
828     * just to verify whether the pi state cleanup has been done
829     * or not. In the worst case it loops once more.
830     */
831    tsk->flags |= PF_EXITPIDONE;
832
833    if (tsk->io_context)
834        exit_io_context(tsk);
835
836    if (tsk->splice_pipe)
837        free_pipe_info(tsk->splice_pipe);
838
839    if (tsk->task_frag.page)
840        put_page(tsk->task_frag.page);
841
842    validate_creds_for_do_exit(tsk);
843
844    check_stack_usage();
845    preempt_disable();
846    if (tsk->nr_dirtied)
847        __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
848    exit_rcu();
849
850    /*
851     * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
852     * when the following two conditions become true.
853     * - There is race condition of mmap_sem (It is acquired by
854     * exit_mm()), and
855     * - SMI occurs before setting TASK_RUNINNG.
856     * (or hypervisor of virtual machine switches to other guest)
857     * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
858     *
859     * To avoid it, we have to wait for releasing tsk->pi_lock which
860     * is held by try_to_wake_up()
861     */
862    smp_mb();
863    raw_spin_unlock_wait(&tsk->pi_lock);
864
865    /* causes final put_task_struct in finish_task_switch(). */
866    tsk->state = TASK_DEAD;
867    tsk->flags |= PF_NOFREEZE; /* tell freezer to ignore us */
868    schedule();
869    BUG();
870    /* Avoid "noreturn function does return". */
871    for (;;)
872        cpu_relax(); /* For when BUG is null */
873}
874
875EXPORT_SYMBOL_GPL(do_exit);
876
877void complete_and_exit(struct completion *comp, long code)
878{
879    if (comp)
880        complete(comp);
881
882    do_exit(code);
883}
884
885EXPORT_SYMBOL(complete_and_exit);
886
887SYSCALL_DEFINE1(exit, int, error_code)
888{
889    do_exit((error_code&0xff)<<8);
890}
891
892/*
893 * Take down every thread in the group. This is called by fatal signals
894 * as well as by sys_exit_group (below).
895 */
896void
897do_group_exit(int exit_code)
898{
899    struct signal_struct *sig = current->signal;
900
901    BUG_ON(exit_code & 0x80); /* core dumps don't get here */
902
903    if (signal_group_exit(sig))
904        exit_code = sig->group_exit_code;
905    else if (!thread_group_empty(current)) {
906        struct sighand_struct *const sighand = current->sighand;
907        spin_lock_irq(&sighand->siglock);
908        if (signal_group_exit(sig))
909            /* Another thread got here before we took the lock. */
910            exit_code = sig->group_exit_code;
911        else {
912            sig->group_exit_code = exit_code;
913            sig->flags = SIGNAL_GROUP_EXIT;
914            zap_other_threads(current);
915        }
916        spin_unlock_irq(&sighand->siglock);
917    }
918
919    do_exit(exit_code);
920    /* NOTREACHED */
921}
922
923/*
924 * this kills every thread in the thread group. Note that any externally
925 * wait4()-ing process will get the correct exit code - even if this
926 * thread is not the thread group leader.
927 */
928SYSCALL_DEFINE1(exit_group, int, error_code)
929{
930    do_group_exit((error_code & 0xff) << 8);
931    /* NOTREACHED */
932    return 0;
933}
934
935struct wait_opts {
936    enum pid_type wo_type;
937    int wo_flags;
938    struct pid *wo_pid;
939
940    struct siginfo __user *wo_info;
941    int __user *wo_stat;
942    struct rusage __user *wo_rusage;
943
944    wait_queue_t child_wait;
945    int notask_error;
946};
947
948static inline
949struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
950{
951    if (type != PIDTYPE_PID)
952        task = task->group_leader;
953    return task->pids[type].pid;
954}
955
956static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
957{
958    return wo->wo_type == PIDTYPE_MAX ||
959        task_pid_type(p, wo->wo_type) == wo->wo_pid;
960}
961
962static int eligible_child(struct wait_opts *wo, struct task_struct *p)
963{
964    if (!eligible_pid(wo, p))
965        return 0;
966    /* Wait for all children (clone and not) if __WALL is set;
967     * otherwise, wait for clone children *only* if __WCLONE is
968     * set; otherwise, wait for non-clone children *only*. (Note:
969     * A "clone" child here is one that reports to its parent
970     * using a signal other than SIGCHLD.) */
971    if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
972        && !(wo->wo_flags & __WALL))
973        return 0;
974
975    return 1;
976}
977
978static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
979                pid_t pid, uid_t uid, int why, int status)
980{
981    struct siginfo __user *infop;
982    int retval = wo->wo_rusage
983        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
984
985    put_task_struct(p);
986    infop = wo->wo_info;
987    if (infop) {
988        if (!retval)
989            retval = put_user(SIGCHLD, &infop->si_signo);
990        if (!retval)
991            retval = put_user(0, &infop->si_errno);
992        if (!retval)
993            retval = put_user((short)why, &infop->si_code);
994        if (!retval)
995            retval = put_user(pid, &infop->si_pid);
996        if (!retval)
997            retval = put_user(uid, &infop->si_uid);
998        if (!retval)
999            retval = put_user(status, &infop->si_status);
1000    }
1001    if (!retval)
1002        retval = pid;
1003    return retval;
1004}
1005
1006/*
1007 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
1008 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1009 * the lock and this task is uninteresting. If we return nonzero, we have
1010 * released the lock and the system call should return.
1011 */
1012static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1013{
1014    unsigned long state;
1015    int retval, status, traced;
1016    pid_t pid = task_pid_vnr(p);
1017    uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1018    struct siginfo __user *infop;
1019
1020    if (!likely(wo->wo_flags & WEXITED))
1021        return 0;
1022
1023    if (unlikely(wo->wo_flags & WNOWAIT)) {
1024        int exit_code = p->exit_code;
1025        int why;
1026
1027        get_task_struct(p);
1028        read_unlock(&tasklist_lock);
1029        if ((exit_code & 0x7f) == 0) {
1030            why = CLD_EXITED;
1031            status = exit_code >> 8;
1032        } else {
1033            why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1034            status = exit_code & 0x7f;
1035        }
1036        return wait_noreap_copyout(wo, p, pid, uid, why, status);
1037    }
1038
1039    traced = ptrace_reparented(p);
1040    /*
1041     * Move the task's state to DEAD/TRACE, only one thread can do this.
1042     */
1043    state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
1044    if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1045        return 0;
1046    /*
1047     * It can be ptraced but not reparented, check
1048     * thread_group_leader() to filter out sub-threads.
1049     */
1050    if (likely(!traced) && thread_group_leader(p)) {
1051        struct signal_struct *psig;
1052        struct signal_struct *sig;
1053        unsigned long maxrss;
1054        cputime_t tgutime, tgstime;
1055
1056        /*
1057         * The resource counters for the group leader are in its
1058         * own task_struct. Those for dead threads in the group
1059         * are in its signal_struct, as are those for the child
1060         * processes it has previously reaped. All these
1061         * accumulate in the parent's signal_struct c* fields.
1062         *
1063         * We don't bother to take a lock here to protect these
1064         * p->signal fields, because they are only touched by
1065         * __exit_signal, which runs with tasklist_lock
1066         * write-locked anyway, and so is excluded here. We do
1067         * need to protect the access to parent->signal fields,
1068         * as other threads in the parent group can be right
1069         * here reaping other children at the same time.
1070         *
1071         * We use thread_group_cputime_adjusted() to get times for the thread
1072         * group, which consolidates times for all threads in the
1073         * group including the group leader.
1074         */
1075        thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1076        spin_lock_irq(&p->real_parent->sighand->siglock);
1077        psig = p->real_parent->signal;
1078        sig = p->signal;
1079        psig->cutime += tgutime + sig->cutime;
1080        psig->cstime += tgstime + sig->cstime;
1081        psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1082        psig->cmin_flt +=
1083            p->min_flt + sig->min_flt + sig->cmin_flt;
1084        psig->cmaj_flt +=
1085            p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1086        psig->cnvcsw +=
1087            p->nvcsw + sig->nvcsw + sig->cnvcsw;
1088        psig->cnivcsw +=
1089            p->nivcsw + sig->nivcsw + sig->cnivcsw;
1090        psig->cinblock +=
1091            task_io_get_inblock(p) +
1092            sig->inblock + sig->cinblock;
1093        psig->coublock +=
1094            task_io_get_oublock(p) +
1095            sig->oublock + sig->coublock;
1096        maxrss = max(sig->maxrss, sig->cmaxrss);
1097        if (psig->cmaxrss < maxrss)
1098            psig->cmaxrss = maxrss;
1099        task_io_accounting_add(&psig->ioac, &p->ioac);
1100        task_io_accounting_add(&psig->ioac, &sig->ioac);
1101        spin_unlock_irq(&p->real_parent->sighand->siglock);
1102    }
1103
1104    /*
1105     * Now we are sure this task is interesting, and no other
1106     * thread can reap it because we its state == DEAD/TRACE.
1107     */
1108    read_unlock(&tasklist_lock);
1109
1110    retval = wo->wo_rusage
1111        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1112    status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1113        ? p->signal->group_exit_code : p->exit_code;
1114    if (!retval && wo->wo_stat)
1115        retval = put_user(status, wo->wo_stat);
1116
1117    infop = wo->wo_info;
1118    if (!retval && infop)
1119        retval = put_user(SIGCHLD, &infop->si_signo);
1120    if (!retval && infop)
1121        retval = put_user(0, &infop->si_errno);
1122    if (!retval && infop) {
1123        int why;
1124
1125        if ((status & 0x7f) == 0) {
1126            why = CLD_EXITED;
1127            status >>= 8;
1128        } else {
1129            why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1130            status &= 0x7f;
1131        }
1132        retval = put_user((short)why, &infop->si_code);
1133        if (!retval)
1134            retval = put_user(status, &infop->si_status);
1135    }
1136    if (!retval && infop)
1137        retval = put_user(pid, &infop->si_pid);
1138    if (!retval && infop)
1139        retval = put_user(uid, &infop->si_uid);
1140    if (!retval)
1141        retval = pid;
1142
1143    if (state == EXIT_TRACE) {
1144        write_lock_irq(&tasklist_lock);
1145        /* We dropped tasklist, ptracer could die and untrace */
1146        ptrace_unlink(p);
1147
1148        /* If parent wants a zombie, don't release it now */
1149        state = EXIT_ZOMBIE;
1150        if (do_notify_parent(p, p->exit_signal))
1151            state = EXIT_DEAD;
1152        p->exit_state = state;
1153        write_unlock_irq(&tasklist_lock);
1154    }
1155    if (state == EXIT_DEAD)
1156        release_task(p);
1157
1158    return retval;
1159}
1160
1161static int *task_stopped_code(struct task_struct *p, bool ptrace)
1162{
1163    if (ptrace) {
1164        if (task_is_stopped_or_traced(p) &&
1165            !(p->jobctl & JOBCTL_LISTENING))
1166            return &p->exit_code;
1167    } else {
1168        if (p->signal->flags & SIGNAL_STOP_STOPPED)
1169            return &p->signal->group_exit_code;
1170    }
1171    return NULL;
1172}
1173
1174/**
1175 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1176 * @wo: wait options
1177 * @ptrace: is the wait for ptrace
1178 * @p: task to wait for
1179 *
1180 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1181 *
1182 * CONTEXT:
1183 * read_lock(&tasklist_lock), which is released if return value is
1184 * non-zero. Also, grabs and releases @p->sighand->siglock.
1185 *
1186 * RETURNS:
1187 * 0 if wait condition didn't exist and search for other wait conditions
1188 * should continue. Non-zero return, -errno on failure and @p's pid on
1189 * success, implies that tasklist_lock is released and wait condition
1190 * search should terminate.
1191 */
1192static int wait_task_stopped(struct wait_opts *wo,
1193                int ptrace, struct task_struct *p)
1194{
1195    struct siginfo __user *infop;
1196    int retval, exit_code, *p_code, why;
1197    uid_t uid = 0; /* unneeded, required by compiler */
1198    pid_t pid;
1199
1200    /*
1201     * Traditionally we see ptrace'd stopped tasks regardless of options.
1202     */
1203    if (!ptrace && !(wo->wo_flags & WUNTRACED))
1204        return 0;
1205
1206    if (!task_stopped_code(p, ptrace))
1207        return 0;
1208
1209    exit_code = 0;
1210    spin_lock_irq(&p->sighand->siglock);
1211
1212    p_code = task_stopped_code(p, ptrace);
1213    if (unlikely(!p_code))
1214        goto unlock_sig;
1215
1216    exit_code = *p_code;
1217    if (!exit_code)
1218        goto unlock_sig;
1219
1220    if (!unlikely(wo->wo_flags & WNOWAIT))
1221        *p_code = 0;
1222
1223    uid = from_kuid_munged(current_user_ns(), task_uid(p));
1224unlock_sig:
1225    spin_unlock_irq(&p->sighand->siglock);
1226    if (!exit_code)
1227        return 0;
1228
1229    /*
1230     * Now we are pretty sure this task is interesting.
1231     * Make sure it doesn't get reaped out from under us while we
1232     * give up the lock and then examine it below. We don't want to
1233     * keep holding onto the tasklist_lock while we call getrusage and
1234     * possibly take page faults for user memory.
1235     */
1236    get_task_struct(p);
1237    pid = task_pid_vnr(p);
1238    why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1239    read_unlock(&tasklist_lock);
1240
1241    if (unlikely(wo->wo_flags & WNOWAIT))
1242        return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1243
1244    retval = wo->wo_rusage
1245        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1246    if (!retval && wo->wo_stat)
1247        retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1248
1249    infop = wo->wo_info;
1250    if (!retval && infop)
1251        retval = put_user(SIGCHLD, &infop->si_signo);
1252    if (!retval && infop)
1253        retval = put_user(0, &infop->si_errno);
1254    if (!retval && infop)
1255        retval = put_user((short)why, &infop->si_code);
1256    if (!retval && infop)
1257        retval = put_user(exit_code, &infop->si_status);
1258    if (!retval && infop)
1259        retval = put_user(pid, &infop->si_pid);
1260    if (!retval && infop)
1261        retval = put_user(uid, &infop->si_uid);
1262    if (!retval)
1263        retval = pid;
1264    put_task_struct(p);
1265
1266    BUG_ON(!retval);
1267    return retval;
1268}
1269
1270/*
1271 * Handle do_wait work for one task in a live, non-stopped state.
1272 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1273 * the lock and this task is uninteresting. If we return nonzero, we have
1274 * released the lock and the system call should return.
1275 */
1276static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1277{
1278    int retval;
1279    pid_t pid;
1280    uid_t uid;
1281
1282    if (!unlikely(wo->wo_flags & WCONTINUED))
1283        return 0;
1284
1285    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1286        return 0;
1287
1288    spin_lock_irq(&p->sighand->siglock);
1289    /* Re-check with the lock held. */
1290    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1291        spin_unlock_irq(&p->sighand->siglock);
1292        return 0;
1293    }
1294    if (!unlikely(wo->wo_flags & WNOWAIT))
1295        p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1296    uid = from_kuid_munged(current_user_ns(), task_uid(p));
1297    spin_unlock_irq(&p->sighand->siglock);
1298
1299    pid = task_pid_vnr(p);
1300    get_task_struct(p);
1301    read_unlock(&tasklist_lock);
1302
1303    if (!wo->wo_info) {
1304        retval = wo->wo_rusage
1305            ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1306        put_task_struct(p);
1307        if (!retval && wo->wo_stat)
1308            retval = put_user(0xffff, wo->wo_stat);
1309        if (!retval)
1310            retval = pid;
1311    } else {
1312        retval = wait_noreap_copyout(wo, p, pid, uid,
1313                         CLD_CONTINUED, SIGCONT);
1314        BUG_ON(retval == 0);
1315    }
1316
1317    return retval;
1318}
1319
1320/*
1321 * Consider @p for a wait by @parent.
1322 *
1323 * -ECHILD should be in ->notask_error before the first call.
1324 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1325 * Returns zero if the search for a child should continue;
1326 * then ->notask_error is 0 if @p is an eligible child,
1327 * or another error from security_task_wait(), or still -ECHILD.
1328 */
1329static int wait_consider_task(struct wait_opts *wo, int ptrace,
1330                struct task_struct *p)
1331{
1332    int ret;
1333
1334    if (unlikely(p->exit_state == EXIT_DEAD))
1335        return 0;
1336
1337    ret = eligible_child(wo, p);
1338    if (!ret)
1339        return ret;
1340
1341    ret = security_task_wait(p);
1342    if (unlikely(ret < 0)) {
1343        /*
1344         * If we have not yet seen any eligible child,
1345         * then let this error code replace -ECHILD.
1346         * A permission error will give the user a clue
1347         * to look for security policy problems, rather
1348         * than for mysterious wait bugs.
1349         */
1350        if (wo->notask_error)
1351            wo->notask_error = ret;
1352        return 0;
1353    }
1354
1355    if (unlikely(p->exit_state == EXIT_TRACE)) {
1356        /*
1357         * ptrace == 0 means we are the natural parent. In this case
1358         * we should clear notask_error, debugger will notify us.
1359         */
1360        if (likely(!ptrace))
1361            wo->notask_error = 0;
1362        return 0;
1363    }
1364
1365    if (likely(!ptrace) && unlikely(p->ptrace)) {
1366        /*
1367         * If it is traced by its real parent's group, just pretend
1368         * the caller is ptrace_do_wait() and reap this child if it
1369         * is zombie.
1370         *
1371         * This also hides group stop state from real parent; otherwise
1372         * a single stop can be reported twice as group and ptrace stop.
1373         * If a ptracer wants to distinguish these two events for its
1374         * own children it should create a separate process which takes
1375         * the role of real parent.
1376         */
1377        if (!ptrace_reparented(p))
1378            ptrace = 1;
1379    }
1380
1381    /* slay zombie? */
1382    if (p->exit_state == EXIT_ZOMBIE) {
1383        /* we don't reap group leaders with subthreads */
1384        if (!delay_group_leader(p)) {
1385            /*
1386             * A zombie ptracee is only visible to its ptracer.
1387             * Notification and reaping will be cascaded to the
1388             * real parent when the ptracer detaches.
1389             */
1390            if (unlikely(ptrace) || likely(!p->ptrace))
1391                return wait_task_zombie(wo, p);
1392        }
1393
1394        /*
1395         * Allow access to stopped/continued state via zombie by
1396         * falling through. Clearing of notask_error is complex.
1397         *
1398         * When !@ptrace:
1399         *
1400         * If WEXITED is set, notask_error should naturally be
1401         * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1402         * so, if there are live subthreads, there are events to
1403         * wait for. If all subthreads are dead, it's still safe
1404         * to clear - this function will be called again in finite
1405         * amount time once all the subthreads are released and
1406         * will then return without clearing.
1407         *
1408         * When @ptrace:
1409         *
1410         * Stopped state is per-task and thus can't change once the
1411         * target task dies. Only continued and exited can happen.
1412         * Clear notask_error if WCONTINUED | WEXITED.
1413         */
1414        if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1415            wo->notask_error = 0;
1416    } else {
1417        /*
1418         * @p is alive and it's gonna stop, continue or exit, so
1419         * there always is something to wait for.
1420         */
1421        wo->notask_error = 0;
1422    }
1423
1424    /*
1425     * Wait for stopped. Depending on @ptrace, different stopped state
1426     * is used and the two don't interact with each other.
1427     */
1428    ret = wait_task_stopped(wo, ptrace, p);
1429    if (ret)
1430        return ret;
1431
1432    /*
1433     * Wait for continued. There's only one continued state and the
1434     * ptracer can consume it which can confuse the real parent. Don't
1435     * use WCONTINUED from ptracer. You don't need or want it.
1436     */
1437    return wait_task_continued(wo, p);
1438}
1439
1440/*
1441 * Do the work of do_wait() for one thread in the group, @tsk.
1442 *
1443 * -ECHILD should be in ->notask_error before the first call.
1444 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1445 * Returns zero if the search for a child should continue; then
1446 * ->notask_error is 0 if there were any eligible children,
1447 * or another error from security_task_wait(), or still -ECHILD.
1448 */
1449static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1450{
1451    struct task_struct *p;
1452
1453    list_for_each_entry(p, &tsk->children, sibling) {
1454        int ret = wait_consider_task(wo, 0, p);
1455        if (ret)
1456            return ret;
1457    }
1458
1459    return 0;
1460}
1461
1462static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1463{
1464    struct task_struct *p;
1465
1466    list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1467        int ret = wait_consider_task(wo, 1, p);
1468        if (ret)
1469            return ret;
1470    }
1471
1472    return 0;
1473}
1474
1475static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1476                int sync, void *key)
1477{
1478    struct wait_opts *wo = container_of(wait, struct wait_opts,
1479                        child_wait);
1480    struct task_struct *p = key;
1481
1482    if (!eligible_pid(wo, p))
1483        return 0;
1484
1485    if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1486        return 0;
1487
1488    return default_wake_function(wait, mode, sync, key);
1489}
1490
1491void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1492{
1493    __wake_up_sync_key(&parent->signal->wait_chldexit,
1494                TASK_INTERRUPTIBLE, 1, p);
1495}
1496
1497static long do_wait(struct wait_opts *wo)
1498{
1499    struct task_struct *tsk;
1500    int retval;
1501
1502    trace_sched_process_wait(wo->wo_pid);
1503
1504    init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1505    wo->child_wait.private = current;
1506    add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1507repeat:
1508    /*
1509     * If there is nothing that can match our critiera just get out.
1510     * We will clear ->notask_error to zero if we see any child that
1511     * might later match our criteria, even if we are not able to reap
1512     * it yet.
1513     */
1514    wo->notask_error = -ECHILD;
1515    if ((wo->wo_type < PIDTYPE_MAX) &&
1516       (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1517        goto notask;
1518
1519    set_current_state(TASK_INTERRUPTIBLE);
1520    read_lock(&tasklist_lock);
1521    tsk = current;
1522    do {
1523        retval = do_wait_thread(wo, tsk);
1524        if (retval)
1525            goto end;
1526
1527        retval = ptrace_do_wait(wo, tsk);
1528        if (retval)
1529            goto end;
1530
1531        if (wo->wo_flags & __WNOTHREAD)
1532            break;
1533    } while_each_thread(current, tsk);
1534    read_unlock(&tasklist_lock);
1535
1536notask:
1537    retval = wo->notask_error;
1538    if (!retval && !(wo->wo_flags & WNOHANG)) {
1539        retval = -ERESTARTSYS;
1540        if (!signal_pending(current)) {
1541            schedule();
1542            goto repeat;
1543        }
1544    }
1545end:
1546    __set_current_state(TASK_RUNNING);
1547    remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1548    return retval;
1549}
1550
1551SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1552        infop, int, options, struct rusage __user *, ru)
1553{
1554    struct wait_opts wo;
1555    struct pid *pid = NULL;
1556    enum pid_type type;
1557    long ret;
1558
1559    if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1560        return -EINVAL;
1561    if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1562        return -EINVAL;
1563
1564    switch (which) {
1565    case P_ALL:
1566        type = PIDTYPE_MAX;
1567        break;
1568    case P_PID:
1569        type = PIDTYPE_PID;
1570        if (upid <= 0)
1571            return -EINVAL;
1572        break;
1573    case P_PGID:
1574        type = PIDTYPE_PGID;
1575        if (upid <= 0)
1576            return -EINVAL;
1577        break;
1578    default:
1579        return -EINVAL;
1580    }
1581
1582    if (type < PIDTYPE_MAX)
1583        pid = find_get_pid(upid);
1584
1585    wo.wo_type = type;
1586    wo.wo_pid = pid;
1587    wo.wo_flags = options;
1588    wo.wo_info = infop;
1589    wo.wo_stat = NULL;
1590    wo.wo_rusage = ru;
1591    ret = do_wait(&wo);
1592
1593    if (ret > 0) {
1594        ret = 0;
1595    } else if (infop) {
1596        /*
1597         * For a WNOHANG return, clear out all the fields
1598         * we would set so the user can easily tell the
1599         * difference.
1600         */
1601        if (!ret)
1602            ret = put_user(0, &infop->si_signo);
1603        if (!ret)
1604            ret = put_user(0, &infop->si_errno);
1605        if (!ret)
1606            ret = put_user(0, &infop->si_code);
1607        if (!ret)
1608            ret = put_user(0, &infop->si_pid);
1609        if (!ret)
1610            ret = put_user(0, &infop->si_uid);
1611        if (!ret)
1612            ret = put_user(0, &infop->si_status);
1613    }
1614
1615    put_pid(pid);
1616    return ret;
1617}
1618
1619SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1620        int, options, struct rusage __user *, ru)
1621{
1622    struct wait_opts wo;
1623    struct pid *pid = NULL;
1624    enum pid_type type;
1625    long ret;
1626
1627    if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1628            __WNOTHREAD|__WCLONE|__WALL))
1629        return -EINVAL;
1630
1631    if (upid == -1)
1632        type = PIDTYPE_MAX;
1633    else if (upid < 0) {
1634        type = PIDTYPE_PGID;
1635        pid = find_get_pid(-upid);
1636    } else if (upid == 0) {
1637        type = PIDTYPE_PGID;
1638        pid = get_task_pid(current, PIDTYPE_PGID);
1639    } else /* upid > 0 */ {
1640        type = PIDTYPE_PID;
1641        pid = find_get_pid(upid);
1642    }
1643
1644    wo.wo_type = type;
1645    wo.wo_pid = pid;
1646    wo.wo_flags = options | WEXITED;
1647    wo.wo_info = NULL;
1648    wo.wo_stat = stat_addr;
1649    wo.wo_rusage = ru;
1650    ret = do_wait(&wo);
1651    put_pid(pid);
1652
1653    return ret;
1654}
1655
1656#ifdef __ARCH_WANT_SYS_WAITPID
1657
1658/*
1659 * sys_waitpid() remains for compatibility. waitpid() should be
1660 * implemented by calling sys_wait4() from libc.a.
1661 */
1662SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1663{
1664    return sys_wait4(pid, stat_addr, options, NULL);
1665}
1666
1667#endif
1668

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