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/binfmts.h>
24#include <linux/nsproxy.h>
25#include <linux/pid_namespace.h>
26#include <linux/ptrace.h>
27#include <linux/profile.h>
28#include <linux/mount.h>
29#include <linux/proc_fs.h>
30#include <linux/kthread.h>
31#include <linux/mempolicy.h>
32#include <linux/taskstats_kern.h>
33#include <linux/delayacct.h>
34#include <linux/freezer.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         * If we are the last child process in a pid namespace to be
77         * reaped, notify the reaper sleeping zap_pid_ns_processes().
78         */
79        if (IS_ENABLED(CONFIG_PID_NS)) {
80            struct task_struct *parent = p->real_parent;
81
82            if ((task_active_pid_ns(parent)->child_reaper == parent) &&
83                list_empty(&parent->children) &&
84                (parent->flags & PF_EXITING))
85                wake_up_process(parent);
86        }
87    }
88    list_del_rcu(&p->thread_group);
89}
90
91/*
92 * This function expects the tasklist_lock write-locked.
93 */
94static void __exit_signal(struct task_struct *tsk)
95{
96    struct signal_struct *sig = tsk->signal;
97    bool group_dead = thread_group_leader(tsk);
98    struct sighand_struct *sighand;
99    struct tty_struct *uninitialized_var(tty);
100
101    sighand = rcu_dereference_check(tsk->sighand,
102                    lockdep_tasklist_lock_is_held());
103    spin_lock(&sighand->siglock);
104
105    posix_cpu_timers_exit(tsk);
106    if (group_dead) {
107        posix_cpu_timers_exit_group(tsk);
108        tty = sig->tty;
109        sig->tty = NULL;
110    } else {
111        /*
112         * This can only happen if the caller is de_thread().
113         * FIXME: this is the temporary hack, we should teach
114         * posix-cpu-timers to handle this case correctly.
115         */
116        if (unlikely(has_group_leader_pid(tsk)))
117            posix_cpu_timers_exit_group(tsk);
118
119        /*
120         * If there is any task waiting for the group exit
121         * then notify it:
122         */
123        if (sig->notify_count > 0 && !--sig->notify_count)
124            wake_up_process(sig->group_exit_task);
125
126        if (tsk == sig->curr_target)
127            sig->curr_target = next_thread(tsk);
128        /*
129         * Accumulate here the counters for all threads but the
130         * group leader as they die, so they can be added into
131         * the process-wide totals when those are taken.
132         * The group leader stays around as a zombie as long
133         * as there are other threads. When it gets reaped,
134         * the exit.c code will add its counts into these totals.
135         * We won't ever get here for the group leader, since it
136         * will have been the last reference on the signal_struct.
137         */
138        sig->utime += tsk->utime;
139        sig->stime += tsk->stime;
140        sig->gtime += tsk->gtime;
141        sig->min_flt += tsk->min_flt;
142        sig->maj_flt += tsk->maj_flt;
143        sig->nvcsw += tsk->nvcsw;
144        sig->nivcsw += tsk->nivcsw;
145        sig->inblock += task_io_get_inblock(tsk);
146        sig->oublock += task_io_get_oublock(tsk);
147        task_io_accounting_add(&sig->ioac, &tsk->ioac);
148        sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
149    }
150
151    sig->nr_threads--;
152    __unhash_process(tsk, group_dead);
153
154    /*
155     * Do this under ->siglock, we can race with another thread
156     * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
157     */
158    flush_sigqueue(&tsk->pending);
159    tsk->sighand = NULL;
160    spin_unlock(&sighand->siglock);
161
162    __cleanup_sighand(sighand);
163    clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
164    if (group_dead) {
165        flush_sigqueue(&sig->shared_pending);
166        tty_kref_put(tty);
167    }
168}
169
170static void delayed_put_task_struct(struct rcu_head *rhp)
171{
172    struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
173
174    perf_event_delayed_put(tsk);
175    trace_sched_process_free(tsk);
176    put_task_struct(tsk);
177}
178
179
180void release_task(struct task_struct * p)
181{
182    struct task_struct *leader;
183    int zap_leader;
184repeat:
185    /* don't need to get the RCU readlock here - the process is dead and
186     * can't be modifying its own credentials. But shut RCU-lockdep up */
187    rcu_read_lock();
188    atomic_dec(&__task_cred(p)->user->processes);
189    rcu_read_unlock();
190
191    proc_flush_task(p);
192
193    write_lock_irq(&tasklist_lock);
194    ptrace_release_task(p);
195    __exit_signal(p);
196
197    /*
198     * If we are the last non-leader member of the thread
199     * group, and the leader is zombie, then notify the
200     * group leader's parent process. (if it wants notification.)
201     */
202    zap_leader = 0;
203    leader = p->group_leader;
204    if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
205        /*
206         * If we were the last child thread and the leader has
207         * exited already, and the leader's parent ignores SIGCHLD,
208         * then we are the one who should release the leader.
209         */
210        zap_leader = do_notify_parent(leader, leader->exit_signal);
211        if (zap_leader)
212            leader->exit_state = EXIT_DEAD;
213    }
214
215    write_unlock_irq(&tasklist_lock);
216    release_thread(p);
217    call_rcu(&p->rcu, delayed_put_task_struct);
218
219    p = leader;
220    if (unlikely(zap_leader))
221        goto repeat;
222}
223
224/*
225 * This checks not only the pgrp, but falls back on the pid if no
226 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
227 * without this...
228 *
229 * The caller must hold rcu lock or the tasklist lock.
230 */
231struct pid *session_of_pgrp(struct pid *pgrp)
232{
233    struct task_struct *p;
234    struct pid *sid = NULL;
235
236    p = pid_task(pgrp, PIDTYPE_PGID);
237    if (p == NULL)
238        p = pid_task(pgrp, PIDTYPE_PID);
239    if (p != NULL)
240        sid = task_session(p);
241
242    return sid;
243}
244
245/*
246 * Determine if a process group is "orphaned", according to the POSIX
247 * definition in 2.2.2.52. Orphaned process groups are not to be affected
248 * by terminal-generated stop signals. Newly orphaned process groups are
249 * to receive a SIGHUP and a SIGCONT.
250 *
251 * "I ask you, have you ever known what it is to be an orphan?"
252 */
253static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
254{
255    struct task_struct *p;
256
257    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
258        if ((p == ignored_task) ||
259            (p->exit_state && thread_group_empty(p)) ||
260            is_global_init(p->real_parent))
261            continue;
262
263        if (task_pgrp(p->real_parent) != pgrp &&
264            task_session(p->real_parent) == task_session(p))
265            return 0;
266    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
267
268    return 1;
269}
270
271int is_current_pgrp_orphaned(void)
272{
273    int retval;
274
275    read_lock(&tasklist_lock);
276    retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
277    read_unlock(&tasklist_lock);
278
279    return retval;
280}
281
282static bool has_stopped_jobs(struct pid *pgrp)
283{
284    struct task_struct *p;
285
286    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
287        if (p->signal->flags & SIGNAL_STOP_STOPPED)
288            return true;
289    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
290
291    return false;
292}
293
294/*
295 * Check to see if any process groups have become orphaned as
296 * a result of our exiting, and if they have any stopped jobs,
297 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
298 */
299static void
300kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
301{
302    struct pid *pgrp = task_pgrp(tsk);
303    struct task_struct *ignored_task = tsk;
304
305    if (!parent)
306         /* exit: our father is in a different pgrp than
307          * we are and we were the only connection outside.
308          */
309        parent = tsk->real_parent;
310    else
311        /* reparent: our child is in a different pgrp than
312         * we are, and it was the only connection outside.
313         */
314        ignored_task = NULL;
315
316    if (task_pgrp(parent) != pgrp &&
317        task_session(parent) == task_session(tsk) &&
318        will_become_orphaned_pgrp(pgrp, ignored_task) &&
319        has_stopped_jobs(pgrp)) {
320        __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
321        __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
322    }
323}
324
325/**
326 * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
327 *
328 * If a kernel thread is launched as a result of a system call, or if
329 * it ever exits, it should generally reparent itself to kthreadd so it
330 * isn't in the way of other processes and is correctly cleaned up on exit.
331 *
332 * The various task state such as scheduling policy and priority may have
333 * been inherited from a user process, so we reset them to sane values here.
334 *
335 * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
336 */
337static void reparent_to_kthreadd(void)
338{
339    write_lock_irq(&tasklist_lock);
340
341    ptrace_unlink(current);
342    /* Reparent to init */
343    current->real_parent = current->parent = kthreadd_task;
344    list_move_tail(&current->sibling, &current->real_parent->children);
345
346    /* Set the exit signal to SIGCHLD so we signal init on exit */
347    current->exit_signal = SIGCHLD;
348
349    if (task_nice(current) < 0)
350        set_user_nice(current, 0);
351    /* cpus_allowed? */
352    /* rt_priority? */
353    /* signals? */
354    memcpy(current->signal->rlim, init_task.signal->rlim,
355           sizeof(current->signal->rlim));
356
357    atomic_inc(&init_cred.usage);
358    commit_creds(&init_cred);
359    write_unlock_irq(&tasklist_lock);
360}
361
362void __set_special_pids(struct pid *pid)
363{
364    struct task_struct *curr = current->group_leader;
365
366    if (task_session(curr) != pid)
367        change_pid(curr, PIDTYPE_SID, pid);
368
369    if (task_pgrp(curr) != pid)
370        change_pid(curr, PIDTYPE_PGID, pid);
371}
372
373static void set_special_pids(struct pid *pid)
374{
375    write_lock_irq(&tasklist_lock);
376    __set_special_pids(pid);
377    write_unlock_irq(&tasklist_lock);
378}
379
380/*
381 * Let kernel threads use this to say that they allow a certain signal.
382 * Must not be used if kthread was cloned with CLONE_SIGHAND.
383 */
384int allow_signal(int sig)
385{
386    if (!valid_signal(sig) || sig < 1)
387        return -EINVAL;
388
389    spin_lock_irq(&current->sighand->siglock);
390    /* This is only needed for daemonize()'ed kthreads */
391    sigdelset(&current->blocked, sig);
392    /*
393     * Kernel threads handle their own signals. Let the signal code
394     * know it'll be handled, so that they don't get converted to
395     * SIGKILL or just silently dropped.
396     */
397    current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
398    recalc_sigpending();
399    spin_unlock_irq(&current->sighand->siglock);
400    return 0;
401}
402
403EXPORT_SYMBOL(allow_signal);
404
405int disallow_signal(int sig)
406{
407    if (!valid_signal(sig) || sig < 1)
408        return -EINVAL;
409
410    spin_lock_irq(&current->sighand->siglock);
411    current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
412    recalc_sigpending();
413    spin_unlock_irq(&current->sighand->siglock);
414    return 0;
415}
416
417EXPORT_SYMBOL(disallow_signal);
418
419/*
420 * Put all the gunge required to become a kernel thread without
421 * attached user resources in one place where it belongs.
422 */
423
424void daemonize(const char *name, ...)
425{
426    va_list args;
427    sigset_t blocked;
428
429    va_start(args, name);
430    vsnprintf(current->comm, sizeof(current->comm), name, args);
431    va_end(args);
432
433    /*
434     * If we were started as result of loading a module, close all of the
435     * user space pages. We don't need them, and if we didn't close them
436     * they would be locked into memory.
437     */
438    exit_mm(current);
439    /*
440     * We don't want to get frozen, in case system-wide hibernation
441     * or suspend transition begins right now.
442     */
443    current->flags |= (PF_NOFREEZE | PF_KTHREAD);
444
445    if (current->nsproxy != &init_nsproxy) {
446        get_nsproxy(&init_nsproxy);
447        switch_task_namespaces(current, &init_nsproxy);
448    }
449    set_special_pids(&init_struct_pid);
450    proc_clear_tty(current);
451
452    /* Block and flush all signals */
453    sigfillset(&blocked);
454    sigprocmask(SIG_BLOCK, &blocked, NULL);
455    flush_signals(current);
456
457    /* Become as one with the init task */
458
459    daemonize_fs_struct();
460    exit_files(current);
461    current->files = init_task.files;
462    atomic_inc(&current->files->count);
463
464    reparent_to_kthreadd();
465}
466
467EXPORT_SYMBOL(daemonize);
468
469static void close_files(struct files_struct * files)
470{
471    int i, j;
472    struct fdtable *fdt;
473
474    j = 0;
475
476    /*
477     * It is safe to dereference the fd table without RCU or
478     * ->file_lock because this is the last reference to the
479     * files structure. But use RCU to shut RCU-lockdep up.
480     */
481    rcu_read_lock();
482    fdt = files_fdtable(files);
483    rcu_read_unlock();
484    for (;;) {
485        unsigned long set;
486        i = j * __NFDBITS;
487        if (i >= fdt->max_fds)
488            break;
489        set = fdt->open_fds[j++];
490        while (set) {
491            if (set & 1) {
492                struct file * file = xchg(&fdt->fd[i], NULL);
493                if (file) {
494                    filp_close(file, files);
495                    cond_resched();
496                }
497            }
498            i++;
499            set >>= 1;
500        }
501    }
502}
503
504struct files_struct *get_files_struct(struct task_struct *task)
505{
506    struct files_struct *files;
507
508    task_lock(task);
509    files = task->files;
510    if (files)
511        atomic_inc(&files->count);
512    task_unlock(task);
513
514    return files;
515}
516
517void put_files_struct(struct files_struct *files)
518{
519    struct fdtable *fdt;
520
521    if (atomic_dec_and_test(&files->count)) {
522        close_files(files);
523        /*
524         * Free the fd and fdset arrays if we expanded them.
525         * If the fdtable was embedded, pass files for freeing
526         * at the end of the RCU grace period. Otherwise,
527         * you can free files immediately.
528         */
529        rcu_read_lock();
530        fdt = files_fdtable(files);
531        if (fdt != &files->fdtab)
532            kmem_cache_free(files_cachep, files);
533        free_fdtable(fdt);
534        rcu_read_unlock();
535    }
536}
537
538void reset_files_struct(struct files_struct *files)
539{
540    struct task_struct *tsk = current;
541    struct files_struct *old;
542
543    old = tsk->files;
544    task_lock(tsk);
545    tsk->files = files;
546    task_unlock(tsk);
547    put_files_struct(old);
548}
549
550void exit_files(struct task_struct *tsk)
551{
552    struct files_struct * files = tsk->files;
553
554    if (files) {
555        task_lock(tsk);
556        tsk->files = NULL;
557        task_unlock(tsk);
558        put_files_struct(files);
559    }
560}
561
562#ifdef CONFIG_MM_OWNER
563/*
564 * A task is exiting. If it owned this mm, find a new owner for the mm.
565 */
566void mm_update_next_owner(struct mm_struct *mm)
567{
568    struct task_struct *c, *g, *p = current;
569
570retry:
571    /*
572     * If the exiting or execing task is not the owner, it's
573     * someone else's problem.
574     */
575    if (mm->owner != p)
576        return;
577    /*
578     * The current owner is exiting/execing and there are no other
579     * candidates. Do not leave the mm pointing to a possibly
580     * freed task structure.
581     */
582    if (atomic_read(&mm->mm_users) <= 1) {
583        mm->owner = NULL;
584        return;
585    }
586
587    read_lock(&tasklist_lock);
588    /*
589     * Search in the children
590     */
591    list_for_each_entry(c, &p->children, sibling) {
592        if (c->mm == mm)
593            goto assign_new_owner;
594    }
595
596    /*
597     * Search in the siblings
598     */
599    list_for_each_entry(c, &p->real_parent->children, sibling) {
600        if (c->mm == mm)
601            goto assign_new_owner;
602    }
603
604    /*
605     * Search through everything else. We should not get
606     * here often
607     */
608    do_each_thread(g, c) {
609        if (c->mm == mm)
610            goto assign_new_owner;
611    } while_each_thread(g, c);
612
613    read_unlock(&tasklist_lock);
614    /*
615     * We found no owner yet mm_users > 1: this implies that we are
616     * most likely racing with swapoff (try_to_unuse()) or /proc or
617     * ptrace or page migration (get_task_mm()). Mark owner as NULL.
618     */
619    mm->owner = NULL;
620    return;
621
622assign_new_owner:
623    BUG_ON(c == p);
624    get_task_struct(c);
625    /*
626     * The task_lock protects c->mm from changing.
627     * We always want mm->owner->mm == mm
628     */
629    task_lock(c);
630    /*
631     * Delay read_unlock() till we have the task_lock()
632     * to ensure that c does not slip away underneath us
633     */
634    read_unlock(&tasklist_lock);
635    if (c->mm != mm) {
636        task_unlock(c);
637        put_task_struct(c);
638        goto retry;
639    }
640    mm->owner = c;
641    task_unlock(c);
642    put_task_struct(c);
643}
644#endif /* CONFIG_MM_OWNER */
645
646/*
647 * Turn us into a lazy TLB process if we
648 * aren't already..
649 */
650static void exit_mm(struct task_struct * tsk)
651{
652    struct mm_struct *mm = tsk->mm;
653    struct core_state *core_state;
654
655    mm_release(tsk, mm);
656    if (!mm)
657        return;
658    sync_mm_rss(mm);
659    /*
660     * Serialize with any possible pending coredump.
661     * We must hold mmap_sem around checking core_state
662     * and clearing tsk->mm. The core-inducing thread
663     * will increment ->nr_threads for each thread in the
664     * group with ->mm != NULL.
665     */
666    down_read(&mm->mmap_sem);
667    core_state = mm->core_state;
668    if (core_state) {
669        struct core_thread self;
670        up_read(&mm->mmap_sem);
671
672        self.task = tsk;
673        self.next = xchg(&core_state->dumper.next, &self);
674        /*
675         * Implies mb(), the result of xchg() must be visible
676         * to core_state->dumper.
677         */
678        if (atomic_dec_and_test(&core_state->nr_threads))
679            complete(&core_state->startup);
680
681        for (;;) {
682            set_task_state(tsk, TASK_UNINTERRUPTIBLE);
683            if (!self.task) /* see coredump_finish() */
684                break;
685            schedule();
686        }
687        __set_task_state(tsk, TASK_RUNNING);
688        down_read(&mm->mmap_sem);
689    }
690    atomic_inc(&mm->mm_count);
691    BUG_ON(mm != tsk->active_mm);
692    /* more a memory barrier than a real lock */
693    task_lock(tsk);
694    tsk->mm = NULL;
695    up_read(&mm->mmap_sem);
696    enter_lazy_tlb(mm, current);
697    task_unlock(tsk);
698    mm_update_next_owner(mm);
699    mmput(mm);
700}
701
702/*
703 * When we die, we re-parent all our children, and try to:
704 * 1. give them to another thread in our thread group, if such a member exists
705 * 2. give it to the first ancestor process which prctl'd itself as a
706 * child_subreaper for its children (like a service manager)
707 * 3. give it to the init process (PID 1) in our pid namespace
708 */
709static struct task_struct *find_new_reaper(struct task_struct *father)
710    __releases(&tasklist_lock)
711    __acquires(&tasklist_lock)
712{
713    struct pid_namespace *pid_ns = task_active_pid_ns(father);
714    struct task_struct *thread;
715
716    thread = father;
717    while_each_thread(father, thread) {
718        if (thread->flags & PF_EXITING)
719            continue;
720        if (unlikely(pid_ns->child_reaper == father))
721            pid_ns->child_reaper = thread;
722        return thread;
723    }
724
725    if (unlikely(pid_ns->child_reaper == father)) {
726        write_unlock_irq(&tasklist_lock);
727        if (unlikely(pid_ns == &init_pid_ns)) {
728            panic("Attempted to kill init! exitcode=0x%08x\n",
729                father->signal->group_exit_code ?:
730                    father->exit_code);
731        }
732
733        zap_pid_ns_processes(pid_ns);
734        write_lock_irq(&tasklist_lock);
735    } else if (father->signal->has_child_subreaper) {
736        struct task_struct *reaper;
737
738        /*
739         * Find the first ancestor marked as child_subreaper.
740         * Note that the code below checks same_thread_group(reaper,
741         * pid_ns->child_reaper). This is what we need to DTRT in a
742         * PID namespace. However we still need the check above, see
743         * http://marc.info/?l=linux-kernel&m=131385460420380
744         */
745        for (reaper = father->real_parent;
746             reaper != &init_task;
747             reaper = reaper->real_parent) {
748            if (same_thread_group(reaper, pid_ns->child_reaper))
749                break;
750            if (!reaper->signal->is_child_subreaper)
751                continue;
752            thread = reaper;
753            do {
754                if (!(thread->flags & PF_EXITING))
755                    return reaper;
756            } while_each_thread(reaper, thread);
757        }
758    }
759
760    return pid_ns->child_reaper;
761}
762
763/*
764* Any that need to be release_task'd are put on the @dead list.
765 */
766static void reparent_leader(struct task_struct *father, struct task_struct *p,
767                struct list_head *dead)
768{
769    list_move_tail(&p->sibling, &p->real_parent->children);
770
771    if (p->exit_state == EXIT_DEAD)
772        return;
773    /*
774     * If this is a threaded reparent there is no need to
775     * notify anyone anything has happened.
776     */
777    if (same_thread_group(p->real_parent, father))
778        return;
779
780    /* We don't want people slaying init. */
781    p->exit_signal = SIGCHLD;
782
783    /* If it has exited notify the new parent about this child's death. */
784    if (!p->ptrace &&
785        p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
786        if (do_notify_parent(p, p->exit_signal)) {
787            p->exit_state = EXIT_DEAD;
788            list_move_tail(&p->sibling, dead);
789        }
790    }
791
792    kill_orphaned_pgrp(p, father);
793}
794
795static void forget_original_parent(struct task_struct *father)
796{
797    struct task_struct *p, *n, *reaper;
798    LIST_HEAD(dead_children);
799
800    write_lock_irq(&tasklist_lock);
801    /*
802     * Note that exit_ptrace() and find_new_reaper() might
803     * drop tasklist_lock and reacquire it.
804     */
805    exit_ptrace(father);
806    reaper = find_new_reaper(father);
807
808    list_for_each_entry_safe(p, n, &father->children, sibling) {
809        struct task_struct *t = p;
810        do {
811            t->real_parent = reaper;
812            if (t->parent == father) {
813                BUG_ON(t->ptrace);
814                t->parent = t->real_parent;
815            }
816            if (t->pdeath_signal)
817                group_send_sig_info(t->pdeath_signal,
818                            SEND_SIG_NOINFO, t);
819        } while_each_thread(p, t);
820        reparent_leader(father, p, &dead_children);
821    }
822    write_unlock_irq(&tasklist_lock);
823
824    BUG_ON(!list_empty(&father->children));
825
826    list_for_each_entry_safe(p, n, &dead_children, sibling) {
827        list_del_init(&p->sibling);
828        release_task(p);
829    }
830}
831
832/*
833 * Send signals to all our closest relatives so that they know
834 * to properly mourn us..
835 */
836static void exit_notify(struct task_struct *tsk, int group_dead)
837{
838    bool autoreap;
839
840    /*
841     * This does two things:
842     *
843       * A. Make init inherit all the child processes
844     * B. Check to see if any process groups have become orphaned
845     * as a result of our exiting, and if they have any stopped
846     * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
847     */
848    forget_original_parent(tsk);
849    exit_task_namespaces(tsk);
850
851    write_lock_irq(&tasklist_lock);
852    if (group_dead)
853        kill_orphaned_pgrp(tsk->group_leader, NULL);
854
855    if (unlikely(tsk->ptrace)) {
856        int sig = thread_group_leader(tsk) &&
857                thread_group_empty(tsk) &&
858                !ptrace_reparented(tsk) ?
859            tsk->exit_signal : SIGCHLD;
860        autoreap = do_notify_parent(tsk, sig);
861    } else if (thread_group_leader(tsk)) {
862        autoreap = thread_group_empty(tsk) &&
863            do_notify_parent(tsk, tsk->exit_signal);
864    } else {
865        autoreap = true;
866    }
867
868    tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
869
870    /* mt-exec, de_thread() is waiting for group leader */
871    if (unlikely(tsk->signal->notify_count < 0))
872        wake_up_process(tsk->signal->group_exit_task);
873    write_unlock_irq(&tasklist_lock);
874
875    /* If the process is dead, release it - nobody will wait for it */
876    if (autoreap)
877        release_task(tsk);
878}
879
880#ifdef CONFIG_DEBUG_STACK_USAGE
881static void check_stack_usage(void)
882{
883    static DEFINE_SPINLOCK(low_water_lock);
884    static int lowest_to_date = THREAD_SIZE;
885    unsigned long free;
886
887    free = stack_not_used(current);
888
889    if (free >= lowest_to_date)
890        return;
891
892    spin_lock(&low_water_lock);
893    if (free < lowest_to_date) {
894        printk(KERN_WARNING "%s (%d) used greatest stack depth: "
895                "%lu bytes left\n",
896                current->comm, task_pid_nr(current), free);
897        lowest_to_date = free;
898    }
899    spin_unlock(&low_water_lock);
900}
901#else
902static inline void check_stack_usage(void) {}
903#endif
904
905void do_exit(long code)
906{
907    struct task_struct *tsk = current;
908    int group_dead;
909
910    profile_task_exit(tsk);
911
912    WARN_ON(blk_needs_flush_plug(tsk));
913
914    if (unlikely(in_interrupt()))
915        panic("Aiee, killing interrupt handler!");
916    if (unlikely(!tsk->pid))
917        panic("Attempted to kill the idle task!");
918
919    /*
920     * If do_exit is called because this processes oopsed, it's possible
921     * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
922     * continuing. Amongst other possible reasons, this is to prevent
923     * mm_release()->clear_child_tid() from writing to a user-controlled
924     * kernel address.
925     */
926    set_fs(USER_DS);
927
928    ptrace_event(PTRACE_EVENT_EXIT, code);
929
930    validate_creds_for_do_exit(tsk);
931
932    /*
933     * We're taking recursive faults here in do_exit. Safest is to just
934     * leave this task alone and wait for reboot.
935     */
936    if (unlikely(tsk->flags & PF_EXITING)) {
937        printk(KERN_ALERT
938            "Fixing recursive fault but reboot is needed!\n");
939        /*
940         * We can do this unlocked here. The futex code uses
941         * this flag just to verify whether the pi state
942         * cleanup has been done or not. In the worst case it
943         * loops once more. We pretend that the cleanup was
944         * done as there is no way to return. Either the
945         * OWNER_DIED bit is set by now or we push the blocked
946         * task into the wait for ever nirwana as well.
947         */
948        tsk->flags |= PF_EXITPIDONE;
949        set_current_state(TASK_UNINTERRUPTIBLE);
950        schedule();
951    }
952
953    exit_signals(tsk); /* sets PF_EXITING */
954    /*
955     * tsk->flags are checked in the futex code to protect against
956     * an exiting task cleaning up the robust pi futexes, and in
957     * task_work_add() to avoid the race with exit_task_work().
958     */
959    smp_mb();
960    raw_spin_unlock_wait(&tsk->pi_lock);
961
962    exit_task_work(tsk);
963
964    if (unlikely(in_atomic()))
965        printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
966                current->comm, task_pid_nr(current),
967                preempt_count());
968
969    acct_update_integrals(tsk);
970    /* sync mm's RSS info before statistics gathering */
971    if (tsk->mm)
972        sync_mm_rss(tsk->mm);
973    group_dead = atomic_dec_and_test(&tsk->signal->live);
974    if (group_dead) {
975        hrtimer_cancel(&tsk->signal->real_timer);
976        exit_itimers(tsk->signal);
977        if (tsk->mm)
978            setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
979    }
980    acct_collect(code, group_dead);
981    if (group_dead)
982        tty_audit_exit();
983    audit_free(tsk);
984
985    tsk->exit_code = code;
986    taskstats_exit(tsk, group_dead);
987
988    exit_mm(tsk);
989
990    if (group_dead)
991        acct_process();
992    trace_sched_process_exit(tsk);
993
994    exit_sem(tsk);
995    exit_shm(tsk);
996    exit_files(tsk);
997    exit_fs(tsk);
998    check_stack_usage();
999    exit_thread();
1000
1001    /*
1002     * Flush inherited counters to the parent - before the parent
1003     * gets woken up by child-exit notifications.
1004     *
1005     * because of cgroup mode, must be called before cgroup_exit()
1006     */
1007    perf_event_exit_task(tsk);
1008
1009    cgroup_exit(tsk, 1);
1010
1011    if (group_dead)
1012        disassociate_ctty(1);
1013
1014    module_put(task_thread_info(tsk)->exec_domain->module);
1015
1016    proc_exit_connector(tsk);
1017
1018    /*
1019     * FIXME: do that only when needed, using sched_exit tracepoint
1020     */
1021    ptrace_put_breakpoints(tsk);
1022
1023    exit_notify(tsk, group_dead);
1024#ifdef CONFIG_NUMA
1025    task_lock(tsk);
1026    mpol_put(tsk->mempolicy);
1027    tsk->mempolicy = NULL;
1028    task_unlock(tsk);
1029#endif
1030#ifdef CONFIG_FUTEX
1031    if (unlikely(current->pi_state_cache))
1032        kfree(current->pi_state_cache);
1033#endif
1034    /*
1035     * Make sure we are holding no locks:
1036     */
1037    debug_check_no_locks_held(tsk);
1038    /*
1039     * We can do this unlocked here. The futex code uses this flag
1040     * just to verify whether the pi state cleanup has been done
1041     * or not. In the worst case it loops once more.
1042     */
1043    tsk->flags |= PF_EXITPIDONE;
1044
1045    if (tsk->io_context)
1046        exit_io_context(tsk);
1047
1048    if (tsk->splice_pipe)
1049        __free_pipe_info(tsk->splice_pipe);
1050
1051    validate_creds_for_do_exit(tsk);
1052
1053    preempt_disable();
1054    if (tsk->nr_dirtied)
1055        __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
1056    exit_rcu();
1057
1058    /*
1059     * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
1060     * when the following two conditions become true.
1061     * - There is race condition of mmap_sem (It is acquired by
1062     * exit_mm()), and
1063     * - SMI occurs before setting TASK_RUNINNG.
1064     * (or hypervisor of virtual machine switches to other guest)
1065     * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
1066     *
1067     * To avoid it, we have to wait for releasing tsk->pi_lock which
1068     * is held by try_to_wake_up()
1069     */
1070    smp_mb();
1071    raw_spin_unlock_wait(&tsk->pi_lock);
1072
1073    /* causes final put_task_struct in finish_task_switch(). */
1074    tsk->state = TASK_DEAD;
1075    tsk->flags |= PF_NOFREEZE; /* tell freezer to ignore us */
1076    schedule();
1077    BUG();
1078    /* Avoid "noreturn function does return". */
1079    for (;;)
1080        cpu_relax(); /* For when BUG is null */
1081}
1082
1083EXPORT_SYMBOL_GPL(do_exit);
1084
1085void complete_and_exit(struct completion *comp, long code)
1086{
1087    if (comp)
1088        complete(comp);
1089
1090    do_exit(code);
1091}
1092
1093EXPORT_SYMBOL(complete_and_exit);
1094
1095SYSCALL_DEFINE1(exit, int, error_code)
1096{
1097    do_exit((error_code&0xff)<<8);
1098}
1099
1100/*
1101 * Take down every thread in the group. This is called by fatal signals
1102 * as well as by sys_exit_group (below).
1103 */
1104void
1105do_group_exit(int exit_code)
1106{
1107    struct signal_struct *sig = current->signal;
1108
1109    BUG_ON(exit_code & 0x80); /* core dumps don't get here */
1110
1111    if (signal_group_exit(sig))
1112        exit_code = sig->group_exit_code;
1113    else if (!thread_group_empty(current)) {
1114        struct sighand_struct *const sighand = current->sighand;
1115        spin_lock_irq(&sighand->siglock);
1116        if (signal_group_exit(sig))
1117            /* Another thread got here before we took the lock. */
1118            exit_code = sig->group_exit_code;
1119        else {
1120            sig->group_exit_code = exit_code;
1121            sig->flags = SIGNAL_GROUP_EXIT;
1122            zap_other_threads(current);
1123        }
1124        spin_unlock_irq(&sighand->siglock);
1125    }
1126
1127    do_exit(exit_code);
1128    /* NOTREACHED */
1129}
1130
1131/*
1132 * this kills every thread in the thread group. Note that any externally
1133 * wait4()-ing process will get the correct exit code - even if this
1134 * thread is not the thread group leader.
1135 */
1136SYSCALL_DEFINE1(exit_group, int, error_code)
1137{
1138    do_group_exit((error_code & 0xff) << 8);
1139    /* NOTREACHED */
1140    return 0;
1141}
1142
1143struct wait_opts {
1144    enum pid_type wo_type;
1145    int wo_flags;
1146    struct pid *wo_pid;
1147
1148    struct siginfo __user *wo_info;
1149    int __user *wo_stat;
1150    struct rusage __user *wo_rusage;
1151
1152    wait_queue_t child_wait;
1153    int notask_error;
1154};
1155
1156static inline
1157struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
1158{
1159    if (type != PIDTYPE_PID)
1160        task = task->group_leader;
1161    return task->pids[type].pid;
1162}
1163
1164static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1165{
1166    return wo->wo_type == PIDTYPE_MAX ||
1167        task_pid_type(p, wo->wo_type) == wo->wo_pid;
1168}
1169
1170static int eligible_child(struct wait_opts *wo, struct task_struct *p)
1171{
1172    if (!eligible_pid(wo, p))
1173        return 0;
1174    /* Wait for all children (clone and not) if __WALL is set;
1175     * otherwise, wait for clone children *only* if __WCLONE is
1176     * set; otherwise, wait for non-clone children *only*. (Note:
1177     * A "clone" child here is one that reports to its parent
1178     * using a signal other than SIGCHLD.) */
1179    if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1180        && !(wo->wo_flags & __WALL))
1181        return 0;
1182
1183    return 1;
1184}
1185
1186static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
1187                pid_t pid, uid_t uid, int why, int status)
1188{
1189    struct siginfo __user *infop;
1190    int retval = wo->wo_rusage
1191        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1192
1193    put_task_struct(p);
1194    infop = wo->wo_info;
1195    if (infop) {
1196        if (!retval)
1197            retval = put_user(SIGCHLD, &infop->si_signo);
1198        if (!retval)
1199            retval = put_user(0, &infop->si_errno);
1200        if (!retval)
1201            retval = put_user((short)why, &infop->si_code);
1202        if (!retval)
1203            retval = put_user(pid, &infop->si_pid);
1204        if (!retval)
1205            retval = put_user(uid, &infop->si_uid);
1206        if (!retval)
1207            retval = put_user(status, &infop->si_status);
1208    }
1209    if (!retval)
1210        retval = pid;
1211    return retval;
1212}
1213
1214/*
1215 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
1216 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1217 * the lock and this task is uninteresting. If we return nonzero, we have
1218 * released the lock and the system call should return.
1219 */
1220static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1221{
1222    unsigned long state;
1223    int retval, status, traced;
1224    pid_t pid = task_pid_vnr(p);
1225    uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1226    struct siginfo __user *infop;
1227
1228    if (!likely(wo->wo_flags & WEXITED))
1229        return 0;
1230
1231    if (unlikely(wo->wo_flags & WNOWAIT)) {
1232        int exit_code = p->exit_code;
1233        int why;
1234
1235        get_task_struct(p);
1236        read_unlock(&tasklist_lock);
1237        if ((exit_code & 0x7f) == 0) {
1238            why = CLD_EXITED;
1239            status = exit_code >> 8;
1240        } else {
1241            why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1242            status = exit_code & 0x7f;
1243        }
1244        return wait_noreap_copyout(wo, p, pid, uid, why, status);
1245    }
1246
1247    /*
1248     * Try to move the task's state to DEAD
1249     * only one thread is allowed to do this:
1250     */
1251    state = xchg(&p->exit_state, EXIT_DEAD);
1252    if (state != EXIT_ZOMBIE) {
1253        BUG_ON(state != EXIT_DEAD);
1254        return 0;
1255    }
1256
1257    traced = ptrace_reparented(p);
1258    /*
1259     * It can be ptraced but not reparented, check
1260     * thread_group_leader() to filter out sub-threads.
1261     */
1262    if (likely(!traced) && thread_group_leader(p)) {
1263        struct signal_struct *psig;
1264        struct signal_struct *sig;
1265        unsigned long maxrss;
1266        cputime_t tgutime, tgstime;
1267
1268        /*
1269         * The resource counters for the group leader are in its
1270         * own task_struct. Those for dead threads in the group
1271         * are in its signal_struct, as are those for the child
1272         * processes it has previously reaped. All these
1273         * accumulate in the parent's signal_struct c* fields.
1274         *
1275         * We don't bother to take a lock here to protect these
1276         * p->signal fields, because they are only touched by
1277         * __exit_signal, which runs with tasklist_lock
1278         * write-locked anyway, and so is excluded here. We do
1279         * need to protect the access to parent->signal fields,
1280         * as other threads in the parent group can be right
1281         * here reaping other children at the same time.
1282         *
1283         * We use thread_group_times() to get times for the thread
1284         * group, which consolidates times for all threads in the
1285         * group including the group leader.
1286         */
1287        thread_group_times(p, &tgutime, &tgstime);
1288        spin_lock_irq(&p->real_parent->sighand->siglock);
1289        psig = p->real_parent->signal;
1290        sig = p->signal;
1291        psig->cutime += tgutime + sig->cutime;
1292        psig->cstime += tgstime + sig->cstime;
1293        psig->cgtime += p->gtime + sig->gtime + sig->cgtime;
1294        psig->cmin_flt +=
1295            p->min_flt + sig->min_flt + sig->cmin_flt;
1296        psig->cmaj_flt +=
1297            p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1298        psig->cnvcsw +=
1299            p->nvcsw + sig->nvcsw + sig->cnvcsw;
1300        psig->cnivcsw +=
1301            p->nivcsw + sig->nivcsw + sig->cnivcsw;
1302        psig->cinblock +=
1303            task_io_get_inblock(p) +
1304            sig->inblock + sig->cinblock;
1305        psig->coublock +=
1306            task_io_get_oublock(p) +
1307            sig->oublock + sig->coublock;
1308        maxrss = max(sig->maxrss, sig->cmaxrss);
1309        if (psig->cmaxrss < maxrss)
1310            psig->cmaxrss = maxrss;
1311        task_io_accounting_add(&psig->ioac, &p->ioac);
1312        task_io_accounting_add(&psig->ioac, &sig->ioac);
1313        spin_unlock_irq(&p->real_parent->sighand->siglock);
1314    }
1315
1316    /*
1317     * Now we are sure this task is interesting, and no other
1318     * thread can reap it because we set its state to EXIT_DEAD.
1319     */
1320    read_unlock(&tasklist_lock);
1321
1322    retval = wo->wo_rusage
1323        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1324    status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1325        ? p->signal->group_exit_code : p->exit_code;
1326    if (!retval && wo->wo_stat)
1327        retval = put_user(status, wo->wo_stat);
1328
1329    infop = wo->wo_info;
1330    if (!retval && infop)
1331        retval = put_user(SIGCHLD, &infop->si_signo);
1332    if (!retval && infop)
1333        retval = put_user(0, &infop->si_errno);
1334    if (!retval && infop) {
1335        int why;
1336
1337        if ((status & 0x7f) == 0) {
1338            why = CLD_EXITED;
1339            status >>= 8;
1340        } else {
1341            why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1342            status &= 0x7f;
1343        }
1344        retval = put_user((short)why, &infop->si_code);
1345        if (!retval)
1346            retval = put_user(status, &infop->si_status);
1347    }
1348    if (!retval && infop)
1349        retval = put_user(pid, &infop->si_pid);
1350    if (!retval && infop)
1351        retval = put_user(uid, &infop->si_uid);
1352    if (!retval)
1353        retval = pid;
1354
1355    if (traced) {
1356        write_lock_irq(&tasklist_lock);
1357        /* We dropped tasklist, ptracer could die and untrace */
1358        ptrace_unlink(p);
1359        /*
1360         * If this is not a sub-thread, notify the parent.
1361         * If parent wants a zombie, don't release it now.
1362         */
1363        if (thread_group_leader(p) &&
1364            !do_notify_parent(p, p->exit_signal)) {
1365            p->exit_state = EXIT_ZOMBIE;
1366            p = NULL;
1367        }
1368        write_unlock_irq(&tasklist_lock);
1369    }
1370    if (p != NULL)
1371        release_task(p);
1372
1373    return retval;
1374}
1375
1376static int *task_stopped_code(struct task_struct *p, bool ptrace)
1377{
1378    if (ptrace) {
1379        if (task_is_stopped_or_traced(p) &&
1380            !(p->jobctl & JOBCTL_LISTENING))
1381            return &p->exit_code;
1382    } else {
1383        if (p->signal->flags & SIGNAL_STOP_STOPPED)
1384            return &p->signal->group_exit_code;
1385    }
1386    return NULL;
1387}
1388
1389/**
1390 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1391 * @wo: wait options
1392 * @ptrace: is the wait for ptrace
1393 * @p: task to wait for
1394 *
1395 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1396 *
1397 * CONTEXT:
1398 * read_lock(&tasklist_lock), which is released if return value is
1399 * non-zero. Also, grabs and releases @p->sighand->siglock.
1400 *
1401 * RETURNS:
1402 * 0 if wait condition didn't exist and search for other wait conditions
1403 * should continue. Non-zero return, -errno on failure and @p's pid on
1404 * success, implies that tasklist_lock is released and wait condition
1405 * search should terminate.
1406 */
1407static int wait_task_stopped(struct wait_opts *wo,
1408                int ptrace, struct task_struct *p)
1409{
1410    struct siginfo __user *infop;
1411    int retval, exit_code, *p_code, why;
1412    uid_t uid = 0; /* unneeded, required by compiler */
1413    pid_t pid;
1414
1415    /*
1416     * Traditionally we see ptrace'd stopped tasks regardless of options.
1417     */
1418    if (!ptrace && !(wo->wo_flags & WUNTRACED))
1419        return 0;
1420
1421    if (!task_stopped_code(p, ptrace))
1422        return 0;
1423
1424    exit_code = 0;
1425    spin_lock_irq(&p->sighand->siglock);
1426
1427    p_code = task_stopped_code(p, ptrace);
1428    if (unlikely(!p_code))
1429        goto unlock_sig;
1430
1431    exit_code = *p_code;
1432    if (!exit_code)
1433        goto unlock_sig;
1434
1435    if (!unlikely(wo->wo_flags & WNOWAIT))
1436        *p_code = 0;
1437
1438    uid = from_kuid_munged(current_user_ns(), task_uid(p));
1439unlock_sig:
1440    spin_unlock_irq(&p->sighand->siglock);
1441    if (!exit_code)
1442        return 0;
1443
1444    /*
1445     * Now we are pretty sure this task is interesting.
1446     * Make sure it doesn't get reaped out from under us while we
1447     * give up the lock and then examine it below. We don't want to
1448     * keep holding onto the tasklist_lock while we call getrusage and
1449     * possibly take page faults for user memory.
1450     */
1451    get_task_struct(p);
1452    pid = task_pid_vnr(p);
1453    why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1454    read_unlock(&tasklist_lock);
1455
1456    if (unlikely(wo->wo_flags & WNOWAIT))
1457        return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1458
1459    retval = wo->wo_rusage
1460        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1461    if (!retval && wo->wo_stat)
1462        retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1463
1464    infop = wo->wo_info;
1465    if (!retval && infop)
1466        retval = put_user(SIGCHLD, &infop->si_signo);
1467    if (!retval && infop)
1468        retval = put_user(0, &infop->si_errno);
1469    if (!retval && infop)
1470        retval = put_user((short)why, &infop->si_code);
1471    if (!retval && infop)
1472        retval = put_user(exit_code, &infop->si_status);
1473    if (!retval && infop)
1474        retval = put_user(pid, &infop->si_pid);
1475    if (!retval && infop)
1476        retval = put_user(uid, &infop->si_uid);
1477    if (!retval)
1478        retval = pid;
1479    put_task_struct(p);
1480
1481    BUG_ON(!retval);
1482    return retval;
1483}
1484
1485/*
1486 * Handle do_wait work for one task in a live, non-stopped state.
1487 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1488 * the lock and this task is uninteresting. If we return nonzero, we have
1489 * released the lock and the system call should return.
1490 */
1491static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1492{
1493    int retval;
1494    pid_t pid;
1495    uid_t uid;
1496
1497    if (!unlikely(wo->wo_flags & WCONTINUED))
1498        return 0;
1499
1500    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1501        return 0;
1502
1503    spin_lock_irq(&p->sighand->siglock);
1504    /* Re-check with the lock held. */
1505    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1506        spin_unlock_irq(&p->sighand->siglock);
1507        return 0;
1508    }
1509    if (!unlikely(wo->wo_flags & WNOWAIT))
1510        p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1511    uid = from_kuid_munged(current_user_ns(), task_uid(p));
1512    spin_unlock_irq(&p->sighand->siglock);
1513
1514    pid = task_pid_vnr(p);
1515    get_task_struct(p);
1516    read_unlock(&tasklist_lock);
1517
1518    if (!wo->wo_info) {
1519        retval = wo->wo_rusage
1520            ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1521        put_task_struct(p);
1522        if (!retval && wo->wo_stat)
1523            retval = put_user(0xffff, wo->wo_stat);
1524        if (!retval)
1525            retval = pid;
1526    } else {
1527        retval = wait_noreap_copyout(wo, p, pid, uid,
1528                         CLD_CONTINUED, SIGCONT);
1529        BUG_ON(retval == 0);
1530    }
1531
1532    return retval;
1533}
1534
1535/*
1536 * Consider @p for a wait by @parent.
1537 *
1538 * -ECHILD should be in ->notask_error before the first call.
1539 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1540 * Returns zero if the search for a child should continue;
1541 * then ->notask_error is 0 if @p is an eligible child,
1542 * or another error from security_task_wait(), or still -ECHILD.
1543 */
1544static int wait_consider_task(struct wait_opts *wo, int ptrace,
1545                struct task_struct *p)
1546{
1547    int ret = eligible_child(wo, p);
1548    if (!ret)
1549        return ret;
1550
1551    ret = security_task_wait(p);
1552    if (unlikely(ret < 0)) {
1553        /*
1554         * If we have not yet seen any eligible child,
1555         * then let this error code replace -ECHILD.
1556         * A permission error will give the user a clue
1557         * to look for security policy problems, rather
1558         * than for mysterious wait bugs.
1559         */
1560        if (wo->notask_error)
1561            wo->notask_error = ret;
1562        return 0;
1563    }
1564
1565    /* dead body doesn't have much to contribute */
1566    if (unlikely(p->exit_state == EXIT_DEAD)) {
1567        /*
1568         * But do not ignore this task until the tracer does
1569         * wait_task_zombie()->do_notify_parent().
1570         */
1571        if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
1572            wo->notask_error = 0;
1573        return 0;
1574    }
1575
1576    /* slay zombie? */
1577    if (p->exit_state == EXIT_ZOMBIE) {
1578        /*
1579         * A zombie ptracee is only visible to its ptracer.
1580         * Notification and reaping will be cascaded to the real
1581         * parent when the ptracer detaches.
1582         */
1583        if (likely(!ptrace) && unlikely(p->ptrace)) {
1584            /* it will become visible, clear notask_error */
1585            wo->notask_error = 0;
1586            return 0;
1587        }
1588
1589        /* we don't reap group leaders with subthreads */
1590        if (!delay_group_leader(p))
1591            return wait_task_zombie(wo, p);
1592
1593        /*
1594         * Allow access to stopped/continued state via zombie by
1595         * falling through. Clearing of notask_error is complex.
1596         *
1597         * When !@ptrace:
1598         *
1599         * If WEXITED is set, notask_error should naturally be
1600         * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1601         * so, if there are live subthreads, there are events to
1602         * wait for. If all subthreads are dead, it's still safe
1603         * to clear - this function will be called again in finite
1604         * amount time once all the subthreads are released and
1605         * will then return without clearing.
1606         *
1607         * When @ptrace:
1608         *
1609         * Stopped state is per-task and thus can't change once the
1610         * target task dies. Only continued and exited can happen.
1611         * Clear notask_error if WCONTINUED | WEXITED.
1612         */
1613        if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1614            wo->notask_error = 0;
1615    } else {
1616        /*
1617         * If @p is ptraced by a task in its real parent's group,
1618         * hide group stop/continued state when looking at @p as
1619         * the real parent; otherwise, a single stop can be
1620         * reported twice as group and ptrace stops.
1621         *
1622         * If a ptracer wants to distinguish the two events for its
1623         * own children, it should create a separate process which
1624         * takes the role of real parent.
1625         */
1626        if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
1627            return 0;
1628
1629        /*
1630         * @p is alive and it's gonna stop, continue or exit, so
1631         * there always is something to wait for.
1632         */
1633        wo->notask_error = 0;
1634    }
1635
1636    /*
1637     * Wait for stopped. Depending on @ptrace, different stopped state
1638     * is used and the two don't interact with each other.
1639     */
1640    ret = wait_task_stopped(wo, ptrace, p);
1641    if (ret)
1642        return ret;
1643
1644    /*
1645     * Wait for continued. There's only one continued state and the
1646     * ptracer can consume it which can confuse the real parent. Don't
1647     * use WCONTINUED from ptracer. You don't need or want it.
1648     */
1649    return wait_task_continued(wo, p);
1650}
1651
1652/*
1653 * Do the work of do_wait() for one thread in the group, @tsk.
1654 *
1655 * -ECHILD should be in ->notask_error before the first call.
1656 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1657 * Returns zero if the search for a child should continue; then
1658 * ->notask_error is 0 if there were any eligible children,
1659 * or another error from security_task_wait(), or still -ECHILD.
1660 */
1661static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1662{
1663    struct task_struct *p;
1664
1665    list_for_each_entry(p, &tsk->children, sibling) {
1666        int ret = wait_consider_task(wo, 0, p);
1667        if (ret)
1668            return ret;
1669    }
1670
1671    return 0;
1672}
1673
1674static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1675{
1676    struct task_struct *p;
1677
1678    list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1679        int ret = wait_consider_task(wo, 1, p);
1680        if (ret)
1681            return ret;
1682    }
1683
1684    return 0;
1685}
1686
1687static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1688                int sync, void *key)
1689{
1690    struct wait_opts *wo = container_of(wait, struct wait_opts,
1691                        child_wait);
1692    struct task_struct *p = key;
1693
1694    if (!eligible_pid(wo, p))
1695        return 0;
1696
1697    if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1698        return 0;
1699
1700    return default_wake_function(wait, mode, sync, key);
1701}
1702
1703void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1704{
1705    __wake_up_sync_key(&parent->signal->wait_chldexit,
1706                TASK_INTERRUPTIBLE, 1, p);
1707}
1708
1709static long do_wait(struct wait_opts *wo)
1710{
1711    struct task_struct *tsk;
1712    int retval;
1713
1714    trace_sched_process_wait(wo->wo_pid);
1715
1716    init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1717    wo->child_wait.private = current;
1718    add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1719repeat:
1720    /*
1721     * If there is nothing that can match our critiera just get out.
1722     * We will clear ->notask_error to zero if we see any child that
1723     * might later match our criteria, even if we are not able to reap
1724     * it yet.
1725     */
1726    wo->notask_error = -ECHILD;
1727    if ((wo->wo_type < PIDTYPE_MAX) &&
1728       (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1729        goto notask;
1730
1731    set_current_state(TASK_INTERRUPTIBLE);
1732    read_lock(&tasklist_lock);
1733    tsk = current;
1734    do {
1735        retval = do_wait_thread(wo, tsk);
1736        if (retval)
1737            goto end;
1738
1739        retval = ptrace_do_wait(wo, tsk);
1740        if (retval)
1741            goto end;
1742
1743        if (wo->wo_flags & __WNOTHREAD)
1744            break;
1745    } while_each_thread(current, tsk);
1746    read_unlock(&tasklist_lock);
1747
1748notask:
1749    retval = wo->notask_error;
1750    if (!retval && !(wo->wo_flags & WNOHANG)) {
1751        retval = -ERESTARTSYS;
1752        if (!signal_pending(current)) {
1753            schedule();
1754            goto repeat;
1755        }
1756    }
1757end:
1758    __set_current_state(TASK_RUNNING);
1759    remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1760    return retval;
1761}
1762
1763SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1764        infop, int, options, struct rusage __user *, ru)
1765{
1766    struct wait_opts wo;
1767    struct pid *pid = NULL;
1768    enum pid_type type;
1769    long ret;
1770
1771    if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
1772        return -EINVAL;
1773    if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1774        return -EINVAL;
1775
1776    switch (which) {
1777    case P_ALL:
1778        type = PIDTYPE_MAX;
1779        break;
1780    case P_PID:
1781        type = PIDTYPE_PID;
1782        if (upid <= 0)
1783            return -EINVAL;
1784        break;
1785    case P_PGID:
1786        type = PIDTYPE_PGID;
1787        if (upid <= 0)
1788            return -EINVAL;
1789        break;
1790    default:
1791        return -EINVAL;
1792    }
1793
1794    if (type < PIDTYPE_MAX)
1795        pid = find_get_pid(upid);
1796
1797    wo.wo_type = type;
1798    wo.wo_pid = pid;
1799    wo.wo_flags = options;
1800    wo.wo_info = infop;
1801    wo.wo_stat = NULL;
1802    wo.wo_rusage = ru;
1803    ret = do_wait(&wo);
1804
1805    if (ret > 0) {
1806        ret = 0;
1807    } else if (infop) {
1808        /*
1809         * For a WNOHANG return, clear out all the fields
1810         * we would set so the user can easily tell the
1811         * difference.
1812         */
1813        if (!ret)
1814            ret = put_user(0, &infop->si_signo);
1815        if (!ret)
1816            ret = put_user(0, &infop->si_errno);
1817        if (!ret)
1818            ret = put_user(0, &infop->si_code);
1819        if (!ret)
1820            ret = put_user(0, &infop->si_pid);
1821        if (!ret)
1822            ret = put_user(0, &infop->si_uid);
1823        if (!ret)
1824            ret = put_user(0, &infop->si_status);
1825    }
1826
1827    put_pid(pid);
1828
1829    /* avoid REGPARM breakage on x86: */
1830    asmlinkage_protect(5, ret, which, upid, infop, options, ru);
1831    return ret;
1832}
1833
1834SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1835        int, options, struct rusage __user *, ru)
1836{
1837    struct wait_opts wo;
1838    struct pid *pid = NULL;
1839    enum pid_type type;
1840    long ret;
1841
1842    if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1843            __WNOTHREAD|__WCLONE|__WALL))
1844        return -EINVAL;
1845
1846    if (upid == -1)
1847        type = PIDTYPE_MAX;
1848    else if (upid < 0) {
1849        type = PIDTYPE_PGID;
1850        pid = find_get_pid(-upid);
1851    } else if (upid == 0) {
1852        type = PIDTYPE_PGID;
1853        pid = get_task_pid(current, PIDTYPE_PGID);
1854    } else /* upid > 0 */ {
1855        type = PIDTYPE_PID;
1856        pid = find_get_pid(upid);
1857    }
1858
1859    wo.wo_type = type;
1860    wo.wo_pid = pid;
1861    wo.wo_flags = options | WEXITED;
1862    wo.wo_info = NULL;
1863    wo.wo_stat = stat_addr;
1864    wo.wo_rusage = ru;
1865    ret = do_wait(&wo);
1866    put_pid(pid);
1867
1868    /* avoid REGPARM breakage on x86: */
1869    asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
1870    return ret;
1871}
1872
1873#ifdef __ARCH_WANT_SYS_WAITPID
1874
1875/*
1876 * sys_waitpid() remains for compatibility. waitpid() should be
1877 * implemented by calling sys_wait4() from libc.a.
1878 */
1879SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1880{
1881    return sys_wait4(pid, stat_addr, options, NULL);
1882}
1883
1884#endif
1885

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