exit.c

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/*
 *  linux/kernel/exit.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/iocontext.h>
#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/binfmts.h>
#include <linux/nsproxy.h>
#include <linux/pid_namespace.h>
#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
#include <linux/kthread.h>
#include <linux/mempolicy.h>
#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/freezer.h>
#include <linux/cgroup.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/posix-timers.h>
#include <linux/cn_proc.h>
#include <linux/mutex.h>
#include <linux/futex.h>
#include <linux/pipe_fs_i.h>
#include <linux/audit.h> /* for audit_free() */
#include <linux/resource.h>
#include <linux/blkdev.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/tracehook.h>
#include <linux/fs_struct.h>
#include <linux/init_task.h>
#include <linux/perf_event.h>
#include <trace/events/sched.h>
#include <linux/hw_breakpoint.h>
#include <linux/oom.h>
#include <linux/writeback.h>
#include <linux/shm.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

static void exit_mm(struct task_struct * tsk);

static void __unhash_process(struct task_struct *p, bool group_dead)
{
    nr_threads--;
    detach_pid(p, PIDTYPE_PID);
    if (group_dead) {
        detach_pid(p, PIDTYPE_PGID);
        detach_pid(p, PIDTYPE_SID);

        list_del_rcu(&p->tasks);
        list_del_init(&p->sibling);
        __this_cpu_dec(process_counts);
        /*
         * If we are the last child process in a pid namespace to be
         * reaped, notify the reaper sleeping zap_pid_ns_processes().
         */
        if (IS_ENABLED(CONFIG_PID_NS)) {
            struct task_struct *parent = p->real_parent;

            if ((task_active_pid_ns(parent)->child_reaper == parent) &&
                list_empty(&parent->children) &&
                (parent->flags & PF_EXITING))
                wake_up_process(parent);
        }
    }
    list_del_rcu(&p->thread_group);
}

/*
 * This function expects the tasklist_lock write-locked.
 */
static void __exit_signal(struct task_struct *tsk)
{
    struct signal_struct *sig = tsk->signal;
    bool group_dead = thread_group_leader(tsk);
    struct sighand_struct *sighand;
    struct tty_struct *uninitialized_var(tty);

    sighand = rcu_dereference_check(tsk->sighand,
                    lockdep_tasklist_lock_is_held());
    spin_lock(&sighand->siglock);

    posix_cpu_timers_exit(tsk);
    if (group_dead) {
        posix_cpu_timers_exit_group(tsk);
        tty = sig->tty;
        sig->tty = NULL;
    } else {
        /*
         * This can only happen if the caller is de_thread().
         * FIXME: this is the temporary hack, we should teach
         * posix-cpu-timers to handle this case correctly.
         */
        if (unlikely(has_group_leader_pid(tsk)))
            posix_cpu_timers_exit_group(tsk);

        /*
         * If there is any task waiting for the group exit
         * then notify it:
         */
        if (sig->notify_count > 0 && !--sig->notify_count)
            wake_up_process(sig->group_exit_task);

        if (tsk == sig->curr_target)
            sig->curr_target = next_thread(tsk);
        /*
         * Accumulate here the counters for all threads but the
         * group leader as they die, so they can be added into
         * the process-wide totals when those are taken.
         * The group leader stays around as a zombie as long
         * as there are other threads.  When it gets reaped,
         * the exit.c code will add its counts into these totals.
         * We won't ever get here for the group leader, since it
         * will have been the last reference on the signal_struct.
         */
        sig->utime += tsk->utime;
        sig->stime += tsk->stime;
        sig->gtime += tsk->gtime;
        sig->min_flt += tsk->min_flt;
        sig->maj_flt += tsk->maj_flt;
        sig->nvcsw += tsk->nvcsw;
        sig->nivcsw += tsk->nivcsw;
        sig->inblock += task_io_get_inblock(tsk);
        sig->oublock += task_io_get_oublock(tsk);
        task_io_accounting_add(&sig->ioac, &tsk->ioac);
        sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
    }

    sig->nr_threads--;
    __unhash_process(tsk, group_dead);

    /*
     * Do this under ->siglock, we can race with another thread
     * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
     */
    flush_sigqueue(&tsk->pending);
    tsk->sighand = NULL;
    spin_unlock(&sighand->siglock);

    __cleanup_sighand(sighand);
    clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
    if (group_dead) {
        flush_sigqueue(&sig->shared_pending);
        tty_kref_put(tty);
    }
}

static void delayed_put_task_struct(struct rcu_head *rhp)
{
    struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);

    perf_event_delayed_put(tsk);
    trace_sched_process_free(tsk);
    put_task_struct(tsk);
}


void release_task(struct task_struct * p)
{
    struct task_struct *leader;
    int zap_leader;
repeat:
    /* don't need to get the RCU readlock here - the process is dead and
     * can't be modifying its own credentials. But shut RCU-lockdep up */
    rcu_read_lock();
    atomic_dec(&__task_cred(p)->user->processes);
    rcu_read_unlock();

    proc_flush_task(p);

    write_lock_irq(&tasklist_lock);
    ptrace_release_task(p);
    __exit_signal(p);

    /*
     * If we are the last non-leader member of the thread
     * group, and the leader is zombie, then notify the
     * group leader's parent process. (if it wants notification.)
     */
    zap_leader = 0;
    leader = p->group_leader;
    if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
        /*
         * If we were the last child thread and the leader has
         * exited already, and the leader's parent ignores SIGCHLD,
         * then we are the one who should release the leader.
         */
        zap_leader = do_notify_parent(leader, leader->exit_signal);
        if (zap_leader)
            leader->exit_state = EXIT_DEAD;
    }

    write_unlock_irq(&tasklist_lock);
    release_thread(p);
    call_rcu(&p->rcu, delayed_put_task_struct);

    p = leader;
    if (unlikely(zap_leader))
        goto repeat;
}

/*
 * This checks not only the pgrp, but falls back on the pid if no
 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 * without this...
 *
 * The caller must hold rcu lock or the tasklist lock.
 */
struct pid *session_of_pgrp(struct pid *pgrp)
{
    struct task_struct *p;
    struct pid *sid = NULL;

    p = pid_task(pgrp, PIDTYPE_PGID);
    if (p == NULL)
        p = pid_task(pgrp, PIDTYPE_PID);
    if (p != NULL)
        sid = task_session(p);

    return sid;
}

/*
 * Determine if a process group is "orphaned", according to the POSIX
 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 * by terminal-generated stop signals.  Newly orphaned process groups are
 * to receive a SIGHUP and a SIGCONT.
 *
 * "I ask you, have you ever known what it is to be an orphan?"
 */
static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
{
    struct task_struct *p;

    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
        if ((p == ignored_task) ||
            (p->exit_state && thread_group_empty(p)) ||
            is_global_init(p->real_parent))
            continue;

        if (task_pgrp(p->real_parent) != pgrp &&
            task_session(p->real_parent) == task_session(p))
            return 0;
    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);

    return 1;
}

int is_current_pgrp_orphaned(void)
{
    int retval;

    read_lock(&tasklist_lock);
    retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
    read_unlock(&tasklist_lock);

    return retval;
}

static bool has_stopped_jobs(struct pid *pgrp)
{
    struct task_struct *p;

    do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
        if (p->signal->flags & SIGNAL_STOP_STOPPED)
            return true;
    } while_each_pid_task(pgrp, PIDTYPE_PGID, p);

    return false;
}

/*
 * Check to see if any process groups have become orphaned as
 * a result of our exiting, and if they have any stopped jobs,
 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 */
static void
kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
{
    struct pid *pgrp = task_pgrp(tsk);
    struct task_struct *ignored_task = tsk;

    if (!parent)
         /* exit: our father is in a different pgrp than
          * we are and we were the only connection outside.
          */
        parent = tsk->real_parent;
    else
        /* reparent: our child is in a different pgrp than
         * we are, and it was the only connection outside.
         */
        ignored_task = NULL;

    if (task_pgrp(parent) != pgrp &&
        task_session(parent) == task_session(tsk) &&
        will_become_orphaned_pgrp(pgrp, ignored_task) &&
        has_stopped_jobs(pgrp)) {
        __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
        __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
    }
}

static void reparent_to_kthreadd(void)
{
    write_lock_irq(&tasklist_lock);

    ptrace_unlink(current);
    /* Reparent to init */
    current->real_parent = current->parent = kthreadd_task;
    list_move_tail(&current->sibling, &current->real_parent->children);

    /* Set the exit signal to SIGCHLD so we signal init on exit */
    current->exit_signal = SIGCHLD;

    if (task_nice(current) < 0)
        set_user_nice(current, 0);
    /* cpus_allowed? */
    /* rt_priority? */
    /* signals? */
    memcpy(current->signal->rlim, init_task.signal->rlim,
           sizeof(current->signal->rlim));

    atomic_inc(&init_cred.usage);
    commit_creds(&init_cred);
    write_unlock_irq(&tasklist_lock);
}

void __set_special_pids(struct pid *pid)
{
    struct task_struct *curr = current->group_leader;

    if (task_session(curr) != pid)
        change_pid(curr, PIDTYPE_SID, pid);

    if (task_pgrp(curr) != pid)
        change_pid(curr, PIDTYPE_PGID, pid);
}

static void set_special_pids(struct pid *pid)
{
    write_lock_irq(&tasklist_lock);
    __set_special_pids(pid);
    write_unlock_irq(&tasklist_lock);
}

/*
 * Let kernel threads use this to say that they allow a certain signal.
 * Must not be used if kthread was cloned with CLONE_SIGHAND.
 */
int allow_signal(int sig)
{
    if (!valid_signal(sig) || sig < 1)
        return -EINVAL;

    spin_lock_irq(&current->sighand->siglock);
    /* This is only needed for daemonize()'ed kthreads */
    sigdelset(&current->blocked, sig);
    /*
     * Kernel threads handle their own signals. Let the signal code
     * know it'll be handled, so that they don't get converted to
     * SIGKILL or just silently dropped.
     */
    current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
    recalc_sigpending();
    spin_unlock_irq(&current->sighand->siglock);
    return 0;
}

EXPORT_SYMBOL(allow_signal);

int disallow_signal(int sig)
{
    if (!valid_signal(sig) || sig < 1)
        return -EINVAL;

    spin_lock_irq(&current->sighand->siglock);
    current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
    recalc_sigpending();
    spin_unlock_irq(&current->sighand->siglock);
    return 0;
}

EXPORT_SYMBOL(disallow_signal);

/*
 *  Put all the gunge required to become a kernel thread without
 *  attached user resources in one place where it belongs.
 */

void daemonize(const char *name, ...)
{
    va_list args;
    sigset_t blocked;

    va_start(args, name);
    vsnprintf(current->comm, sizeof(current->comm), name, args);
    va_end(args);

    /*
     * If we were started as result of loading a module, close all of the
     * user space pages.  We don't need them, and if we didn't close them
     * they would be locked into memory.
     */
    exit_mm(current);
    /*
     * We don't want to get frozen, in case system-wide hibernation
     * or suspend transition begins right now.
     */
    current->flags |= (PF_NOFREEZE | PF_KTHREAD);

    if (current->nsproxy != &init_nsproxy) {
        get_nsproxy(&init_nsproxy);
        switch_task_namespaces(current, &init_nsproxy);
    }
    set_special_pids(&init_struct_pid);
    proc_clear_tty(current);

    /* Block and flush all signals */
    sigfillset(&blocked);
    sigprocmask(SIG_BLOCK, &blocked, NULL);
    flush_signals(current);

    /* Become as one with the init task */

    daemonize_fs_struct();
    daemonize_descriptors();

    reparent_to_kthreadd();
}

EXPORT_SYMBOL(daemonize);

#ifdef CONFIG_MM_OWNER
/*
 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 */
void mm_update_next_owner(struct mm_struct *mm)
{
    struct task_struct *c, *g, *p = current;

retry:
    /*
     * If the exiting or execing task is not the owner, it's
     * someone else's problem.
     */
    if (mm->owner != p)
        return;
    /*
     * The current owner is exiting/execing and there are no other
     * candidates.  Do not leave the mm pointing to a possibly
     * freed task structure.
     */
    if (atomic_read(&mm->mm_users) <= 1) {
        mm->owner = NULL;
        return;
    }

    read_lock(&tasklist_lock);
    /*
     * Search in the children
     */
    list_for_each_entry(c, &p->children, sibling) {
        if (c->mm == mm)
            goto assign_new_owner;
    }

    /*
     * Search in the siblings
     */
    list_for_each_entry(c, &p->real_parent->children, sibling) {
        if (c->mm == mm)
            goto assign_new_owner;
    }

    /*
     * Search through everything else. We should not get
     * here often
     */
    do_each_thread(g, c) {
        if (c->mm == mm)
            goto assign_new_owner;
    } while_each_thread(g, c);

    read_unlock(&tasklist_lock);
    /*
     * We found no owner yet mm_users > 1: this implies that we are
     * most likely racing with swapoff (try_to_unuse()) or /proc or
     * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
     */
    mm->owner = NULL;
    return;

assign_new_owner:
    BUG_ON(c == p);
    get_task_struct(c);
    /*
     * The task_lock protects c->mm from changing.
     * We always want mm->owner->mm == mm
     */
    task_lock(c);
    /*
     * Delay read_unlock() till we have the task_lock()
     * to ensure that c does not slip away underneath us
     */
    read_unlock(&tasklist_lock);
    if (c->mm != mm) {
        task_unlock(c);
        put_task_struct(c);
        goto retry;
    }
    mm->owner = c;
    task_unlock(c);
    put_task_struct(c);
}
#endif /* CONFIG_MM_OWNER */

/*
 * Turn us into a lazy TLB process if we
 * aren't already..
 */
static void exit_mm(struct task_struct * tsk)
{
    struct mm_struct *mm = tsk->mm;
    struct core_state *core_state;

    mm_release(tsk, mm);
    if (!mm)
        return;
    sync_mm_rss(mm);
    /*
     * Serialize with any possible pending coredump.
     * We must hold mmap_sem around checking core_state
     * and clearing tsk->mm.  The core-inducing thread
     * will increment ->nr_threads for each thread in the
     * group with ->mm != NULL.
     */
    down_read(&mm->mmap_sem);
    core_state = mm->core_state;
    if (core_state) {
        struct core_thread self;
        up_read(&mm->mmap_sem);

        self.task = tsk;
        self.next = xchg(&core_state->dumper.next, &self);
        /*
         * Implies mb(), the result of xchg() must be visible
         * to core_state->dumper.
         */
        if (atomic_dec_and_test(&core_state->nr_threads))
            complete(&core_state->startup);

        for (;;) {
            set_task_state(tsk, TASK_UNINTERRUPTIBLE);
            if (!self.task) /* see coredump_finish() */
                break;
            schedule();
        }
        __set_task_state(tsk, TASK_RUNNING);
        down_read(&mm->mmap_sem);
    }
    atomic_inc(&mm->mm_count);
    BUG_ON(mm != tsk->active_mm);
    /* more a memory barrier than a real lock */
    task_lock(tsk);
    tsk->mm = NULL;
    up_read(&mm->mmap_sem);
    enter_lazy_tlb(mm, current);
    task_unlock(tsk);
    mm_update_next_owner(mm);
    mmput(mm);
}

/*
 * When we die, we re-parent all our children, and try to:
 * 1. give them to another thread in our thread group, if such a member exists
 * 2. give it to the first ancestor process which prctl'd itself as a
 *    child_subreaper for its children (like a service manager)
 * 3. give it to the init process (PID 1) in our pid namespace
 */
static struct task_struct *find_new_reaper(struct task_struct *father)
    __releases(&tasklist_lock)
    __acquires(&tasklist_lock)
{
    struct pid_namespace *pid_ns = task_active_pid_ns(father);
    struct task_struct *thread;

    thread = father;
    while_each_thread(father, thread) {
        if (thread->flags & PF_EXITING)
            continue;
        if (unlikely(pid_ns->child_reaper == father))
            pid_ns->child_reaper = thread;
        return thread;
    }

    if (unlikely(pid_ns->child_reaper == father)) {
        write_unlock_irq(&tasklist_lock);
        if (unlikely(pid_ns == &init_pid_ns)) {
            panic("Attempted to kill init! exitcode=0x%08x\n",
                father->signal->group_exit_code ?:
                    father->exit_code);
        }

        zap_pid_ns_processes(pid_ns);
        write_lock_irq(&tasklist_lock);
    } else if (father->signal->has_child_subreaper) {
        struct task_struct *reaper;

        /*
         * Find the first ancestor marked as child_subreaper.
         * Note that the code below checks same_thread_group(reaper,
         * pid_ns->child_reaper).  This is what we need to DTRT in a
         * PID namespace. However we still need the check above, see
         * http://marc.info/?l=linux-kernel&m=131385460420380
         */
        for (reaper = father->real_parent;
             reaper != &init_task;
             reaper = reaper->real_parent) {
            if (same_thread_group(reaper, pid_ns->child_reaper))
                break;
            if (!reaper->signal->is_child_subreaper)
                continue;
            thread = reaper;
            do {
                if (!(thread->flags & PF_EXITING))
                    return reaper;
            } while_each_thread(reaper, thread);
        }
    }

    return pid_ns->child_reaper;
}

/*
* Any that need to be release_task'd are put on the @dead list.
 */
static void reparent_leader(struct task_struct *father, struct task_struct *p,
                struct list_head *dead)
{
    list_move_tail(&p->sibling, &p->real_parent->children);

    if (p->exit_state == EXIT_DEAD)
        return;
    /*
     * If this is a threaded reparent there is no need to
     * notify anyone anything has happened.
     */
    if (same_thread_group(p->real_parent, father))
        return;

    /* We don't want people slaying init.  */
    p->exit_signal = SIGCHLD;

    /* If it has exited notify the new parent about this child's death. */
    if (!p->ptrace &&
        p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
        if (do_notify_parent(p, p->exit_signal)) {
            p->exit_state = EXIT_DEAD;
            list_move_tail(&p->sibling, dead);
        }
    }

    kill_orphaned_pgrp(p, father);
}

static void forget_original_parent(struct task_struct *father)
{
    struct task_struct *p, *n, *reaper;
    LIST_HEAD(dead_children);

    write_lock_irq(&tasklist_lock);
    /*
     * Note that exit_ptrace() and find_new_reaper() might
     * drop tasklist_lock and reacquire it.
     */
    exit_ptrace(father);
    reaper = find_new_reaper(father);

    list_for_each_entry_safe(p, n, &father->children, sibling) {
        struct task_struct *t = p;
        do {
            t->real_parent = reaper;
            if (t->parent == father) {
                BUG_ON(t->ptrace);
                t->parent = t->real_parent;
            }
            if (t->pdeath_signal)
                group_send_sig_info(t->pdeath_signal,
                            SEND_SIG_NOINFO, t);
        } while_each_thread(p, t);
        reparent_leader(father, p, &dead_children);
    }
    write_unlock_irq(&tasklist_lock);

    BUG_ON(!list_empty(&father->children));

    list_for_each_entry_safe(p, n, &dead_children, sibling) {
        list_del_init(&p->sibling);
        release_task(p);
    }
}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
static void exit_notify(struct task_struct *tsk, int group_dead)
{
    bool autoreap;

    /*
     * This does two things:
     *
     * A.  Make init inherit all the child processes
     * B.  Check to see if any process groups have become orphaned
     *  as a result of our exiting, and if they have any stopped
     *  jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
     */
    forget_original_parent(tsk);
    exit_task_namespaces(tsk);

    write_lock_irq(&tasklist_lock);
    if (group_dead)
        kill_orphaned_pgrp(tsk->group_leader, NULL);

    if (unlikely(tsk->ptrace)) {
        int sig = thread_group_leader(tsk) &&
                thread_group_empty(tsk) &&
                !ptrace_reparented(tsk) ?
            tsk->exit_signal : SIGCHLD;
        autoreap = do_notify_parent(tsk, sig);
    } else if (thread_group_leader(tsk)) {
        autoreap = thread_group_empty(tsk) &&
            do_notify_parent(tsk, tsk->exit_signal);
    } else {
        autoreap = true;
    }

    tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;

    /* mt-exec, de_thread() is waiting for group leader */
    if (unlikely(tsk->signal->notify_count < 0))
        wake_up_process(tsk->signal->group_exit_task);
    write_unlock_irq(&tasklist_lock);

    /* If the process is dead, release it - nobody will wait for it */
    if (autoreap)
        release_task(tsk);
}

#ifdef CONFIG_DEBUG_STACK_USAGE
static void check_stack_usage(void)
{
    static DEFINE_SPINLOCK(low_water_lock);
    static int lowest_to_date = THREAD_SIZE;
    unsigned long free;

    free = stack_not_used(current);

    if (free >= lowest_to_date)
        return;

    spin_lock(&low_water_lock);
    if (free < lowest_to_date) {
        printk(KERN_WARNING "%s (%d) used greatest stack depth: "
                "%lu bytes left\n",
                current->comm, task_pid_nr(current), free);
        lowest_to_date = free;
    }
    spin_unlock(&low_water_lock);
}
#else
static inline void check_stack_usage(void) {}
#endif

void do_exit(long code)
{
    struct task_struct *tsk = current;
    int group_dead;

    profile_task_exit(tsk);

    WARN_ON(blk_needs_flush_plug(tsk));

    if (unlikely(in_interrupt()))
        panic("Aiee, killing interrupt handler!");
    if (unlikely(!tsk->pid))
        panic("Attempted to kill the idle task!");

    /*
     * If do_exit is called because this processes oopsed, it's possible
     * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
     * continuing. Amongst other possible reasons, this is to prevent
     * mm_release()->clear_child_tid() from writing to a user-controlled
     * kernel address.
     */
    set_fs(USER_DS);

    ptrace_event(PTRACE_EVENT_EXIT, code);

    validate_creds_for_do_exit(tsk);

    /*
     * We're taking recursive faults here in do_exit. Safest is to just
     * leave this task alone and wait for reboot.
     */
    if (unlikely(tsk->flags & PF_EXITING)) {
        printk(KERN_ALERT
            "Fixing recursive fault but reboot is needed!\n");
        /*
         * We can do this unlocked here. The futex code uses
         * this flag just to verify whether the pi state
         * cleanup has been done or not. In the worst case it
         * loops once more. We pretend that the cleanup was
         * done as there is no way to return. Either the
         * OWNER_DIED bit is set by now or we push the blocked
         * task into the wait for ever nirwana as well.
         */
        tsk->flags |= PF_EXITPIDONE;
        set_current_state(TASK_UNINTERRUPTIBLE);
        schedule();
    }

    exit_signals(tsk);  /* sets PF_EXITING */
    /*
     * tsk->flags are checked in the futex code to protect against
     * an exiting task cleaning up the robust pi futexes.
     */
    smp_mb();
    raw_spin_unlock_wait(&tsk->pi_lock);

    if (unlikely(in_atomic()))
        printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
                current->comm, task_pid_nr(current),
                preempt_count());

    acct_update_integrals(tsk);
    /* sync mm's RSS info before statistics gathering */
    if (tsk->mm)
        sync_mm_rss(tsk->mm);
    group_dead = atomic_dec_and_test(&tsk->signal->live);
    if (group_dead) {
        hrtimer_cancel(&tsk->signal->real_timer);
        exit_itimers(tsk->signal);
        if (tsk->mm)
            setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
    }
    acct_collect(code, group_dead);
    if (group_dead)
        tty_audit_exit();
    audit_free(tsk);

    tsk->exit_code = code;
    taskstats_exit(tsk, group_dead);

    exit_mm(tsk);

    if (group_dead)
        acct_process();
    trace_sched_process_exit(tsk);

    exit_sem(tsk);
    exit_shm(tsk);
    exit_files(tsk);
    exit_fs(tsk);
    exit_task_work(tsk);
    check_stack_usage();
    exit_thread();

    /*
     * Flush inherited counters to the parent - before the parent
     * gets woken up by child-exit notifications.
     *
     * because of cgroup mode, must be called before cgroup_exit()
     */
    perf_event_exit_task(tsk);

    cgroup_exit(tsk, 1);

    if (group_dead)
        disassociate_ctty(1);

    module_put(task_thread_info(tsk)->exec_domain->module);

    proc_exit_connector(tsk);

    /*
     * FIXME: do that only when needed, using sched_exit tracepoint
     */
    ptrace_put_breakpoints(tsk);

    exit_notify(tsk, group_dead);
#ifdef CONFIG_NUMA
    task_lock(tsk);
    mpol_put(tsk->mempolicy);
    tsk->mempolicy = NULL;
    task_unlock(tsk);
#endif
#ifdef CONFIG_FUTEX
    if (unlikely(current->pi_state_cache))
        kfree(current->pi_state_cache);
#endif
    /*
     * Make sure we are holding no locks:
     */
    debug_check_no_locks_held(tsk);
    /*
     * We can do this unlocked here. The futex code uses this flag
     * just to verify whether the pi state cleanup has been done
     * or not. In the worst case it loops once more.
     */
    tsk->flags |= PF_EXITPIDONE;

    if (tsk->io_context)
        exit_io_context(tsk);

    if (tsk->splice_pipe)
        __free_pipe_info(tsk->splice_pipe);

    if (tsk->task_frag.page)
        put_page(tsk->task_frag.page);

    validate_creds_for_do_exit(tsk);

    preempt_disable();
    if (tsk->nr_dirtied)
        __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
    exit_rcu();

    /*
     * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
     * when the following two conditions become true.
     *   - There is race condition of mmap_sem (It is acquired by
     *     exit_mm()), and
     *   - SMI occurs before setting TASK_RUNINNG.
     *     (or hypervisor of virtual machine switches to other guest)
     *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
     *
     * To avoid it, we have to wait for releasing tsk->pi_lock which
     * is held by try_to_wake_up()
     */
    smp_mb();
    raw_spin_unlock_wait(&tsk->pi_lock);

    /* causes final put_task_struct in finish_task_switch(). */
    tsk->state = TASK_DEAD;
    tsk->flags |= PF_NOFREEZE;  /* tell freezer to ignore us */
    schedule();
    BUG();
    /* Avoid "noreturn function does return".  */
    for (;;)
        cpu_relax();    /* For when BUG is null */
}

EXPORT_SYMBOL_GPL(do_exit);

void complete_and_exit(struct completion *comp, long code)
{
    if (comp)
        complete(comp);

    do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

SYSCALL_DEFINE1(exit, int, error_code)
{
    do_exit((error_code&0xff)<<8);
}

/*
 * Take down every thread in the group.  This is called by fatal signals
 * as well as by sys_exit_group (below).
 */
void
do_group_exit(int exit_code)
{
    struct signal_struct *sig = current->signal;

    BUG_ON(exit_code & 0x80); /* core dumps don't get here */

    if (signal_group_exit(sig))
        exit_code = sig->group_exit_code;
    else if (!thread_group_empty(current)) {
        struct sighand_struct *const sighand = current->sighand;
        spin_lock_irq(&sighand->siglock);
        if (signal_group_exit(sig))
            /* Another thread got here before we took the lock.  */
            exit_code = sig->group_exit_code;
        else {
            sig->group_exit_code = exit_code;
            sig->flags = SIGNAL_GROUP_EXIT;
            zap_other_threads(current);
        }
        spin_unlock_irq(&sighand->siglock);
    }

    do_exit(exit_code);
    /* NOTREACHED */
}

/*
 * this kills every thread in the thread group. Note that any externally
 * wait4()-ing process will get the correct exit code - even if this
 * thread is not the thread group leader.
 */
SYSCALL_DEFINE1(exit_group, int, error_code)
{
    do_group_exit((error_code & 0xff) << 8);
    /* NOTREACHED */
    return 0;
}

struct wait_opts {
    enum pid_type       wo_type;
    int         wo_flags;
    struct pid      *wo_pid;

    struct siginfo __user   *wo_info;
    int __user      *wo_stat;
    struct rusage __user    *wo_rusage;

    wait_queue_t        child_wait;
    int         notask_error;
};

static inline
struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
{
    if (type != PIDTYPE_PID)
        task = task->group_leader;
    return task->pids[type].pid;
}

static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
{
    return  wo->wo_type == PIDTYPE_MAX ||
        task_pid_type(p, wo->wo_type) == wo->wo_pid;
}

static int eligible_child(struct wait_opts *wo, struct task_struct *p)
{
    if (!eligible_pid(wo, p))
        return 0;
    /* Wait for all children (clone and not) if __WALL is set;
     * otherwise, wait for clone children *only* if __WCLONE is
     * set; otherwise, wait for non-clone children *only*.  (Note:
     * A "clone" child here is one that reports to its parent
     * using a signal other than SIGCHLD.) */
    if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
        && !(wo->wo_flags & __WALL))
        return 0;

    return 1;
}

static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
                pid_t pid, uid_t uid, int why, int status)
{
    struct siginfo __user *infop;
    int retval = wo->wo_rusage
        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;

    put_task_struct(p);
    infop = wo->wo_info;
    if (infop) {
        if (!retval)
            retval = put_user(SIGCHLD, &infop->si_signo);
        if (!retval)
            retval = put_user(0, &infop->si_errno);
        if (!retval)
            retval = put_user((short)why, &infop->si_code);
        if (!retval)
            retval = put_user(pid, &infop->si_pid);
        if (!retval)
            retval = put_user(uid, &infop->si_uid);
        if (!retval)
            retval = put_user(status, &infop->si_status);
    }
    if (!retval)
        retval = pid;
    return retval;
}

/*
 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
 * the lock and this task is uninteresting.  If we return nonzero, we have
 * released the lock and the system call should return.
 */
static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
{
    unsigned long state;
    int retval, status, traced;
    pid_t pid = task_pid_vnr(p);
    uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
    struct siginfo __user *infop;

    if (!likely(wo->wo_flags & WEXITED))
        return 0;

    if (unlikely(wo->wo_flags & WNOWAIT)) {
        int exit_code = p->exit_code;
        int why;

        get_task_struct(p);
        read_unlock(&tasklist_lock);
        if ((exit_code & 0x7f) == 0) {
            why = CLD_EXITED;
            status = exit_code >> 8;
        } else {
            why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
            status = exit_code & 0x7f;
        }
        return wait_noreap_copyout(wo, p, pid, uid, why, status);
    }

    /*
     * Try to move the task's state to DEAD
     * only one thread is allowed to do this:
     */
    state = xchg(&p->exit_state, EXIT_DEAD);
    if (state != EXIT_ZOMBIE) {
        BUG_ON(state != EXIT_DEAD);
        return 0;
    }

    traced = ptrace_reparented(p);
    /*
     * It can be ptraced but not reparented, check
     * thread_group_leader() to filter out sub-threads.
     */
    if (likely(!traced) && thread_group_leader(p)) {
        struct signal_struct *psig;
        struct signal_struct *sig;
        unsigned long maxrss;
        cputime_t tgutime, tgstime;

        /*
         * The resource counters for the group leader are in its
         * own task_struct.  Those for dead threads in the group
         * are in its signal_struct, as are those for the child
         * processes it has previously reaped.  All these
         * accumulate in the parent's signal_struct c* fields.
         *
         * We don't bother to take a lock here to protect these
         * p->signal fields, because they are only touched by
         * __exit_signal, which runs with tasklist_lock
         * write-locked anyway, and so is excluded here.  We do
         * need to protect the access to parent->signal fields,
         * as other threads in the parent group can be right
         * here reaping other children at the same time.
         *
         * We use thread_group_times() to get times for the thread
         * group, which consolidates times for all threads in the
         * group including the group leader.
         */
        thread_group_times(p, &tgutime, &tgstime);
        spin_lock_irq(&p->real_parent->sighand->siglock);
        psig = p->real_parent->signal;
        sig = p->signal;
        psig->cutime += tgutime + sig->cutime;
        psig->cstime += tgstime + sig->cstime;
        psig->cgtime += p->gtime + sig->gtime + sig->cgtime;
        psig->cmin_flt +=
            p->min_flt + sig->min_flt + sig->cmin_flt;
        psig->cmaj_flt +=
            p->maj_flt + sig->maj_flt + sig->cmaj_flt;
        psig->cnvcsw +=
            p->nvcsw + sig->nvcsw + sig->cnvcsw;
        psig->cnivcsw +=
            p->nivcsw + sig->nivcsw + sig->cnivcsw;
        psig->cinblock +=
            task_io_get_inblock(p) +
            sig->inblock + sig->cinblock;
        psig->coublock +=
            task_io_get_oublock(p) +
            sig->oublock + sig->coublock;
        maxrss = max(sig->maxrss, sig->cmaxrss);
        if (psig->cmaxrss < maxrss)
            psig->cmaxrss = maxrss;
        task_io_accounting_add(&psig->ioac, &p->ioac);
        task_io_accounting_add(&psig->ioac, &sig->ioac);
        spin_unlock_irq(&p->real_parent->sighand->siglock);
    }

    /*
     * Now we are sure this task is interesting, and no other
     * thread can reap it because we set its state to EXIT_DEAD.
     */
    read_unlock(&tasklist_lock);

    retval = wo->wo_rusage
        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
    status = (p->signal->flags & SIGNAL_GROUP_EXIT)
        ? p->signal->group_exit_code : p->exit_code;
    if (!retval && wo->wo_stat)
        retval = put_user(status, wo->wo_stat);

    infop = wo->wo_info;
    if (!retval && infop)
        retval = put_user(SIGCHLD, &infop->si_signo);
    if (!retval && infop)
        retval = put_user(0, &infop->si_errno);
    if (!retval && infop) {
        int why;

        if ((status & 0x7f) == 0) {
            why = CLD_EXITED;
            status >>= 8;
        } else {
            why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
            status &= 0x7f;
        }
        retval = put_user((short)why, &infop->si_code);
        if (!retval)
            retval = put_user(status, &infop->si_status);
    }
    if (!retval && infop)
        retval = put_user(pid, &infop->si_pid);
    if (!retval && infop)
        retval = put_user(uid, &infop->si_uid);
    if (!retval)
        retval = pid;

    if (traced) {
        write_lock_irq(&tasklist_lock);
        /* We dropped tasklist, ptracer could die and untrace */
        ptrace_unlink(p);
        /*
         * If this is not a sub-thread, notify the parent.
         * If parent wants a zombie, don't release it now.
         */
        if (thread_group_leader(p) &&
            !do_notify_parent(p, p->exit_signal)) {
            p->exit_state = EXIT_ZOMBIE;
            p = NULL;
        }
        write_unlock_irq(&tasklist_lock);
    }
    if (p != NULL)
        release_task(p);

    return retval;
}

static int *task_stopped_code(struct task_struct *p, bool ptrace)
{
    if (ptrace) {
        if (task_is_stopped_or_traced(p) &&
            !(p->jobctl & JOBCTL_LISTENING))
            return &p->exit_code;
    } else {
        if (p->signal->flags & SIGNAL_STOP_STOPPED)
            return &p->signal->group_exit_code;
    }
    return NULL;
}

static int wait_task_stopped(struct wait_opts *wo,
                int ptrace, struct task_struct *p)
{
    struct siginfo __user *infop;
    int retval, exit_code, *p_code, why;
    uid_t uid = 0; /* unneeded, required by compiler */
    pid_t pid;

    /*
     * Traditionally we see ptrace'd stopped tasks regardless of options.
     */
    if (!ptrace && !(wo->wo_flags & WUNTRACED))
        return 0;

    if (!task_stopped_code(p, ptrace))
        return 0;

    exit_code = 0;
    spin_lock_irq(&p->sighand->siglock);

    p_code = task_stopped_code(p, ptrace);
    if (unlikely(!p_code))
        goto unlock_sig;

    exit_code = *p_code;
    if (!exit_code)
        goto unlock_sig;

    if (!unlikely(wo->wo_flags & WNOWAIT))
        *p_code = 0;

    uid = from_kuid_munged(current_user_ns(), task_uid(p));
unlock_sig:
    spin_unlock_irq(&p->sighand->siglock);
    if (!exit_code)
        return 0;

    /*
     * Now we are pretty sure this task is interesting.
     * Make sure it doesn't get reaped out from under us while we
     * give up the lock and then examine it below.  We don't want to
     * keep holding onto the tasklist_lock while we call getrusage and
     * possibly take page faults for user memory.
     */
    get_task_struct(p);
    pid = task_pid_vnr(p);
    why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
    read_unlock(&tasklist_lock);

    if (unlikely(wo->wo_flags & WNOWAIT))
        return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);

    retval = wo->wo_rusage
        ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
    if (!retval && wo->wo_stat)
        retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);

    infop = wo->wo_info;
    if (!retval && infop)
        retval = put_user(SIGCHLD, &infop->si_signo);
    if (!retval && infop)
        retval = put_user(0, &infop->si_errno);
    if (!retval && infop)
        retval = put_user((short)why, &infop->si_code);
    if (!retval && infop)
        retval = put_user(exit_code, &infop->si_status);
    if (!retval && infop)
        retval = put_user(pid, &infop->si_pid);
    if (!retval && infop)
        retval = put_user(uid, &infop->si_uid);
    if (!retval)
        retval = pid;
    put_task_struct(p);

    BUG_ON(!retval);
    return retval;
}

/*
 * Handle do_wait work for one task in a live, non-stopped state.
 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
 * the lock and this task is uninteresting.  If we return nonzero, we have
 * released the lock and the system call should return.
 */
static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
{
    int retval;
    pid_t pid;
    uid_t uid;

    if (!unlikely(wo->wo_flags & WCONTINUED))
        return 0;

    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
        return 0;

    spin_lock_irq(&p->sighand->siglock);
    /* Re-check with the lock held.  */
    if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
        spin_unlock_irq(&p->sighand->siglock);
        return 0;
    }
    if (!unlikely(wo->wo_flags & WNOWAIT))
        p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
    uid = from_kuid_munged(current_user_ns(), task_uid(p));
    spin_unlock_irq(&p->sighand->siglock);

    pid = task_pid_vnr(p);
    get_task_struct(p);
    read_unlock(&tasklist_lock);

    if (!wo->wo_info) {
        retval = wo->wo_rusage
            ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
        put_task_struct(p);
        if (!retval && wo->wo_stat)
            retval = put_user(0xffff, wo->wo_stat);
        if (!retval)
            retval = pid;
    } else {
        retval = wait_noreap_copyout(wo, p, pid, uid,
                         CLD_CONTINUED, SIGCONT);
        BUG_ON(retval == 0);
    }

    return retval;
}

/*
 * Consider @p for a wait by @parent.
 *
 * -ECHILD should be in ->notask_error before the first call.
 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
 * Returns zero if the search for a child should continue;
 * then ->notask_error is 0 if @p is an eligible child,
 * or another error from security_task_wait(), or still -ECHILD.
 */
static int wait_consider_task(struct wait_opts *wo, int ptrace,
                struct task_struct *p)
{
    int ret = eligible_child(wo, p);
    if (!ret)
        return ret;

    ret = security_task_wait(p);
    if (unlikely(ret < 0)) {
        /*
         * If we have not yet seen any eligible child,
         * then let this error code replace -ECHILD.
         * A permission error will give the user a clue
         * to look for security policy problems, rather
         * than for mysterious wait bugs.
         */
        if (wo->notask_error)
            wo->notask_error = ret;
        return 0;
    }

    /* dead body doesn't have much to contribute */
    if (unlikely(p->exit_state == EXIT_DEAD)) {
        /*
         * But do not ignore this task until the tracer does
         * wait_task_zombie()->do_notify_parent().
         */
        if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
            wo->notask_error = 0;
        return 0;
    }

    /* slay zombie? */
    if (p->exit_state == EXIT_ZOMBIE) {
        /*
         * A zombie ptracee is only visible to its ptracer.
         * Notification and reaping will be cascaded to the real
         * parent when the ptracer detaches.
         */
        if (likely(!ptrace) && unlikely(p->ptrace)) {
            /* it will become visible, clear notask_error */
            wo->notask_error = 0;
            return 0;
        }

        /* we don't reap group leaders with subthreads */
        if (!delay_group_leader(p))
            return wait_task_zombie(wo, p);

        /*
         * Allow access to stopped/continued state via zombie by
         * falling through.  Clearing of notask_error is complex.
         *
         * When !@ptrace:
         *
         * If WEXITED is set, notask_error should naturally be
         * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
         * so, if there are live subthreads, there are events to
         * wait for.  If all subthreads are dead, it's still safe
         * to clear - this function will be called again in finite
         * amount time once all the subthreads are released and
         * will then return without clearing.
         *
         * When @ptrace:
         *
         * Stopped state is per-task and thus can't change once the
         * target task dies.  Only continued and exited can happen.
         * Clear notask_error if WCONTINUED | WEXITED.
         */
        if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
            wo->notask_error = 0;
    } else {
        /*
         * If @p is ptraced by a task in its real parent's group,
         * hide group stop/continued state when looking at @p as
         * the real parent; otherwise, a single stop can be
         * reported twice as group and ptrace stops.
         *
         * If a ptracer wants to distinguish the two events for its
         * own children, it should create a separate process which
         * takes the role of real parent.
         */
        if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
            return 0;

        /*
         * @p is alive and it's gonna stop, continue or exit, so
         * there always is something to wait for.
         */
        wo->notask_error = 0;
    }

    /*
     * Wait for stopped.  Depending on @ptrace, different stopped state
     * is used and the two don't interact with each other.
     */
    ret = wait_task_stopped(wo, ptrace, p);
    if (ret)
        return ret;

    /*
     * Wait for continued.  There's only one continued state and the
     * ptracer can consume it which can confuse the real parent.  Don't
     * use WCONTINUED from ptracer.  You don't need or want it.
     */
    return wait_task_continued(wo, p);
}

/*
 * Do the work of do_wait() for one thread in the group, @tsk.
 *
 * -ECHILD should be in ->notask_error before the first call.
 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
 * Returns zero if the search for a child should continue; then
 * ->notask_error is 0 if there were any eligible children,
 * or another error from security_task_wait(), or still -ECHILD.
 */
static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
{
    struct task_struct *p;

    list_for_each_entry(p, &tsk->children, sibling) {
        int ret = wait_consider_task(wo, 0, p);
        if (ret)
            return ret;
    }

    return 0;
}

static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
{
    struct task_struct *p;

    list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
        int ret = wait_consider_task(wo, 1, p);
        if (ret)
            return ret;
    }

    return 0;
}

static int child_wait_callback(wait_queue_t *wait, unsigned mode,
                int sync, void *key)
{
    struct wait_opts *wo = container_of(wait, struct wait_opts,
                        child_wait);
    struct task_struct *p = key;

    if (!eligible_pid(wo, p))
        return 0;

    if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
        return 0;

    return default_wake_function(wait, mode, sync, key);
}

void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
{
    __wake_up_sync_key(&parent->signal->wait_chldexit,
                TASK_INTERRUPTIBLE, 1, p);
}

static long do_wait(struct wait_opts *wo)
{
    struct task_struct *tsk;
    int retval;

    trace_sched_process_wait(wo->wo_pid);

    init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
    wo->child_wait.private = current;
    add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
repeat:
    /*
     * If there is nothing that can match our critiera just get out.
     * We will clear ->notask_error to zero if we see any child that
     * might later match our criteria, even if we are not able to reap
     * it yet.
     */
    wo->notask_error = -ECHILD;
    if ((wo->wo_type < PIDTYPE_MAX) &&
       (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
        goto notask;

    set_current_state(TASK_INTERRUPTIBLE);
    read_lock(&tasklist_lock);
    tsk = current;
    do {
        retval = do_wait_thread(wo, tsk);
        if (retval)
            goto end;

        retval = ptrace_do_wait(wo, tsk);
        if (retval)
            goto end;

        if (wo->wo_flags & __WNOTHREAD)
            break;
    } while_each_thread(current, tsk);
    read_unlock(&tasklist_lock);

notask:
    retval = wo->notask_error;
    if (!retval && !(wo->wo_flags & WNOHANG)) {
        retval = -ERESTARTSYS;
        if (!signal_pending(current)) {
            schedule();
            goto repeat;
        }
    }
end:
    __set_current_state(TASK_RUNNING);
    remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
    return retval;
}

SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
        infop, int, options, struct rusage __user *, ru)
{
    struct wait_opts wo;
    struct pid *pid = NULL;
    enum pid_type type;
    long ret;

    if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
        return -EINVAL;
    if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
        return -EINVAL;

    switch (which) {
    case P_ALL:
        type = PIDTYPE_MAX;
        break;
    case P_PID:
        type = PIDTYPE_PID;
        if (upid <= 0)
            return -EINVAL;
        break;
    case P_PGID:
        type = PIDTYPE_PGID;
        if (upid <= 0)
            return -EINVAL;
        break;
    default:
        return -EINVAL;
    }

    if (type < PIDTYPE_MAX)
        pid = find_get_pid(upid);

    wo.wo_type  = type;
    wo.wo_pid   = pid;
    wo.wo_flags = options;
    wo.wo_info  = infop;
    wo.wo_stat  = NULL;
    wo.wo_rusage    = ru;
    ret = do_wait(&wo);

    if (ret > 0) {
        ret = 0;
    } else if (infop) {
        /*
         * For a WNOHANG return, clear out all the fields
         * we would set so the user can easily tell the
         * difference.
         */
        if (!ret)
            ret = put_user(0, &infop->si_signo);
        if (!ret)
            ret = put_user(0, &infop->si_errno);
        if (!ret)
            ret = put_user(0, &infop->si_code);
        if (!ret)
            ret = put_user(0, &infop->si_pid);
        if (!ret)
            ret = put_user(0, &infop->si_uid);
        if (!ret)
            ret = put_user(0, &infop->si_status);
    }

    put_pid(pid);

    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(5, ret, which, upid, infop, options, ru);
    return ret;
}

SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
        int, options, struct rusage __user *, ru)
{
    struct wait_opts wo;
    struct pid *pid = NULL;
    enum pid_type type;
    long ret;

    if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
            __WNOTHREAD|__WCLONE|__WALL))
        return -EINVAL;

    if (upid == -1)
        type = PIDTYPE_MAX;
    else if (upid < 0) {
        type = PIDTYPE_PGID;
        pid = find_get_pid(-upid);
    } else if (upid == 0) {
        type = PIDTYPE_PGID;
        pid = get_task_pid(current, PIDTYPE_PGID);
    } else /* upid > 0 */ {
        type = PIDTYPE_PID;
        pid = find_get_pid(upid);
    }

    wo.wo_type  = type;
    wo.wo_pid   = pid;
    wo.wo_flags = options | WEXITED;
    wo.wo_info  = NULL;
    wo.wo_stat  = stat_addr;
    wo.wo_rusage    = ru;
    ret = do_wait(&wo);
    put_pid(pid);

    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
    return ret;
}

#ifdef __ARCH_WANT_SYS_WAITPID

/*
 * sys_waitpid() remains for compatibility. waitpid() should be
 * implemented by calling sys_wait4() from libc.a.
 */
SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
{
    return sys_wait4(pid, stat_addr, options, NULL);
}

#endif