exit.c 42.2 KB
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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>
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#include <linux/capability.h>
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#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
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#include <linux/mnt_namespace.h>
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#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
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#include <linux/tsacct_kern.h>
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#include <linux/file.h>
#include <linux/binfmts.h>
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#include <linux/nsproxy.h>
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#include <linux/pid_namespace.h>
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#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
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#include <linux/kthread.h>
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#include <linux/mempolicy.h>
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#include <linux/taskstats_kern.h>
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#include <linux/delayacct.h>
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#include <linux/freezer.h>
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#include <linux/cgroup.h>
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#include <linux/syscalls.h>
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#include <linux/signal.h>
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#include <linux/posix-timers.h>
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#include <linux/cn_proc.h>
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#include <linux/mutex.h>
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#include <linux/futex.h>
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#include <linux/compat.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/audit.h> /* for audit_free() */
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#include <linux/resource.h>
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#include <linux/blkdev.h>
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#include <linux/task_io_accounting_ops.h>
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#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

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static void exit_mm(struct task_struct * tsk);

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static void __unhash_process(struct task_struct *p)
{
	nr_threads--;
	detach_pid(p, PIDTYPE_PID);
	if (thread_group_leader(p)) {
		detach_pid(p, PIDTYPE_PGID);
		detach_pid(p, PIDTYPE_SID);
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		list_del_rcu(&p->tasks);
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		__get_cpu_var(process_counts)--;
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	}
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	list_del_rcu(&p->thread_group);
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	remove_parent(p);
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}

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

	BUG_ON(!sig);
	BUG_ON(!atomic_read(&sig->count));

	rcu_read_lock();
	sighand = rcu_dereference(tsk->sighand);
	spin_lock(&sighand->siglock);

	posix_cpu_timers_exit(tsk);
	if (atomic_dec_and_test(&sig->count))
		posix_cpu_timers_exit_group(tsk);
	else {
		/*
		 * If there is any task waiting for the group exit
		 * then notify it:
		 */
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		if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
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			wake_up_process(sig->group_exit_task);
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		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 = cputime_add(sig->utime, tsk->utime);
		sig->stime = cputime_add(sig->stime, tsk->stime);
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		sig->gtime = cputime_add(sig->gtime, tsk->gtime);
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		sig->min_flt += tsk->min_flt;
		sig->maj_flt += tsk->maj_flt;
		sig->nvcsw += tsk->nvcsw;
		sig->nivcsw += tsk->nivcsw;
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		sig->inblock += task_io_get_inblock(tsk);
		sig->oublock += task_io_get_oublock(tsk);
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		sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
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		sig = NULL; /* Marker for below. */
	}

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	__unhash_process(tsk);

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	tsk->signal = NULL;
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	tsk->sighand = NULL;
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	spin_unlock(&sighand->siglock);
	rcu_read_unlock();

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	__cleanup_sighand(sighand);
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	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
	flush_sigqueue(&tsk->pending);
	if (sig) {
		flush_sigqueue(&sig->shared_pending);
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		taskstats_tgid_free(sig);
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		__cleanup_signal(sig);
	}
}

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static void delayed_put_task_struct(struct rcu_head *rhp)
{
	put_task_struct(container_of(rhp, struct task_struct, rcu));
}

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void release_task(struct task_struct * p)
{
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	struct task_struct *leader;
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	int zap_leader;
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repeat:
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	atomic_dec(&p->user->processes);
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	proc_flush_task(p);
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	write_lock_irq(&tasklist_lock);
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	ptrace_unlink(p);
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	BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
	__exit_signal(p);
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	/*
	 * 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) {
		BUG_ON(leader->exit_signal == -1);
		do_notify_parent(leader, leader->exit_signal);
		/*
		 * 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.
		 *
		 * do_notify_parent() will have marked it self-reaping in
		 * that case.
		 */
		zap_leader = (leader->exit_signal == -1);
	}

	write_unlock_irq(&tasklist_lock);
	release_thread(p);
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	call_rcu(&p->rcu, delayed_put_task_struct);
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	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...
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 *
 * The caller must hold rcu lock or the tasklist lock.
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 */
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struct pid *session_of_pgrp(struct pid *pgrp)
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{
	struct task_struct *p;
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	struct pid *sid = NULL;
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	p = pid_task(pgrp, PIDTYPE_PGID);
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	if (p == NULL)
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		p = pid_task(pgrp, PIDTYPE_PID);
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	if (p != NULL)
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		sid = task_session(p);
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	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?"
 */
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static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
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{
	struct task_struct *p;
	int ret = 1;

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	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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		if (p == ignored_task
				|| p->exit_state
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				|| is_global_init(p->real_parent))
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			continue;
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		if (task_pgrp(p->real_parent) != pgrp &&
		    task_session(p->real_parent) == task_session(p)) {
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			ret = 0;
			break;
		}
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	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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	return ret;	/* (sighing) "Often!" */
}

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int is_current_pgrp_orphaned(void)
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{
	int retval;

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

	return retval;
}

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static int has_stopped_jobs(struct pid *pgrp)
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{
	int retval = 0;
	struct task_struct *p;

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	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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		if (!task_is_stopped(p))
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			continue;
		retval = 1;
		break;
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	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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	return retval;
}

/**
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 * reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
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 *
 * If a kernel thread is launched as a result of a system call, or if
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 * it ever exits, it should generally reparent itself to kthreadd so it
 * isn't in the way of other processes and is correctly cleaned up on exit.
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 *
 * The various task state such as scheduling policy and priority may have
 * been inherited from a user process, so we reset them to sane values here.
 *
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 * NOTE that reparent_to_kthreadd() gives the caller full capabilities.
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 */
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static void reparent_to_kthreadd(void)
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{
	write_lock_irq(&tasklist_lock);

	ptrace_unlink(current);
	/* Reparent to init */
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	remove_parent(current);
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	current->real_parent = current->parent = kthreadd_task;
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	add_parent(current);
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	/* Set the exit signal to SIGCHLD so we signal init on exit */
	current->exit_signal = SIGCHLD;

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	if (task_nice(current) < 0)
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		set_user_nice(current, 0);
	/* cpus_allowed? */
	/* rt_priority? */
	/* signals? */
	security_task_reparent_to_init(current);
	memcpy(current->signal->rlim, init_task.signal->rlim,
	       sizeof(current->signal->rlim));
	atomic_inc(&(INIT_USER->__count));
	write_unlock_irq(&tasklist_lock);
	switch_uid(INIT_USER);
}

void __set_special_pids(pid_t session, pid_t pgrp)
{
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	struct task_struct *curr = current->group_leader;
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	if (task_session_nr(curr) != session) {
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		detach_pid(curr, PIDTYPE_SID);
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		set_task_session(curr, session);
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		attach_pid(curr, PIDTYPE_SID, find_pid(session));
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	}
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	if (task_pgrp_nr(curr) != pgrp) {
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		detach_pid(curr, PIDTYPE_PGID);
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		set_task_pgrp(curr, pgrp);
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		attach_pid(curr, PIDTYPE_PGID, find_pid(pgrp));
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	}
}

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static void set_special_pids(pid_t session, pid_t pgrp)
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{
	write_lock_irq(&tasklist_lock);
	__set_special_pids(session, pgrp);
	write_unlock_irq(&tasklist_lock);
}

/*
 * Let kernel threads use this to say that they
 * allow a certain signal (since daemonize() will
 * have disabled all of them by default).
 */
int allow_signal(int sig)
{
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	if (!valid_signal(sig) || sig < 1)
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		return -EINVAL;

	spin_lock_irq(&current->sighand->siglock);
	sigdelset(&current->blocked, sig);
	if (!current->mm) {
		/* 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)
{
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	if (!valid_signal(sig) || sig < 1)
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		return -EINVAL;

	spin_lock_irq(&current->sighand->siglock);
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	current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
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	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;
	struct fs_struct *fs;
	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);
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	/*
	 * We don't want to have TIF_FREEZE set if the system-wide hibernation
	 * or suspend transition begins right now.
	 */
	current->flags |= PF_NOFREEZE;
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	set_special_pids(1, 1);
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	proc_clear_tty(current);
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	/* Block and flush all signals */
	sigfillset(&blocked);
	sigprocmask(SIG_BLOCK, &blocked, NULL);
	flush_signals(current);

	/* Become as one with the init task */

	exit_fs(current);	/* current->fs->count--; */
	fs = init_task.fs;
	current->fs = fs;
	atomic_inc(&fs->count);
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	if (current->nsproxy != init_task.nsproxy) {
		get_nsproxy(init_task.nsproxy);
		switch_task_namespaces(current, init_task.nsproxy);
	}
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	exit_files(current);
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	current->files = init_task.files;
	atomic_inc(&current->files->count);

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	reparent_to_kthreadd();
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}

EXPORT_SYMBOL(daemonize);

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static void close_files(struct files_struct * files)
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{
	int i, j;
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	struct fdtable *fdt;
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	j = 0;
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	/*
	 * It is safe to dereference the fd table without RCU or
	 * ->file_lock because this is the last reference to the
	 * files structure.
	 */
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	fdt = files_fdtable(files);
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	for (;;) {
		unsigned long set;
		i = j * __NFDBITS;
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		if (i >= fdt->max_fds)
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			break;
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		set = fdt->open_fds->fds_bits[j++];
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		while (set) {
			if (set & 1) {
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				struct file * file = xchg(&fdt->fd[i], NULL);
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				if (file) {
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					filp_close(file, files);
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					cond_resched();
				}
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			}
			i++;
			set >>= 1;
		}
	}
}

struct files_struct *get_files_struct(struct task_struct *task)
{
	struct files_struct *files;

	task_lock(task);
	files = task->files;
	if (files)
		atomic_inc(&files->count);
	task_unlock(task);

	return files;
}

void fastcall put_files_struct(struct files_struct *files)
{
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	struct fdtable *fdt;

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	if (atomic_dec_and_test(&files->count)) {
		close_files(files);
		/*
		 * Free the fd and fdset arrays if we expanded them.
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		 * If the fdtable was embedded, pass files for freeing
		 * at the end of the RCU grace period. Otherwise,
		 * you can free files immediately.
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		 */
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		fdt = files_fdtable(files);
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		if (fdt != &files->fdtab)
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			kmem_cache_free(files_cachep, files);
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		free_fdtable(fdt);
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	}
}

EXPORT_SYMBOL(put_files_struct);

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void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
{
	struct files_struct *old;

	old = tsk->files;
	task_lock(tsk);
	tsk->files = files;
	task_unlock(tsk);
	put_files_struct(old);
}
EXPORT_SYMBOL(reset_files_struct);

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static void __exit_files(struct task_struct *tsk)
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{
	struct files_struct * files = tsk->files;

	if (files) {
		task_lock(tsk);
		tsk->files = NULL;
		task_unlock(tsk);
		put_files_struct(files);
	}
}

void exit_files(struct task_struct *tsk)
{
	__exit_files(tsk);
}

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static void __put_fs_struct(struct fs_struct *fs)
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{
	/* No need to hold fs->lock if we are killing it */
	if (atomic_dec_and_test(&fs->count)) {
		dput(fs->root);
		mntput(fs->rootmnt);
		dput(fs->pwd);
		mntput(fs->pwdmnt);
		if (fs->altroot) {
			dput(fs->altroot);
			mntput(fs->altrootmnt);
		}
		kmem_cache_free(fs_cachep, fs);
	}
}

void put_fs_struct(struct fs_struct *fs)
{
	__put_fs_struct(fs);
}

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static void __exit_fs(struct task_struct *tsk)
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{
	struct fs_struct * fs = tsk->fs;

	if (fs) {
		task_lock(tsk);
		tsk->fs = NULL;
		task_unlock(tsk);
		__put_fs_struct(fs);
	}
}

void exit_fs(struct task_struct *tsk)
{
	__exit_fs(tsk);
}

EXPORT_SYMBOL_GPL(exit_fs);

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

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

		wait_for_completion(&mm->core_done);
		down_read(&mm->mmap_sem);
	}
	atomic_inc(&mm->mm_count);
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	BUG_ON(mm != tsk->active_mm);
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	/* more a memory barrier than a real lock */
	task_lock(tsk);
	tsk->mm = NULL;
	up_read(&mm->mmap_sem);
	enter_lazy_tlb(mm, current);
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	/* We don't want this task to be frozen prematurely */
	clear_freeze_flag(tsk);
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	task_unlock(tsk);
	mmput(mm);
}

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static void
reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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{
596 597 598 599
	if (p->pdeath_signal)
		/* We already hold the tasklist_lock here.  */
		group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);

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	/* Move the child from its dying parent to the new one.  */
	if (unlikely(traced)) {
		/* Preserve ptrace links if someone else is tracing this child.  */
		list_del_init(&p->ptrace_list);
		if (p->parent != p->real_parent)
			list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
	} else {
		/* If this child is being traced, then we're the one tracing it
		 * anyway, so let go of it.
		 */
		p->ptrace = 0;
611
		remove_parent(p);
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		p->parent = p->real_parent;
613
		add_parent(p);
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		if (task_is_traced(p)) {
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			/*
			 * If it was at a trace stop, turn it into
			 * a normal stop since it's no longer being
			 * traced.
			 */
			ptrace_untrace(p);
		}
	}

625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641
	/* If this is a threaded reparent there is no need to
	 * notify anyone anything has happened.
	 */
	if (p->real_parent->group_leader == father->group_leader)
		return;

	/* We don't want people slaying init.  */
	if (p->exit_signal != -1)
		p->exit_signal = SIGCHLD;

	/* If we'd notified the old parent about this child's death,
	 * also notify the new parent.
	 */
	if (!traced && p->exit_state == EXIT_ZOMBIE &&
	    p->exit_signal != -1 && thread_group_empty(p))
		do_notify_parent(p, p->exit_signal);

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	/*
	 * process group orphan check
	 * Case ii: Our child is in a different pgrp
	 * than we are, and it was the only connection
	 * outside, so the child pgrp is now orphaned.
	 */
648 649 650
	if ((task_pgrp(p) != task_pgrp(father)) &&
	    (task_session(p) == task_session(father))) {
		struct pid *pgrp = task_pgrp(p);
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652 653
		if (will_become_orphaned_pgrp(pgrp, NULL) &&
		    has_stopped_jobs(pgrp)) {
654 655
			__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
			__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
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		}
	}
}

/*
 * When we die, we re-parent all our children.
 * Try to give them to another thread in our thread
 * group, and if no such member exists, give it to
664 665
 * the child reaper process (ie "init") in our pid
 * space.
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 */
667
static void forget_original_parent(struct task_struct *father)
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{
669
	struct task_struct *p, *n, *reaper = father;
670 671 672 673 674
	struct list_head ptrace_dead;

	INIT_LIST_HEAD(&ptrace_dead);

	write_lock_irq(&tasklist_lock);
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	do {
		reaper = next_thread(reaper);
		if (reaper == father) {
679
			reaper = task_child_reaper(father);
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			break;
		}
682
	} while (reaper->flags & PF_EXITING);
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	/*
	 * There are only two places where our children can be:
	 *
	 * - in our child list
	 * - in our ptraced child list
	 *
	 * Search them and reparent children.
	 */
692
	list_for_each_entry_safe(p, n, &father->children, sibling) {
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		int ptrace;

		ptrace = p->ptrace;

		/* if father isn't the real parent, then ptrace must be enabled */
		BUG_ON(father != p->real_parent && !ptrace);

		if (father == p->real_parent) {
			/* reparent with a reaper, real father it's us */
702
			p->real_parent = reaper;
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			reparent_thread(p, father, 0);
		} else {
			/* reparent ptraced task to its real parent */
			__ptrace_unlink (p);
			if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
			    thread_group_empty(p))
				do_notify_parent(p, p->exit_signal);
		}

		/*
		 * if the ptraced child is a zombie with exit_signal == -1
		 * we must collect it before we exit, or it will remain
		 * zombie forever since we prevented it from self-reap itself
		 * while it was being traced by us, to be able to see it in wait4.
		 */
		if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
719
			list_add(&p->ptrace_list, &ptrace_dead);
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	}
721

722
	list_for_each_entry_safe(p, n, &father->ptrace_children, ptrace_list) {
723
		p->real_parent = reaper;
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		reparent_thread(p, father, 1);
	}
726 727 728 729 730 731 732 733 734 735

	write_unlock_irq(&tasklist_lock);
	BUG_ON(!list_empty(&father->children));
	BUG_ON(!list_empty(&father->ptrace_children));

	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_list) {
		list_del_init(&p->ptrace_list);
		release_task(p);
	}

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}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
static void exit_notify(struct task_struct *tsk)
{
	int state;
	struct task_struct *t;
746
	struct pid *pgrp;
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	if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
	    && !thread_group_empty(tsk)) {
		/*
		 * This occurs when there was a race between our exit
		 * syscall and a group signal choosing us as the one to
		 * wake up.  It could be that we are the only thread
		 * alerted to check for pending signals, but another thread
		 * should be woken now to take the signal since we will not.
		 * Now we'll wake all the threads in the group just to make
		 * sure someone gets all the pending signals.
		 */
		spin_lock_irq(&tsk->sighand->siglock);
		for (t = next_thread(tsk); t != tsk; t = next_thread(t))
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Roland McGrath 已提交
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			if (!signal_pending(t) && !(t->flags & PF_EXITING))
				recalc_sigpending_and_wake(t);
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		spin_unlock_irq(&tsk->sighand->siglock);
	}

	/*
	 * 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)
	 */
774
	forget_original_parent(tsk);
775
	exit_task_namespaces(tsk);
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776

777
	write_lock_irq(&tasklist_lock);
L
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	/*
	 * 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)
	 *
	 * Case i: Our father is in a different pgrp than we are
	 * and we were the only connection outside, so our pgrp
	 * is about to become orphaned.
	 */
	t = tsk->real_parent;
788

789 790
	pgrp = task_pgrp(tsk);
	if ((task_pgrp(t) != pgrp) &&
791
	    (task_session(t) == task_session(tsk)) &&
792 793 794 795
	    will_become_orphaned_pgrp(pgrp, tsk) &&
	    has_stopped_jobs(pgrp)) {
		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
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796 797
	}

798
	/* Let father know we died
L
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799 800
	 *
	 * Thread signals are configurable, but you aren't going to use
801
	 * that to send signals to arbitary processes.
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	 * That stops right now.
	 *
	 * If the parent exec id doesn't match the exec id we saved
	 * when we started then we know the parent has changed security
	 * domain.
	 *
	 * If our self_exec id doesn't match our parent_exec_id then
	 * we have changed execution domain as these two values started
	 * the same after a fork.
	 */
	if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
	    ( tsk->parent_exec_id != t->self_exec_id  ||
	      tsk->self_exec_id != tsk->parent_exec_id)
	    && !capable(CAP_KILL))
		tsk->exit_signal = SIGCHLD;


	/* If something other than our normal parent is ptracing us, then
	 * send it a SIGCHLD instead of honoring exit_signal.  exit_signal
	 * only has special meaning to our real parent.
	 */
	if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
		int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
		do_notify_parent(tsk, signal);
	} else if (tsk->ptrace) {
		do_notify_parent(tsk, SIGCHLD);
	}

	state = EXIT_ZOMBIE;
831
	if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
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832 833 834
		state = EXIT_DEAD;
	tsk->exit_state = state;

835 836 837 838 839
	if (thread_group_leader(tsk) &&
	    tsk->signal->notify_count < 0 &&
	    tsk->signal->group_exit_task)
		wake_up_process(tsk->signal->group_exit_task);

L
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	write_unlock_irq(&tasklist_lock);

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

847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874
#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 *n = end_of_stack(current);
	unsigned long free;

	while (*n == 0)
		n++;
	free = (unsigned long)n - (unsigned long)end_of_stack(current);

	if (free >= lowest_to_date)
		return;

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

875 876
static inline void exit_child_reaper(struct task_struct *tsk)
{
877
	if (likely(tsk->group_leader != task_child_reaper(tsk)))
878 879
		return;

880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905
	if (tsk->nsproxy->pid_ns == &init_pid_ns)
		panic("Attempted to kill init!");

	/*
	 * @tsk is the last thread in the 'cgroup-init' and is exiting.
	 * Terminate all remaining processes in the namespace and reap them
	 * before exiting @tsk.
	 *
	 * Note that @tsk (last thread of cgroup-init) may not necessarily
	 * be the child-reaper (i.e main thread of cgroup-init) of the
	 * namespace i.e the child_reaper may have already exited.
	 *
	 * Even after a child_reaper exits, we let it inherit orphaned children,
	 * because, pid_ns->child_reaper remains valid as long as there is
	 * at least one living sub-thread in the cgroup init.

	 * This living sub-thread of the cgroup-init will be notified when
	 * a child inherited by the 'child-reaper' exits (do_notify_parent()
	 * uses __group_send_sig_info()). Further, when reaping child processes,
	 * do_wait() iterates over children of all living sub threads.

	 * i.e even though 'child_reaper' thread is listed as the parent of the
	 * orphaned children, any living sub-thread in the cgroup-init can
	 * perform the role of the child_reaper.
	 */
	zap_pid_ns_processes(tsk->nsproxy->pid_ns);
906 907
}

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

	profile_task_exit(tsk);

915 916
	WARN_ON(atomic_read(&tsk->fs_excl));

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917 918 919 920 921 922 923 924 925 926
	if (unlikely(in_interrupt()))
		panic("Aiee, killing interrupt handler!");
	if (unlikely(!tsk->pid))
		panic("Attempted to kill the idle task!");

	if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
		current->ptrace_message = code;
		ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
	}

927 928 929 930 931 932 933
	/*
	 * 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");
934 935 936 937 938 939 940 941 942 943
		/*
		 * 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;
944 945
		if (tsk->io_context)
			exit_io_context();
946 947 948 949
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule();
	}

950
	tsk->flags |= PF_EXITING;
951 952 953 954
	/*
	 * tsk->flags are checked in the futex code to protect against
	 * an exiting task cleaning up the robust pi futexes.
	 */
955 956
	smp_mb();
	spin_unlock_wait(&tsk->pi_lock);
L
Linus Torvalds 已提交
957 958 959

	if (unlikely(in_atomic()))
		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
960
				current->comm, task_pid_nr(current),
L
Linus Torvalds 已提交
961 962 963
				preempt_count());

	acct_update_integrals(tsk);
964 965 966 967
	if (tsk->mm) {
		update_hiwater_rss(tsk->mm);
		update_hiwater_vm(tsk->mm);
	}
L
Linus Torvalds 已提交
968
	group_dead = atomic_dec_and_test(&tsk->signal->live);
969
	if (group_dead) {
970
		exit_child_reaper(tsk);
971
		hrtimer_cancel(&tsk->signal->real_timer);
972
		exit_itimers(tsk->signal);
973
	}
974
	acct_collect(code, group_dead);
975
#ifdef CONFIG_FUTEX
976 977
	if (unlikely(tsk->robust_list))
		exit_robust_list(tsk);
978
#ifdef CONFIG_COMPAT
979 980
	if (unlikely(tsk->compat_robust_list))
		compat_exit_robust_list(tsk);
981
#endif
982
#endif
M
Miloslav Trmac 已提交
983 984
	if (group_dead)
		tty_audit_exit();
985 986
	if (unlikely(tsk->audit_context))
		audit_free(tsk);
987

988
	tsk->exit_code = code;
989
	taskstats_exit(tsk, group_dead);
990

L
Linus Torvalds 已提交
991 992
	exit_mm(tsk);

993
	if (group_dead)
994
		acct_process();
L
Linus Torvalds 已提交
995 996 997
	exit_sem(tsk);
	__exit_files(tsk);
	__exit_fs(tsk);
998
	check_stack_usage();
L
Linus Torvalds 已提交
999
	exit_thread();
1000
	cgroup_exit(tsk, 1);
L
Linus Torvalds 已提交
1001 1002 1003 1004 1005
	exit_keys(tsk);

	if (group_dead && tsk->signal->leader)
		disassociate_ctty(1);

A
Al Viro 已提交
1006
	module_put(task_thread_info(tsk)->exec_domain->module);
L
Linus Torvalds 已提交
1007 1008 1009
	if (tsk->binfmt)
		module_put(tsk->binfmt->module);

M
Matt Helsley 已提交
1010
	proc_exit_connector(tsk);
1011
	exit_notify(tsk);
L
Linus Torvalds 已提交
1012 1013 1014 1015
#ifdef CONFIG_NUMA
	mpol_free(tsk->mempolicy);
	tsk->mempolicy = NULL;
#endif
1016
#ifdef CONFIG_FUTEX
1017 1018 1019 1020 1021 1022 1023 1024
	/*
	 * This must happen late, after the PID is not
	 * hashed anymore:
	 */
	if (unlikely(!list_empty(&tsk->pi_state_list)))
		exit_pi_state_list(tsk);
	if (unlikely(current->pi_state_cache))
		kfree(current->pi_state_cache);
1025
#endif
1026
	/*
1027
	 * Make sure we are holding no locks:
1028
	 */
1029
	debug_check_no_locks_held(tsk);
1030 1031 1032 1033 1034 1035
	/*
	 * 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;
L
Linus Torvalds 已提交
1036

1037 1038 1039
	if (tsk->io_context)
		exit_io_context();

1040 1041 1042
	if (tsk->splice_pipe)
		__free_pipe_info(tsk->splice_pipe);

C
Coywolf Qi Hunt 已提交
1043
	preempt_disable();
O
Oleg Nesterov 已提交
1044
	/* causes final put_task_struct in finish_task_switch(). */
1045
	tsk->state = TASK_DEAD;
C
Coywolf Qi Hunt 已提交
1046

L
Linus Torvalds 已提交
1047 1048 1049
	schedule();
	BUG();
	/* Avoid "noreturn function does return".  */
A
Alan Cox 已提交
1050 1051
	for (;;)
		cpu_relax();	/* For when BUG is null */
L
Linus Torvalds 已提交
1052 1053
}

1054 1055
EXPORT_SYMBOL_GPL(do_exit);

L
Linus Torvalds 已提交
1056 1057 1058 1059
NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
	if (comp)
		complete(comp);
O
Oleg Nesterov 已提交
1060

L
Linus Torvalds 已提交
1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085
	do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

asmlinkage long sys_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).
 */
NORET_TYPE void
do_group_exit(int exit_code)
{
	BUG_ON(exit_code & 0x80); /* core dumps don't get here */

	if (current->signal->flags & SIGNAL_GROUP_EXIT)
		exit_code = current->signal->group_exit_code;
	else if (!thread_group_empty(current)) {
		struct signal_struct *const sig = current->signal;
		struct sighand_struct *const sighand = current->sighand;
		spin_lock_irq(&sighand->siglock);
1086
		if (signal_group_exit(sig))
L
Linus Torvalds 已提交
1087 1088 1089 1090
			/* Another thread got here before we took the lock.  */
			exit_code = sig->group_exit_code;
		else {
			sig->group_exit_code = exit_code;
1091
			sig->flags = SIGNAL_GROUP_EXIT;
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1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110
			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.
 */
asmlinkage void sys_exit_group(int error_code)
{
	do_group_exit((error_code & 0xff) << 8);
}

1111
static int eligible_child(pid_t pid, int options, struct task_struct *p)
L
Linus Torvalds 已提交
1112
{
1113
	int err;
1114
	struct pid_namespace *ns;
1115

1116
	ns = current->nsproxy->pid_ns;
L
Linus Torvalds 已提交
1117
	if (pid > 0) {
1118
		if (task_pid_nr_ns(p, ns) != pid)
L
Linus Torvalds 已提交
1119 1120
			return 0;
	} else if (!pid) {
1121
		if (task_pgrp_nr_ns(p, ns) != task_pgrp_vnr(current))
L
Linus Torvalds 已提交
1122 1123
			return 0;
	} else if (pid != -1) {
1124
		if (task_pgrp_nr_ns(p, ns) != -pid)
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			return 0;
	}

	/*
	 * Do not consider detached threads that are
	 * not ptraced:
	 */
	if (p->exit_signal == -1 && !p->ptrace)
		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) ^ ((options & __WCLONE) != 0))
	    && !(options & __WALL))
		return 0;
	/*
	 * Do not consider thread group leaders that are
	 * in a non-empty thread group:
	 */
1147
	if (delay_group_leader(p))
L
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1148 1149
		return 2;

1150 1151 1152
	err = security_task_wait(p);
	if (err)
		return err;
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	return 1;
}

1157
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
L
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1158 1159 1160 1161 1162
			       int why, int status,
			       struct siginfo __user *infop,
			       struct rusage __user *rusagep)
{
	int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1163

L
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1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187
	put_task_struct(p);
	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.
 */
1188
static int wait_task_zombie(struct task_struct *p, int noreap,
L
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			    struct siginfo __user *infop,
			    int __user *stat_addr, struct rusage __user *ru)
{
	unsigned long state;
1193
	int retval, status, traced;
1194 1195 1196
	struct pid_namespace *ns;

	ns = current->nsproxy->pid_ns;
L
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1197 1198

	if (unlikely(noreap)) {
1199
		pid_t pid = task_pid_nr_ns(p, ns);
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1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230
		uid_t uid = p->uid;
		int exit_code = p->exit_code;
		int why, status;

		if (unlikely(p->exit_state != EXIT_ZOMBIE))
			return 0;
		if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
			return 0;
		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(p, pid, uid, why,
					   status, infop, ru);
	}

	/*
	 * 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;
	}

1231 1232 1233 1234
	/* traced means p->ptrace, but not vice versa */
	traced = (p->real_parent != p->parent);

	if (likely(!traced)) {
1235 1236 1237
		struct signal_struct *psig;
		struct signal_struct *sig;

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Linus Torvalds 已提交
1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253
		/*
		 * 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 p->parent->signal fields,
		 * as other threads in the parent group can be right
		 * here reaping other children at the same time.
		 */
		spin_lock_irq(&p->parent->sighand->siglock);
1254 1255 1256 1257
		psig = p->parent->signal;
		sig = p->signal;
		psig->cutime =
			cputime_add(psig->cutime,
L
Linus Torvalds 已提交
1258
			cputime_add(p->utime,
1259 1260 1261 1262
			cputime_add(sig->utime,
				    sig->cutime)));
		psig->cstime =
			cputime_add(psig->cstime,
L
Linus Torvalds 已提交
1263
			cputime_add(p->stime,
1264 1265
			cputime_add(sig->stime,
				    sig->cstime)));
1266 1267 1268 1269 1270
		psig->cgtime =
			cputime_add(psig->cgtime,
			cputime_add(p->gtime,
			cputime_add(sig->gtime,
				    sig->cgtime)));
1271 1272 1273 1274 1275 1276 1277 1278
		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;
1279 1280 1281 1282 1283 1284
		psig->cinblock +=
			task_io_get_inblock(p) +
			sig->inblock + sig->cinblock;
		psig->coublock +=
			task_io_get_oublock(p) +
			sig->oublock + sig->coublock;
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1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317
		spin_unlock_irq(&p->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 = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
		? p->signal->group_exit_code : p->exit_code;
	if (!retval && stat_addr)
		retval = put_user(status, stat_addr);
	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)
1318
		retval = put_user(task_pid_nr_ns(p, ns), &infop->si_pid);
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Linus Torvalds 已提交
1319 1320
	if (!retval && infop)
		retval = put_user(p->uid, &infop->si_uid);
1321
	if (!retval)
1322
		retval = task_pid_nr_ns(p, ns);
1323 1324

	if (traced) {
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1325
		write_lock_irq(&tasklist_lock);
1326 1327 1328 1329 1330 1331 1332 1333 1334
		/* We dropped tasklist, ptracer could die and untrace */
		ptrace_unlink(p);
		/*
		 * If this is not a detached task, notify the parent.
		 * If it's still not detached after that, don't release
		 * it now.
		 */
		if (p->exit_signal != -1) {
			do_notify_parent(p, p->exit_signal);
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			if (p->exit_signal != -1) {
1336 1337
				p->exit_state = EXIT_ZOMBIE;
				p = NULL;
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1338 1339 1340 1341 1342 1343
			}
		}
		write_unlock_irq(&tasklist_lock);
	}
	if (p != NULL)
		release_task(p);
1344

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1345 1346 1347 1348 1349 1350 1351 1352 1353
	return retval;
}

/*
 * Handle sys_wait4 work for one task in state TASK_STOPPED.  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.
 */
1354
static int wait_task_stopped(struct task_struct *p,
1355
			     int noreap, struct siginfo __user *infop,
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1356 1357
			     int __user *stat_addr, struct rusage __user *ru)
{
1358 1359
	int retval, exit_code, why;
	uid_t uid = 0; /* unneeded, required by compiler */
1360
	pid_t pid;
L
Linus Torvalds 已提交
1361

1362 1363 1364 1365 1366 1367
	exit_code = 0;
	spin_lock_irq(&p->sighand->siglock);

	if (unlikely(!task_is_stopped_or_traced(p)))
		goto unlock_sig;

1368
	if (!(p->ptrace & PT_PTRACED) && p->signal->group_stop_count > 0)
L
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1369 1370 1371 1372
		/*
		 * A group stop is in progress and this is the group leader.
		 * We won't report until all threads have stopped.
		 */
1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385
		goto unlock_sig;

	exit_code = p->exit_code;
	if (!exit_code)
		goto unlock_sig;

	if (!noreap)
		p->exit_code = 0;

	uid = p->uid;
unlock_sig:
	spin_unlock_irq(&p->sighand->siglock);
	if (!exit_code)
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Linus Torvalds 已提交
1386 1387 1388 1389 1390 1391 1392 1393 1394 1395
		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);
1396 1397
	pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);
	why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
L
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1398 1399
	read_unlock(&tasklist_lock);

1400
	if (unlikely(noreap))
L
Linus Torvalds 已提交
1401
		return wait_noreap_copyout(p, pid, uid,
1402
					   why, exit_code,
L
Linus Torvalds 已提交
1403 1404 1405 1406 1407 1408 1409 1410 1411 1412
					   infop, ru);

	retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
	if (!retval && stat_addr)
		retval = put_user((exit_code << 8) | 0x7f, stat_addr);
	if (!retval && infop)
		retval = put_user(SIGCHLD, &infop->si_signo);
	if (!retval && infop)
		retval = put_user(0, &infop->si_errno);
	if (!retval && infop)
1413
		retval = put_user(why, &infop->si_code);
L
Linus Torvalds 已提交
1414 1415 1416
	if (!retval && infop)
		retval = put_user(exit_code, &infop->si_status);
	if (!retval && infop)
1417
		retval = put_user(pid, &infop->si_pid);
L
Linus Torvalds 已提交
1418
	if (!retval && infop)
1419
		retval = put_user(uid, &infop->si_uid);
L
Linus Torvalds 已提交
1420
	if (!retval)
1421
		retval = pid;
L
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1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433
	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.
 */
1434
static int wait_task_continued(struct task_struct *p, int noreap,
L
Linus Torvalds 已提交
1435 1436 1437 1438 1439 1440
			       struct siginfo __user *infop,
			       int __user *stat_addr, struct rusage __user *ru)
{
	int retval;
	pid_t pid;
	uid_t uid;
1441
	struct pid_namespace *ns;
L
Linus Torvalds 已提交
1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455

	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 (!noreap)
		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
	spin_unlock_irq(&p->sighand->siglock);

1456 1457
	ns = current->nsproxy->pid_ns;
	pid = task_pid_nr_ns(p, ns);
L
Linus Torvalds 已提交
1458 1459 1460 1461 1462 1463 1464 1465 1466 1467
	uid = p->uid;
	get_task_struct(p);
	read_unlock(&tasklist_lock);

	if (!infop) {
		retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
		put_task_struct(p);
		if (!retval && stat_addr)
			retval = put_user(0xffff, stat_addr);
		if (!retval)
1468
			retval = task_pid_nr_ns(p, ns);
L
Linus Torvalds 已提交
1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484
	} else {
		retval = wait_noreap_copyout(p, pid, uid,
					     CLD_CONTINUED, SIGCONT,
					     infop, ru);
		BUG_ON(retval == 0);
	}

	return retval;
}

static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
		    int __user *stat_addr, struct rusage __user *ru)
{
	DECLARE_WAITQUEUE(wait, current);
	struct task_struct *tsk;
	int flag, retval;
1485
	int allowed, denied;
L
Linus Torvalds 已提交
1486 1487 1488 1489 1490 1491 1492 1493

	add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
	/*
	 * We will set this flag if we see any child that might later
	 * match our criteria, even if we are not able to reap it yet.
	 */
	flag = 0;
1494
	allowed = denied = 0;
L
Linus Torvalds 已提交
1495 1496 1497 1498 1499 1500 1501
	current->state = TASK_INTERRUPTIBLE;
	read_lock(&tasklist_lock);
	tsk = current;
	do {
		struct task_struct *p;
		int ret;

1502
		list_for_each_entry(p, &tsk->children, sibling) {
L
Linus Torvalds 已提交
1503 1504 1505 1506
			ret = eligible_child(pid, options, p);
			if (!ret)
				continue;

1507 1508 1509 1510 1511 1512
			if (unlikely(ret < 0)) {
				denied = ret;
				continue;
			}
			allowed = 1;

1513
			retval = 0;
M
Matthew Wilcox 已提交
1514
			if (task_is_stopped_or_traced(p)) {
L
Linus Torvalds 已提交
1515 1516 1517 1518 1519
				/*
				 * It's stopped now, so it might later
				 * continue, exit, or stop again.
				 */
				flag = 1;
O
Oleg Nesterov 已提交
1520 1521 1522
				if (!(p->ptrace & PT_PTRACED) &&
				    !(options & WUNTRACED))
					continue;
M
Matthew Wilcox 已提交
1523

1524
				retval = wait_task_stopped(p,
M
Matthew Wilcox 已提交
1525 1526 1527 1528 1529 1530 1531 1532 1533
						(options & WNOWAIT), infop,
						stat_addr, ru);
			} else if (p->exit_state == EXIT_ZOMBIE) {
				/*
				 * Eligible but we cannot release it yet:
				 */
				if (ret == 2)
					goto check_continued;
				if (!likely(options & WEXITED))
L
Linus Torvalds 已提交
1534
					continue;
M
Matthew Wilcox 已提交
1535 1536 1537
				retval = wait_task_zombie(p,
						(options & WNOWAIT), infop,
						stat_addr, ru);
1538
			} else if (p->exit_state != EXIT_DEAD) {
L
Linus Torvalds 已提交
1539 1540 1541 1542 1543 1544 1545 1546
check_continued:
				/*
				 * It's running now, so it might later
				 * exit, stop, or stop and then continue.
				 */
				flag = 1;
				if (!unlikely(options & WCONTINUED))
					continue;
M
Matthew Wilcox 已提交
1547 1548 1549
				retval = wait_task_continued(p,
						(options & WNOWAIT), infop,
						stat_addr, ru);
L
Linus Torvalds 已提交
1550
			}
1551 1552
			if (retval != 0) /* tasklist_lock released */
				goto end;
L
Linus Torvalds 已提交
1553 1554
		}
		if (!flag) {
1555 1556
			list_for_each_entry(p, &tsk->ptrace_children,
					    ptrace_list) {
L
Linus Torvalds 已提交
1557 1558 1559 1560 1561 1562 1563 1564 1565
				if (!eligible_child(pid, options, p))
					continue;
				flag = 1;
				break;
			}
		}
		if (options & __WNOTHREAD)
			break;
		tsk = next_thread(tsk);
E
Eric Sesterhenn 已提交
1566
		BUG_ON(tsk->signal != current->signal);
L
Linus Torvalds 已提交
1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580
	} while (tsk != current);

	read_unlock(&tasklist_lock);
	if (flag) {
		retval = 0;
		if (options & WNOHANG)
			goto end;
		retval = -ERESTARTSYS;
		if (signal_pending(current))
			goto end;
		schedule();
		goto repeat;
	}
	retval = -ECHILD;
1581 1582
	if (unlikely(denied) && !allowed)
		retval = denied;
L
Linus Torvalds 已提交
1583 1584 1585 1586 1587
end:
	current->state = TASK_RUNNING;
	remove_wait_queue(&current->signal->wait_chldexit,&wait);
	if (infop) {
		if (retval > 0)
1588
			retval = 0;
L
Linus Torvalds 已提交
1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673
		else {
			/*
			 * For a WNOHANG return, clear out all the fields
			 * we would set so the user can easily tell the
			 * difference.
			 */
			if (!retval)
				retval = put_user(0, &infop->si_signo);
			if (!retval)
				retval = put_user(0, &infop->si_errno);
			if (!retval)
				retval = put_user(0, &infop->si_code);
			if (!retval)
				retval = put_user(0, &infop->si_pid);
			if (!retval)
				retval = put_user(0, &infop->si_uid);
			if (!retval)
				retval = put_user(0, &infop->si_status);
		}
	}
	return retval;
}

asmlinkage long sys_waitid(int which, pid_t pid,
			   struct siginfo __user *infop, int options,
			   struct rusage __user *ru)
{
	long ret;

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

	switch (which) {
	case P_ALL:
		pid = -1;
		break;
	case P_PID:
		if (pid <= 0)
			return -EINVAL;
		break;
	case P_PGID:
		if (pid <= 0)
			return -EINVAL;
		pid = -pid;
		break;
	default:
		return -EINVAL;
	}

	ret = do_wait(pid, options, infop, NULL, ru);

	/* avoid REGPARM breakage on x86: */
	prevent_tail_call(ret);
	return ret;
}

asmlinkage long sys_wait4(pid_t pid, int __user *stat_addr,
			  int options, struct rusage __user *ru)
{
	long ret;

	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
			__WNOTHREAD|__WCLONE|__WALL))
		return -EINVAL;
	ret = do_wait(pid, options | WEXITED, NULL, stat_addr, ru);

	/* avoid REGPARM breakage on x86: */
	prevent_tail_call(ret);
	return ret;
}

#ifdef __ARCH_WANT_SYS_WAITPID

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

#endif