exit.c 45.2 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/iocontext.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>
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#include <linux/fdtable.h>
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#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/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 <linux/tracehook.h>
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#include <linux/init_task.h>
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#include <trace/sched.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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#include "cred-internals.h"
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DEFINE_TRACE(sched_process_free);
DEFINE_TRACE(sched_process_exit);
DEFINE_TRACE(sched_process_wait);
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static void exit_mm(struct task_struct * tsk);

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static inline int task_detached(struct task_struct *p)
{
	return p->exit_signal == -1;
}

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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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	list_del_init(&p->sibling);
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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));

	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.
		 */
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		sig->utime = cputime_add(sig->utime, task_utime(tsk));
		sig->stime = cputime_add(sig->stime, task_stime(tsk));
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		sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
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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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		task_io_accounting_add(&sig->ioac, &tsk->ioac);
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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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	/*
	 * Do this under ->siglock, we can race with another thread
	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
	 */
	flush_sigqueue(&tsk->pending);

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

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	__cleanup_sighand(sighand);
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	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
	if (sig) {
		flush_sigqueue(&sig->shared_pending);
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		taskstats_tgid_free(sig);
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		/*
		 * Make sure ->signal can't go away under rq->lock,
		 * see account_group_exec_runtime().
		 */
		task_rq_unlock_wait(tsk);
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		__cleanup_signal(sig);
	}
}

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

	trace_sched_process_free(tsk);
	put_task_struct(tsk);
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}

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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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	tracehook_prepare_release_task(p);
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	/* don't need to get the RCU readlock here - the process is dead and
	 * can't be modifying its own credentials */
	atomic_dec(&__task_cred(p)->user->processes);

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	proc_flush_task(p);
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	write_lock_irq(&tasklist_lock);
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	tracehook_finish_release_task(p);
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	__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) {
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		BUG_ON(task_detached(leader));
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		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.
		 */
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		zap_leader = task_detached(leader);
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		/*
		 * This maintains the invariant that release_task()
		 * only runs on a task in EXIT_DEAD, just for sanity.
		 */
		if (zap_leader)
			leader->exit_state = EXIT_DEAD;
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	}

	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;

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	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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		if ((p == ignored_task) ||
		    (p->exit_state && thread_group_empty(p)) ||
		    is_global_init(p->real_parent))
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			continue;
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		if (task_pgrp(p->real_parent) != pgrp &&
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		    task_session(p->real_parent) == task_session(p))
			return 0;
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	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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	return 1;
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}

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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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/*
 * 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);
	}
}

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/**
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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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	current->real_parent = current->parent = kthreadd_task;
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	list_move_tail(&current->sibling, &current->real_parent->children);
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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? */
	memcpy(current->signal->rlim, init_task.signal->rlim,
	       sizeof(current->signal->rlim));
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	atomic_inc(&init_cred.usage);
	commit_creds(&init_cred);
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	write_unlock_irq(&tasklist_lock);
}

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void __set_special_pids(struct pid *pid)
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{
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	struct task_struct *curr = current->group_leader;
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	pid_t nr = pid_nr(pid);
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	if (task_session(curr) != pid) {
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		change_pid(curr, PIDTYPE_SID, pid);
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		set_task_session(curr, nr);
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	}
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	if (task_pgrp(curr) != pid) {
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		change_pid(curr, PIDTYPE_PGID, pid);
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		set_task_pgrp(curr, nr);
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	}
}

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static void set_special_pids(struct pid *pid)
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{
	write_lock_irq(&tasklist_lock);
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	__set_special_pids(pid);
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	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;
	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.
	 */
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	current->flags |= (PF_NOFREEZE | PF_KTHREAD);
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	if (current->nsproxy != &init_nsproxy) {
		get_nsproxy(&init_nsproxy);
		switch_task_namespaces(current, &init_nsproxy);
	}
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	set_special_pids(&init_struct_pid);
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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 */

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	daemonize_fs_struct();
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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;
}

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void put_files_struct(struct files_struct *files)
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{
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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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	}
}

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

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

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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);
	}
}

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#ifdef CONFIG_MM_OWNER
/*
 * Task p is exiting and it owned mm, lets find a new owner for it
 */
static inline int
mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
{
	/*
	 * If there are other users of the mm and the owner (us) is exiting
	 * we need to find a new owner to take on the responsibility.
	 */
	if (atomic_read(&mm->mm_users) <= 1)
		return 0;
	if (mm->owner != p)
		return 0;
	return 1;
}

void mm_update_next_owner(struct mm_struct *mm)
{
	struct task_struct *c, *g, *p = current;

retry:
	if (!mm_need_new_owner(mm, p))
		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->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);
616 617 618
	/*
	 * We found no owner yet mm_users > 1: this implies that we are
	 * most likely racing with swapoff (try_to_unuse()) or /proc or
619
	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
620 621
	 */
	mm->owner = NULL;
622 623 624 625 626 627 628 629 630 631
	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);
632 633 634 635 636
	/*
	 * Delay read_unlock() till we have the task_lock()
	 * to ensure that c does not slip away underneath us
	 */
	read_unlock(&tasklist_lock);
637 638 639 640 641 642 643 644 645 646 647
	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 */

L
Linus Torvalds 已提交
648 649 650 651
/*
 * Turn us into a lazy TLB process if we
 * aren't already..
 */
A
Adrian Bunk 已提交
652
static void exit_mm(struct task_struct * tsk)
L
Linus Torvalds 已提交
653 654
{
	struct mm_struct *mm = tsk->mm;
655
	struct core_state *core_state;
L
Linus Torvalds 已提交
656 657 658 659 660 661

	mm_release(tsk, mm);
	if (!mm)
		return;
	/*
	 * Serialize with any possible pending coredump.
662
	 * We must hold mmap_sem around checking core_state
L
Linus Torvalds 已提交
663
	 * and clearing tsk->mm.  The core-inducing thread
664
	 * will increment ->nr_threads for each thread in the
L
Linus Torvalds 已提交
665 666 667
	 * group with ->mm != NULL.
	 */
	down_read(&mm->mmap_sem);
668 669 670
	core_state = mm->core_state;
	if (core_state) {
		struct core_thread self;
L
Linus Torvalds 已提交
671 672
		up_read(&mm->mmap_sem);

673 674 675 676 677 678 679 680
		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);
L
Linus Torvalds 已提交
681

O
Oleg Nesterov 已提交
682 683 684 685 686 687 688
		for (;;) {
			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
			if (!self.task) /* see coredump_finish() */
				break;
			schedule();
		}
		__set_task_state(tsk, TASK_RUNNING);
L
Linus Torvalds 已提交
689 690 691
		down_read(&mm->mmap_sem);
	}
	atomic_inc(&mm->mm_count);
E
Eric Sesterhenn 已提交
692
	BUG_ON(mm != tsk->active_mm);
L
Linus Torvalds 已提交
693 694 695 696 697
	/* more a memory barrier than a real lock */
	task_lock(tsk);
	tsk->mm = NULL;
	up_read(&mm->mmap_sem);
	enter_lazy_tlb(mm, current);
698 699
	/* We don't want this task to be frozen prematurely */
	clear_freeze_flag(tsk);
L
Linus Torvalds 已提交
700
	task_unlock(tsk);
701
	mm_update_next_owner(mm);
L
Linus Torvalds 已提交
702 703 704
	mmput(mm);
}

705 706 707 708 709 710
/*
 * Return nonzero if @parent's children should reap themselves.
 *
 * Called with write_lock_irq(&tasklist_lock) held.
 */
static int ignoring_children(struct task_struct *parent)
L
Linus Torvalds 已提交
711
{
712 713 714 715 716 717 718 719 720
	int ret;
	struct sighand_struct *psig = parent->sighand;
	unsigned long flags;
	spin_lock_irqsave(&psig->siglock, flags);
	ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
	       (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
	spin_unlock_irqrestore(&psig->siglock, flags);
	return ret;
}
721

R
Roland McGrath 已提交
722 723 724 725 726 727 728
/*
 * Detach all tasks we were using ptrace on.
 * Any that need to be release_task'd are put on the @dead list.
 *
 * Called with write_lock(&tasklist_lock) held.
 */
static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
L
Linus Torvalds 已提交
729
{
R
Roland McGrath 已提交
730
	struct task_struct *p, *n;
731
	int ign = -1;
732

R
Roland McGrath 已提交
733 734 735 736 737 738 739 740 741 742 743 744 745 746
	list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
		__ptrace_unlink(p);

		if (p->exit_state != EXIT_ZOMBIE)
			continue;

		/*
		 * If it's a zombie, our attachedness prevented normal
		 * parent notification or self-reaping.  Do notification
		 * now if it would have happened earlier.  If it should
		 * reap itself, add it to the @dead list.  We can't call
		 * release_task() here because we already hold tasklist_lock.
		 *
		 * If it's our own child, there is no notification to do.
747 748
		 * But if our normal children self-reap, then this child
		 * was prevented by ptrace and we must reap it now.
L
Linus Torvalds 已提交
749
		 */
R
Roland McGrath 已提交
750 751 752
		if (!task_detached(p) && thread_group_empty(p)) {
			if (!same_thread_group(p->real_parent, parent))
				do_notify_parent(p, p->exit_signal);
753 754 755 756 757 758
			else {
				if (ign < 0)
					ign = ignoring_children(parent);
				if (ign)
					p->exit_signal = -1;
			}
R
Roland McGrath 已提交
759
		}
L
Linus Torvalds 已提交
760

R
Roland McGrath 已提交
761
		if (task_detached(p)) {
L
Linus Torvalds 已提交
762
			/*
R
Roland McGrath 已提交
763
			 * Mark it as in the process of being reaped.
L
Linus Torvalds 已提交
764
			 */
R
Roland McGrath 已提交
765 766
			p->exit_state = EXIT_DEAD;
			list_add(&p->ptrace_entry, dead);
L
Linus Torvalds 已提交
767 768
		}
	}
R
Roland McGrath 已提交
769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
}

/*
 * Finish up exit-time ptrace cleanup.
 *
 * Called without locks.
 */
static void ptrace_exit_finish(struct task_struct *parent,
			       struct list_head *dead)
{
	struct task_struct *p, *n;

	BUG_ON(!list_empty(&parent->ptraced));

	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
		list_del_init(&p->ptrace_entry);
		release_task(p);
	}
}

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

	list_move_tail(&p->sibling, &p->real_parent->children);
L
Linus Torvalds 已提交
796

797 798 799
	/* If this is a threaded reparent there is no need to
	 * notify anyone anything has happened.
	 */
800
	if (same_thread_group(p->real_parent, father))
801 802 803
		return;

	/* We don't want people slaying init.  */
804
	if (!task_detached(p))
805 806 807 808 809
		p->exit_signal = SIGCHLD;

	/* If we'd notified the old parent about this child's death,
	 * also notify the new parent.
	 */
R
Roland McGrath 已提交
810 811
	if (!ptrace_reparented(p) &&
	    p->exit_state == EXIT_ZOMBIE &&
812
	    !task_detached(p) && thread_group_empty(p))
813 814
		do_notify_parent(p, p->exit_signal);

815
	kill_orphaned_pgrp(p, father);
L
Linus Torvalds 已提交
816 817 818 819 820 821
}

/*
 * 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
822 823
 * the child reaper process (ie "init") in our pid
 * space.
L
Linus Torvalds 已提交
824
 */
825
static struct task_struct *find_new_reaper(struct task_struct *father)
L
Linus Torvalds 已提交
826
{
827 828
	struct pid_namespace *pid_ns = task_active_pid_ns(father);
	struct task_struct *thread;
L
Linus Torvalds 已提交
829

830 831 832 833 834 835 836 837
	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;
	}
L
Linus Torvalds 已提交
838

839 840 841 842
	if (unlikely(pid_ns->child_reaper == father)) {
		write_unlock_irq(&tasklist_lock);
		if (unlikely(pid_ns == &init_pid_ns))
			panic("Attempted to kill init!");
L
Linus Torvalds 已提交
843

844 845
		zap_pid_ns_processes(pid_ns);
		write_lock_irq(&tasklist_lock);
L
Linus Torvalds 已提交
846
		/*
847 848 849
		 * We can not clear ->child_reaper or leave it alone.
		 * There may by stealth EXIT_DEAD tasks on ->children,
		 * forget_original_parent() must move them somewhere.
L
Linus Torvalds 已提交
850
		 */
851
		pid_ns->child_reaper = init_pid_ns.child_reaper;
L
Linus Torvalds 已提交
852
	}
853

854 855 856
	return pid_ns->child_reaper;
}

857
static void forget_original_parent(struct task_struct *father)
L
Linus Torvalds 已提交
858
{
859
	struct task_struct *p, *n, *reaper;
R
Roland McGrath 已提交
860
	LIST_HEAD(ptrace_dead);
861 862

	write_lock_irq(&tasklist_lock);
863
	reaper = find_new_reaper(father);
R
Roland McGrath 已提交
864 865 866 867 868
	/*
	 * First clean up ptrace if we were using it.
	 */
	ptrace_exit(father, &ptrace_dead);

869
	list_for_each_entry_safe(p, n, &father->children, sibling) {
870
		p->real_parent = reaper;
R
Roland McGrath 已提交
871 872 873 874 875
		if (p->parent == father) {
			BUG_ON(p->ptrace);
			p->parent = p->real_parent;
		}
		reparent_thread(p, father);
L
Linus Torvalds 已提交
876
	}
877 878 879 880

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

R
Roland McGrath 已提交
881
	ptrace_exit_finish(father, &ptrace_dead);
L
Linus Torvalds 已提交
882 883 884 885 886 887
}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
888
static void exit_notify(struct task_struct *tsk, int group_dead)
L
Linus Torvalds 已提交
889
{
R
Roland McGrath 已提交
890 891
	int signal;
	void *cookie;
L
Linus Torvalds 已提交
892 893 894 895 896 897 898 899 900

	/*
	 * 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)
	 */
901
	forget_original_parent(tsk);
902
	exit_task_namespaces(tsk);
L
Linus Torvalds 已提交
903

904
	write_lock_irq(&tasklist_lock);
905 906
	if (group_dead)
		kill_orphaned_pgrp(tsk->group_leader, NULL);
L
Linus Torvalds 已提交
907

908
	/* Let father know we died
L
Linus Torvalds 已提交
909 910
	 *
	 * Thread signals are configurable, but you aren't going to use
911
	 * that to send signals to arbitary processes.
L
Linus Torvalds 已提交
912 913 914 915 916 917 918 919 920 921
	 * 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.
	 */
922
	if (tsk->exit_signal != SIGCHLD && !task_detached(tsk) &&
923
	    (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
924 925
	     tsk->self_exec_id != tsk->parent_exec_id) &&
	    !capable(CAP_KILL))
L
Linus Torvalds 已提交
926 927
		tsk->exit_signal = SIGCHLD;

R
Roland McGrath 已提交
928
	signal = tracehook_notify_death(tsk, &cookie, group_dead);
929
	if (signal >= 0)
R
Roland McGrath 已提交
930
		signal = do_notify_parent(tsk, signal);
L
Linus Torvalds 已提交
931

932
	tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE;
L
Linus Torvalds 已提交
933

934
	/* mt-exec, de_thread() is waiting for us */
935
	if (thread_group_leader(tsk) &&
936 937
	    tsk->signal->group_exit_task &&
	    tsk->signal->notify_count < 0)
938 939
		wake_up_process(tsk->signal->group_exit_task);

L
Linus Torvalds 已提交
940 941
	write_unlock_irq(&tasklist_lock);

R
Roland McGrath 已提交
942 943
	tracehook_report_death(tsk, signal, cookie, group_dead);

L
Linus Torvalds 已提交
944
	/* If the process is dead, release it - nobody will wait for it */
945
	if (signal == DEATH_REAP)
L
Linus Torvalds 已提交
946 947 948
		release_task(tsk);
}

949 950 951 952 953 954 955
#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;

956
	free = stack_not_used(current);
957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973

	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

974
NORET_TYPE void do_exit(long code)
L
Linus Torvalds 已提交
975 976 977 978 979 980
{
	struct task_struct *tsk = current;
	int group_dead;

	profile_task_exit(tsk);

981 982
	WARN_ON(atomic_read(&tsk->fs_excl));

L
Linus Torvalds 已提交
983 984 985 986 987
	if (unlikely(in_interrupt()))
		panic("Aiee, killing interrupt handler!");
	if (unlikely(!tsk->pid))
		panic("Attempted to kill the idle task!");

R
Roland McGrath 已提交
988
	tracehook_report_exit(&code);
L
Linus Torvalds 已提交
989

990 991 992 993 994 995 996
	/*
	 * 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");
997 998 999 1000 1001 1002 1003 1004 1005 1006
		/*
		 * 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;
1007 1008 1009 1010
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule();
	}

O
Oleg Nesterov 已提交
1011
	exit_signals(tsk);  /* sets PF_EXITING */
1012 1013 1014 1015
	/*
	 * tsk->flags are checked in the futex code to protect against
	 * an exiting task cleaning up the robust pi futexes.
	 */
1016 1017
	smp_mb();
	spin_unlock_wait(&tsk->pi_lock);
L
Linus Torvalds 已提交
1018 1019 1020

	if (unlikely(in_atomic()))
		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
1021
				current->comm, task_pid_nr(current),
L
Linus Torvalds 已提交
1022 1023 1024
				preempt_count());

	acct_update_integrals(tsk);
1025

L
Linus Torvalds 已提交
1026
	group_dead = atomic_dec_and_test(&tsk->signal->live);
1027
	if (group_dead) {
1028
		hrtimer_cancel(&tsk->signal->real_timer);
1029
		exit_itimers(tsk->signal);
1030
	}
1031
	acct_collect(code, group_dead);
M
Miloslav Trmac 已提交
1032 1033
	if (group_dead)
		tty_audit_exit();
1034 1035
	if (unlikely(tsk->audit_context))
		audit_free(tsk);
1036

1037
	tsk->exit_code = code;
1038
	taskstats_exit(tsk, group_dead);
1039

L
Linus Torvalds 已提交
1040 1041
	exit_mm(tsk);

1042
	if (group_dead)
1043
		acct_process();
1044 1045
	trace_sched_process_exit(tsk);

L
Linus Torvalds 已提交
1046
	exit_sem(tsk);
1047 1048
	exit_files(tsk);
	exit_fs(tsk);
1049
	check_stack_usage();
L
Linus Torvalds 已提交
1050
	exit_thread();
1051
	cgroup_exit(tsk, 1);
L
Linus Torvalds 已提交
1052 1053 1054 1055

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

A
Al Viro 已提交
1056
	module_put(task_thread_info(tsk)->exec_domain->module);
L
Linus Torvalds 已提交
1057 1058 1059
	if (tsk->binfmt)
		module_put(tsk->binfmt->module);

M
Matt Helsley 已提交
1060
	proc_exit_connector(tsk);
1061
	exit_notify(tsk, group_dead);
L
Linus Torvalds 已提交
1062
#ifdef CONFIG_NUMA
1063
	mpol_put(tsk->mempolicy);
L
Linus Torvalds 已提交
1064 1065
	tsk->mempolicy = NULL;
#endif
1066
#ifdef CONFIG_FUTEX
1067 1068 1069 1070 1071 1072 1073 1074
	/*
	 * 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);
1075
#endif
1076
	/*
1077
	 * Make sure we are holding no locks:
1078
	 */
1079
	debug_check_no_locks_held(tsk);
1080 1081 1082 1083 1084 1085
	/*
	 * 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
1086

1087 1088 1089
	if (tsk->io_context)
		exit_io_context();

1090 1091 1092
	if (tsk->splice_pipe)
		__free_pipe_info(tsk->splice_pipe);

C
Coywolf Qi Hunt 已提交
1093
	preempt_disable();
O
Oleg Nesterov 已提交
1094
	/* causes final put_task_struct in finish_task_switch(). */
1095
	tsk->state = TASK_DEAD;
L
Linus Torvalds 已提交
1096 1097 1098
	schedule();
	BUG();
	/* Avoid "noreturn function does return".  */
A
Alan Cox 已提交
1099 1100
	for (;;)
		cpu_relax();	/* For when BUG is null */
L
Linus Torvalds 已提交
1101 1102
}

1103 1104
EXPORT_SYMBOL_GPL(do_exit);

L
Linus Torvalds 已提交
1105 1106 1107 1108
NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
	if (comp)
		complete(comp);
O
Oleg Nesterov 已提交
1109

L
Linus Torvalds 已提交
1110 1111 1112 1113 1114
	do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

1115
SYSCALL_DEFINE1(exit, int, error_code)
L
Linus Torvalds 已提交
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
{
	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)
{
1127 1128
	struct signal_struct *sig = current->signal;

L
Linus Torvalds 已提交
1129 1130
	BUG_ON(exit_code & 0x80); /* core dumps don't get here */

1131 1132
	if (signal_group_exit(sig))
		exit_code = sig->group_exit_code;
L
Linus Torvalds 已提交
1133 1134 1135
	else if (!thread_group_empty(current)) {
		struct sighand_struct *const sighand = current->sighand;
		spin_lock_irq(&sighand->siglock);
1136
		if (signal_group_exit(sig))
L
Linus Torvalds 已提交
1137 1138 1139 1140
			/* Another thread got here before we took the lock.  */
			exit_code = sig->group_exit_code;
		else {
			sig->group_exit_code = exit_code;
1141
			sig->flags = SIGNAL_GROUP_EXIT;
L
Linus Torvalds 已提交
1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155
			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.
 */
1156
SYSCALL_DEFINE1(exit_group, int, error_code)
L
Linus Torvalds 已提交
1157 1158
{
	do_group_exit((error_code & 0xff) << 8);
1159 1160
	/* NOTREACHED */
	return 0;
L
Linus Torvalds 已提交
1161 1162
}

E
Eric W. Biederman 已提交
1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174
static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
{
	struct pid *pid = NULL;
	if (type == PIDTYPE_PID)
		pid = task->pids[type].pid;
	else if (type < PIDTYPE_MAX)
		pid = task->group_leader->pids[type].pid;
	return pid;
}

static int eligible_child(enum pid_type type, struct pid *pid, int options,
			  struct task_struct *p)
L
Linus Torvalds 已提交
1175
{
1176 1177
	int err;

E
Eric W. Biederman 已提交
1178 1179
	if (type < PIDTYPE_MAX) {
		if (task_pid_type(p, type) != pid)
L
Linus Torvalds 已提交
1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
			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;

1192
	err = security_task_wait(p);
1193 1194
	if (err)
		return err;
L
Linus Torvalds 已提交
1195

1196
	return 1;
L
Linus Torvalds 已提交
1197 1198
}

1199
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
L
Linus Torvalds 已提交
1200 1201 1202 1203 1204
			       int why, int status,
			       struct siginfo __user *infop,
			       struct rusage __user *rusagep)
{
	int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1205

L
Linus Torvalds 已提交
1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229
	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.
 */
R
Roland McGrath 已提交
1230
static int wait_task_zombie(struct task_struct *p, int options,
L
Linus Torvalds 已提交
1231 1232 1233 1234
			    struct siginfo __user *infop,
			    int __user *stat_addr, struct rusage __user *ru)
{
	unsigned long state;
1235
	int retval, status, traced;
1236
	pid_t pid = task_pid_vnr(p);
1237
	uid_t uid = __task_cred(p)->uid;
L
Linus Torvalds 已提交
1238

R
Roland McGrath 已提交
1239 1240 1241 1242
	if (!likely(options & WEXITED))
		return 0;

	if (unlikely(options & WNOWAIT)) {
L
Linus Torvalds 已提交
1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268
		int exit_code = p->exit_code;
		int why, status;

		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;
	}

1269
	traced = ptrace_reparented(p);
1270 1271

	if (likely(!traced)) {
1272 1273
		struct signal_struct *psig;
		struct signal_struct *sig;
1274
		struct task_cputime cputime;
1275

L
Linus Torvalds 已提交
1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
		/*
		 * 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.
1290 1291 1292 1293
		 *
		 * We use thread_group_cputime() to get times for the thread
		 * group, which consolidates times for all threads in the
		 * group including the group leader.
L
Linus Torvalds 已提交
1294
		 */
1295
		thread_group_cputime(p, &cputime);
L
Linus Torvalds 已提交
1296
		spin_lock_irq(&p->parent->sighand->siglock);
1297 1298 1299 1300
		psig = p->parent->signal;
		sig = p->signal;
		psig->cutime =
			cputime_add(psig->cutime,
1301 1302
			cputime_add(cputime.utime,
				    sig->cutime));
1303 1304
		psig->cstime =
			cputime_add(psig->cstime,
1305 1306
			cputime_add(cputime.stime,
				    sig->cstime));
1307 1308 1309 1310 1311
		psig->cgtime =
			cputime_add(psig->cgtime,
			cputime_add(p->gtime,
			cputime_add(sig->gtime,
				    sig->cgtime)));
1312 1313 1314 1315 1316 1317 1318 1319
		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;
1320 1321 1322 1323 1324 1325
		psig->cinblock +=
			task_io_get_inblock(p) +
			sig->inblock + sig->cinblock;
		psig->coublock +=
			task_io_get_oublock(p) +
			sig->oublock + sig->coublock;
1326 1327
		task_io_accounting_add(&psig->ioac, &p->ioac);
		task_io_accounting_add(&psig->ioac, &sig->ioac);
L
Linus Torvalds 已提交
1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360
		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)
1361
		retval = put_user(pid, &infop->si_pid);
L
Linus Torvalds 已提交
1362
	if (!retval && infop)
1363
		retval = put_user(uid, &infop->si_uid);
1364
	if (!retval)
1365
		retval = pid;
1366 1367

	if (traced) {
L
Linus Torvalds 已提交
1368
		write_lock_irq(&tasklist_lock);
1369 1370 1371 1372 1373 1374 1375
		/* 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.
		 */
1376
		if (!task_detached(p)) {
1377
			do_notify_parent(p, p->exit_signal);
1378
			if (!task_detached(p)) {
1379 1380
				p->exit_state = EXIT_ZOMBIE;
				p = NULL;
L
Linus Torvalds 已提交
1381 1382 1383 1384 1385 1386
			}
		}
		write_unlock_irq(&tasklist_lock);
	}
	if (p != NULL)
		release_task(p);
1387

L
Linus Torvalds 已提交
1388 1389 1390 1391 1392 1393 1394 1395 1396
	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.
 */
R
Roland McGrath 已提交
1397
static int wait_task_stopped(int ptrace, struct task_struct *p,
R
Roland McGrath 已提交
1398
			     int options, struct siginfo __user *infop,
L
Linus Torvalds 已提交
1399 1400
			     int __user *stat_addr, struct rusage __user *ru)
{
1401 1402
	int retval, exit_code, why;
	uid_t uid = 0; /* unneeded, required by compiler */
1403
	pid_t pid;
L
Linus Torvalds 已提交
1404

R
Roland McGrath 已提交
1405
	if (!(options & WUNTRACED))
R
Roland McGrath 已提交
1406 1407
		return 0;

1408 1409 1410 1411 1412 1413
	exit_code = 0;
	spin_lock_irq(&p->sighand->siglock);

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

R
Roland McGrath 已提交
1414
	if (!ptrace && p->signal->group_stop_count > 0)
L
Linus Torvalds 已提交
1415 1416 1417 1418
		/*
		 * A group stop is in progress and this is the group leader.
		 * We won't report until all threads have stopped.
		 */
1419 1420 1421 1422 1423 1424
		goto unlock_sig;

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

R
Roland McGrath 已提交
1425
	if (!unlikely(options & WNOWAIT))
1426 1427
		p->exit_code = 0;

1428 1429
	/* don't need the RCU readlock here as we're holding a spinlock */
	uid = __task_cred(p)->uid;
1430 1431 1432
unlock_sig:
	spin_unlock_irq(&p->sighand->siglock);
	if (!exit_code)
L
Linus Torvalds 已提交
1433 1434 1435 1436 1437 1438 1439 1440 1441 1442
		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);
1443
	pid = task_pid_vnr(p);
R
Roland McGrath 已提交
1444
	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
L
Linus Torvalds 已提交
1445 1446
	read_unlock(&tasklist_lock);

R
Roland McGrath 已提交
1447
	if (unlikely(options & WNOWAIT))
L
Linus Torvalds 已提交
1448
		return wait_noreap_copyout(p, pid, uid,
1449
					   why, exit_code,
L
Linus Torvalds 已提交
1450 1451 1452 1453 1454 1455 1456 1457 1458 1459
					   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)
R
Roland McGrath 已提交
1460
		retval = put_user((short)why, &infop->si_code);
L
Linus Torvalds 已提交
1461 1462 1463
	if (!retval && infop)
		retval = put_user(exit_code, &infop->si_status);
	if (!retval && infop)
1464
		retval = put_user(pid, &infop->si_pid);
L
Linus Torvalds 已提交
1465
	if (!retval && infop)
1466
		retval = put_user(uid, &infop->si_uid);
L
Linus Torvalds 已提交
1467
	if (!retval)
1468
		retval = pid;
L
Linus Torvalds 已提交
1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480
	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.
 */
R
Roland McGrath 已提交
1481
static int wait_task_continued(struct task_struct *p, int options,
L
Linus Torvalds 已提交
1482 1483 1484 1485 1486 1487 1488
			       struct siginfo __user *infop,
			       int __user *stat_addr, struct rusage __user *ru)
{
	int retval;
	pid_t pid;
	uid_t uid;

R
Roland McGrath 已提交
1489 1490 1491
	if (!unlikely(options & WCONTINUED))
		return 0;

L
Linus Torvalds 已提交
1492 1493 1494 1495 1496 1497 1498 1499 1500
	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;
	}
R
Roland McGrath 已提交
1501
	if (!unlikely(options & WNOWAIT))
L
Linus Torvalds 已提交
1502
		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1503
	uid = __task_cred(p)->uid;
L
Linus Torvalds 已提交
1504 1505
	spin_unlock_irq(&p->sighand->siglock);

1506
	pid = task_pid_vnr(p);
L
Linus Torvalds 已提交
1507 1508 1509 1510 1511 1512 1513 1514 1515
	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)
1516
			retval = pid;
L
Linus Torvalds 已提交
1517 1518 1519 1520 1521 1522 1523 1524 1525 1526
	} else {
		retval = wait_noreap_copyout(p, pid, uid,
					     CLD_CONTINUED, SIGCONT,
					     infop, ru);
		BUG_ON(retval == 0);
	}

	return retval;
}

R
Roland McGrath 已提交
1527 1528 1529 1530 1531 1532
/*
 * 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;
1533 1534
 * then *@notask_error is 0 if @p is an eligible child,
 * or another error from security_task_wait(), or still -ECHILD.
R
Roland McGrath 已提交
1535
 */
R
Roland McGrath 已提交
1536
static int wait_consider_task(struct task_struct *parent, int ptrace,
R
Roland McGrath 已提交
1537 1538 1539 1540 1541 1542
			      struct task_struct *p, int *notask_error,
			      enum pid_type type, struct pid *pid, int options,
			      struct siginfo __user *infop,
			      int __user *stat_addr, struct rusage __user *ru)
{
	int ret = eligible_child(type, pid, options, p);
1543
	if (!ret)
R
Roland McGrath 已提交
1544 1545
		return ret;

1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557
	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 (*notask_error)
			*notask_error = ret;
	}

R
Roland McGrath 已提交
1558 1559 1560 1561 1562 1563 1564 1565 1566
	if (likely(!ptrace) && unlikely(p->ptrace)) {
		/*
		 * This child is hidden by ptrace.
		 * We aren't allowed to see it now, but eventually we will.
		 */
		*notask_error = 0;
		return 0;
	}

R
Roland McGrath 已提交
1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582
	if (p->exit_state == EXIT_DEAD)
		return 0;

	/*
	 * We don't reap group leaders with subthreads.
	 */
	if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
		return wait_task_zombie(p, options, infop, stat_addr, ru);

	/*
	 * It's stopped or running now, so it might
	 * later continue, exit, or stop again.
	 */
	*notask_error = 0;

	if (task_is_stopped_or_traced(p))
R
Roland McGrath 已提交
1583 1584
		return wait_task_stopped(ptrace, p, options,
					 infop, stat_addr, ru);
R
Roland McGrath 已提交
1585 1586 1587 1588 1589 1590 1591 1592 1593 1594

	return wait_task_continued(p, options, infop, stat_addr, ru);
}

/*
 * 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
1595 1596
 * *@notask_error is 0 if there were any eligible children,
 * or another error from security_task_wait(), or still -ECHILD.
R
Roland McGrath 已提交
1597 1598 1599 1600 1601 1602 1603 1604 1605
 */
static int do_wait_thread(struct task_struct *tsk, int *notask_error,
			  enum pid_type type, struct pid *pid, int options,
			  struct siginfo __user *infop, int __user *stat_addr,
			  struct rusage __user *ru)
{
	struct task_struct *p;

	list_for_each_entry(p, &tsk->children, sibling) {
R
Roland McGrath 已提交
1606 1607 1608 1609 1610 1611 1612 1613 1614 1615
		/*
		 * Do not consider detached threads.
		 */
		if (!task_detached(p)) {
			int ret = wait_consider_task(tsk, 0, p, notask_error,
						     type, pid, options,
						     infop, stat_addr, ru);
			if (ret)
				return ret;
		}
R
Roland McGrath 已提交
1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628
	}

	return 0;
}

static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
			  enum pid_type type, struct pid *pid, int options,
			  struct siginfo __user *infop, int __user *stat_addr,
			  struct rusage __user *ru)
{
	struct task_struct *p;

	/*
R
Roland McGrath 已提交
1629
	 * Traditionally we see ptrace'd stopped tasks regardless of options.
R
Roland McGrath 已提交
1630
	 */
R
Roland McGrath 已提交
1631
	options |= WUNTRACED;
R
Roland McGrath 已提交
1632

R
Roland McGrath 已提交
1633 1634 1635 1636 1637
	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
		int ret = wait_consider_task(tsk, 1, p, notask_error,
					     type, pid, options,
					     infop, stat_addr, ru);
		if (ret)
R
Roland McGrath 已提交
1638 1639 1640 1641 1642 1643
			return ret;
	}

	return 0;
}

E
Eric W. Biederman 已提交
1644 1645 1646
static long do_wait(enum pid_type type, struct pid *pid, int options,
		    struct siginfo __user *infop, int __user *stat_addr,
		    struct rusage __user *ru)
L
Linus Torvalds 已提交
1647 1648 1649
{
	DECLARE_WAITQUEUE(wait, current);
	struct task_struct *tsk;
R
Roland McGrath 已提交
1650
	int retval;
L
Linus Torvalds 已提交
1651

1652 1653
	trace_sched_process_wait(pid);

L
Linus Torvalds 已提交
1654 1655
	add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
R
Roland McGrath 已提交
1656 1657 1658 1659 1660
	/*
	 * If there is nothing that can match our critiera just get out.
	 * We will clear @retval to zero if we see any child that might later
	 * match our criteria, even if we are not able to reap it yet.
	 */
E
Eric W. Biederman 已提交
1661 1662 1663 1664
	retval = -ECHILD;
	if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
		goto end;

L
Linus Torvalds 已提交
1665 1666 1667 1668
	current->state = TASK_INTERRUPTIBLE;
	read_lock(&tasklist_lock);
	tsk = current;
	do {
R
Roland McGrath 已提交
1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681
		int tsk_result = do_wait_thread(tsk, &retval,
						type, pid, options,
						infop, stat_addr, ru);
		if (!tsk_result)
			tsk_result = ptrace_do_wait(tsk, &retval,
						    type, pid, options,
						    infop, stat_addr, ru);
		if (tsk_result) {
			/*
			 * tasklist_lock is unlocked and we have a final result.
			 */
			retval = tsk_result;
			goto end;
L
Linus Torvalds 已提交
1682
		}
R
Roland McGrath 已提交
1683

L
Linus Torvalds 已提交
1684 1685 1686
		if (options & __WNOTHREAD)
			break;
		tsk = next_thread(tsk);
E
Eric Sesterhenn 已提交
1687
		BUG_ON(tsk->signal != current->signal);
L
Linus Torvalds 已提交
1688 1689
	} while (tsk != current);
	read_unlock(&tasklist_lock);
O
Oleg Nesterov 已提交
1690

R
Roland McGrath 已提交
1691
	if (!retval && !(options & WNOHANG)) {
L
Linus Torvalds 已提交
1692
		retval = -ERESTARTSYS;
R
Roland McGrath 已提交
1693 1694 1695 1696
		if (!signal_pending(current)) {
			schedule();
			goto repeat;
		}
L
Linus Torvalds 已提交
1697
	}
R
Roland McGrath 已提交
1698

L
Linus Torvalds 已提交
1699 1700 1701 1702 1703
end:
	current->state = TASK_RUNNING;
	remove_wait_queue(&current->signal->wait_chldexit,&wait);
	if (infop) {
		if (retval > 0)
1704
			retval = 0;
L
Linus Torvalds 已提交
1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727
		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;
}

1728 1729
SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
		infop, int, options, struct rusage __user *, ru)
L
Linus Torvalds 已提交
1730
{
E
Eric W. Biederman 已提交
1731 1732
	struct pid *pid = NULL;
	enum pid_type type;
L
Linus Torvalds 已提交
1733 1734 1735 1736 1737 1738 1739 1740 1741
	long ret;

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

	switch (which) {
	case P_ALL:
E
Eric W. Biederman 已提交
1742
		type = PIDTYPE_MAX;
L
Linus Torvalds 已提交
1743 1744
		break;
	case P_PID:
E
Eric W. Biederman 已提交
1745 1746
		type = PIDTYPE_PID;
		if (upid <= 0)
L
Linus Torvalds 已提交
1747 1748 1749
			return -EINVAL;
		break;
	case P_PGID:
E
Eric W. Biederman 已提交
1750 1751
		type = PIDTYPE_PGID;
		if (upid <= 0)
L
Linus Torvalds 已提交
1752 1753 1754 1755 1756 1757
			return -EINVAL;
		break;
	default:
		return -EINVAL;
	}

E
Eric W. Biederman 已提交
1758 1759 1760 1761
	if (type < PIDTYPE_MAX)
		pid = find_get_pid(upid);
	ret = do_wait(type, pid, options, infop, NULL, ru);
	put_pid(pid);
L
Linus Torvalds 已提交
1762 1763

	/* avoid REGPARM breakage on x86: */
1764
	asmlinkage_protect(5, ret, which, upid, infop, options, ru);
L
Linus Torvalds 已提交
1765 1766 1767
	return ret;
}

1768 1769
SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
		int, options, struct rusage __user *, ru)
L
Linus Torvalds 已提交
1770
{
E
Eric W. Biederman 已提交
1771 1772
	struct pid *pid = NULL;
	enum pid_type type;
L
Linus Torvalds 已提交
1773 1774 1775 1776 1777
	long ret;

	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
			__WNOTHREAD|__WCLONE|__WALL))
		return -EINVAL;
E
Eric W. Biederman 已提交
1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793

	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_pid(task_pgrp(current));
	} else /* upid > 0 */ {
		type = PIDTYPE_PID;
		pid = find_get_pid(upid);
	}

	ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
	put_pid(pid);
L
Linus Torvalds 已提交
1794 1795

	/* avoid REGPARM breakage on x86: */
1796
	asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
L
Linus Torvalds 已提交
1797 1798 1799 1800 1801 1802 1803 1804 1805
	return ret;
}

#ifdef __ARCH_WANT_SYS_WAITPID

/*
 * sys_waitpid() remains for compatibility. waitpid() should be
 * implemented by calling sys_wait4() from libc.a.
 */
1806
SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
L
Linus Torvalds 已提交
1807 1808 1809 1810 1811
{
	return sys_wait4(pid, stat_addr, options, NULL);
}

#endif