exit.c 46.4 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/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/fs_struct.h>
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#include <linux/init_task.h>
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#include <linux/perf_event.h>
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#include <trace/events/sched.h>
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#include <linux/hw_breakpoint.h>
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#include <linux/oom.h>
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#include <linux/writeback.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, bool group_dead)
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{
	nr_threads--;
	detach_pid(p, PIDTYPE_PID);
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	if (group_dead) {
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		detach_pid(p, PIDTYPE_PGID);
		detach_pid(p, PIDTYPE_SID);
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		list_del_rcu(&p->tasks);
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		list_del_init(&p->sibling);
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		__this_cpu_dec(process_counts);
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	}
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	list_del_rcu(&p->thread_group);
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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;
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	bool group_dead = thread_group_leader(tsk);
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	struct sighand_struct *sighand;
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	struct tty_struct *uninitialized_var(tty);
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	sighand = rcu_dereference_check(tsk->sighand,
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					lockdep_tasklist_lock_is_held());
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	spin_lock(&sighand->siglock);

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

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		/*
		 * If there is any task waiting for the group exit
		 * then notify it:
		 */
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		if (sig->notify_count > 0 && !--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 += tsk->utime;
		sig->stime += tsk->stime;
		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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		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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	}

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	sig->nr_threads--;
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	__unhash_process(tsk, group_dead);
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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->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);
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	if (group_dead) {
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		flush_sigqueue(&sig->shared_pending);
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		tty_kref_put(tty);
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	}
}

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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);

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	perf_event_delayed_put(tsk);
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	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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	/* don't need to get the RCU readlock here - the process is dead and
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	 * can't be modifying its own credentials. But shut RCU-lockdep up */
	rcu_read_lock();
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	atomic_dec(&__task_cred(p)->user->processes);
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	rcu_read_unlock();
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	proc_flush_task(p);
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	write_lock_irq(&tasklist_lock);
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	ptrace_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) {
		/*
		 * 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.
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		 */
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		zap_leader = do_notify_parent(leader, leader->exit_signal);
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		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 bool has_stopped_jobs(struct pid *pgrp)
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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->signal->flags & SIGNAL_STOP_STOPPED)
			return true;
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	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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	return false;
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}

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

/*
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 * Let kernel threads use this to say that they allow a certain signal.
 * Must not be used if kthread was cloned with CLONE_SIGHAND.
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 */
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);
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	/* This is only needed for daemonize()'ed kthreads */
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	sigdelset(&current->blocked, sig);
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	/*
	 * 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;
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	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
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	 * files structure.  But use RCU to shut RCU-lockdep up.
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	 */
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	rcu_read_lock();
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	fdt = files_fdtable(files);
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	rcu_read_unlock();
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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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		rcu_read_lock();
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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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		rcu_read_unlock();
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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
/*
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 * A task is exiting.   If it owned this mm, find a new owner for the mm.
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 */
void mm_update_next_owner(struct mm_struct *mm)
{
	struct task_struct *c, *g, *p = current;

retry:
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	/*
	 * If the exiting or execing task is not the owner, it's
	 * someone else's problem.
	 */
	if (mm->owner != p)
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		return;
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	/*
	 * The current owner is exiting/execing and there are no other
	 * candidates.  Do not leave the mm pointing to a possibly
	 * freed task structure.
	 */
	if (atomic_read(&mm->mm_users) <= 1) {
		mm->owner = NULL;
		return;
	}
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	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
	 */
586
	list_for_each_entry(c, &p->real_parent->children, sibling) {
587 588 589 590 591 592 593 594 595 596 597 598 599 600
		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);
601 602 603
	/*
	 * We found no owner yet mm_users > 1: this implies that we are
	 * most likely racing with swapoff (try_to_unuse()) or /proc or
604
	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
605 606
	 */
	mm->owner = NULL;
607 608 609 610 611 612 613 614 615 616
	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);
617 618 619 620 621
	/*
	 * Delay read_unlock() till we have the task_lock()
	 * to ensure that c does not slip away underneath us
	 */
	read_unlock(&tasklist_lock);
622 623 624 625 626 627 628 629 630 631 632
	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
633 634 635 636
/*
 * Turn us into a lazy TLB process if we
 * aren't already..
 */
A
Adrian Bunk 已提交
637
static void exit_mm(struct task_struct * tsk)
L
Linus Torvalds 已提交
638 639
{
	struct mm_struct *mm = tsk->mm;
640
	struct core_state *core_state;
L
Linus Torvalds 已提交
641 642 643 644 645 646

	mm_release(tsk, mm);
	if (!mm)
		return;
	/*
	 * Serialize with any possible pending coredump.
647
	 * We must hold mmap_sem around checking core_state
L
Linus Torvalds 已提交
648
	 * and clearing tsk->mm.  The core-inducing thread
649
	 * will increment ->nr_threads for each thread in the
L
Linus Torvalds 已提交
650 651 652
	 * group with ->mm != NULL.
	 */
	down_read(&mm->mmap_sem);
653 654 655
	core_state = mm->core_state;
	if (core_state) {
		struct core_thread self;
L
Linus Torvalds 已提交
656 657
		up_read(&mm->mmap_sem);

658 659 660 661 662 663 664 665
		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
666

O
Oleg Nesterov 已提交
667 668 669 670 671 672 673
		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
674 675 676
		down_read(&mm->mmap_sem);
	}
	atomic_inc(&mm->mm_count);
E
Eric Sesterhenn 已提交
677
	BUG_ON(mm != tsk->active_mm);
L
Linus Torvalds 已提交
678 679 680 681 682 683
	/* more a memory barrier than a real lock */
	task_lock(tsk);
	tsk->mm = NULL;
	up_read(&mm->mmap_sem);
	enter_lazy_tlb(mm, current);
	task_unlock(tsk);
684
	mm_update_next_owner(mm);
L
Linus Torvalds 已提交
685 686 687 688 689 690 691
	mmput(mm);
}

/*
 * 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
692 693
 * the child reaper process (ie "init") in our pid
 * space.
L
Linus Torvalds 已提交
694
 */
695
static struct task_struct *find_new_reaper(struct task_struct *father)
696 697
	__releases(&tasklist_lock)
	__acquires(&tasklist_lock)
L
Linus Torvalds 已提交
698
{
699 700
	struct pid_namespace *pid_ns = task_active_pid_ns(father);
	struct task_struct *thread;
L
Linus Torvalds 已提交
701

702 703 704 705 706 707 708 709
	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
710

711 712 713 714
	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
715

716 717
		zap_pid_ns_processes(pid_ns);
		write_lock_irq(&tasklist_lock);
L
Linus Torvalds 已提交
718
		/*
719 720 721
		 * 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
722
		 */
723
		pid_ns->child_reaper = init_pid_ns.child_reaper;
L
Linus Torvalds 已提交
724
	}
725

726 727 728
	return pid_ns->child_reaper;
}

729 730 731
/*
* Any that need to be release_task'd are put on the @dead list.
 */
732
static void reparent_leader(struct task_struct *father, struct task_struct *p,
733 734 735 736
				struct list_head *dead)
{
	list_move_tail(&p->sibling, &p->real_parent->children);

737
	if (p->exit_state == EXIT_DEAD)
738 739 740 741 742 743 744 745 746 747 748 749
		return;
	/*
	 * If this is a threaded reparent there is no need to
	 * notify anyone anything has happened.
	 */
	if (same_thread_group(p->real_parent, father))
		return;

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

	/* If it has exited notify the new parent about this child's death. */
T
Tejun Heo 已提交
750
	if (!p->ptrace &&
751
	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
752
		if (do_notify_parent(p, p->exit_signal)) {
753 754 755 756 757 758 759 760
			p->exit_state = EXIT_DEAD;
			list_move_tail(&p->sibling, dead);
		}
	}

	kill_orphaned_pgrp(p, father);
}

761
static void forget_original_parent(struct task_struct *father)
L
Linus Torvalds 已提交
762
{
763
	struct task_struct *p, *n, *reaper;
764
	LIST_HEAD(dead_children);
765 766

	write_lock_irq(&tasklist_lock);
767 768 769 770 771
	/*
	 * Note that exit_ptrace() and find_new_reaper() might
	 * drop tasklist_lock and reacquire it.
	 */
	exit_ptrace(father);
772
	reaper = find_new_reaper(father);
R
Roland McGrath 已提交
773

774
	list_for_each_entry_safe(p, n, &father->children, sibling) {
775 776 777 778
		struct task_struct *t = p;
		do {
			t->real_parent = reaper;
			if (t->parent == father) {
T
Tejun Heo 已提交
779
				BUG_ON(t->ptrace);
780 781 782 783 784 785 786
				t->parent = t->real_parent;
			}
			if (t->pdeath_signal)
				group_send_sig_info(t->pdeath_signal,
						    SEND_SIG_NOINFO, t);
		} while_each_thread(p, t);
		reparent_leader(father, p, &dead_children);
L
Linus Torvalds 已提交
787
	}
788
	write_unlock_irq(&tasklist_lock);
789

790 791
	BUG_ON(!list_empty(&father->children));

792 793
	list_for_each_entry_safe(p, n, &dead_children, sibling) {
		list_del_init(&p->sibling);
794 795
		release_task(p);
	}
L
Linus Torvalds 已提交
796 797 798 799 800 801
}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
802
static void exit_notify(struct task_struct *tsk, int group_dead)
L
Linus Torvalds 已提交
803
{
804
	bool autoreap;
L
Linus Torvalds 已提交
805 806 807 808 809 810 811 812 813

	/*
	 * 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)
	 */
814
	forget_original_parent(tsk);
815
	exit_task_namespaces(tsk);
L
Linus Torvalds 已提交
816

817
	write_lock_irq(&tasklist_lock);
818 819
	if (group_dead)
		kill_orphaned_pgrp(tsk->group_leader, NULL);
L
Linus Torvalds 已提交
820

821
	/* Let father know we died
L
Linus Torvalds 已提交
822 823
	 *
	 * Thread signals are configurable, but you aren't going to use
L
Lucas De Marchi 已提交
824
	 * that to send signals to arbitrary processes.
L
Linus Torvalds 已提交
825 826 827 828 829 830 831 832 833 834
	 * 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.
	 */
O
Oleg Nesterov 已提交
835
	if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD &&
836
	    (tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
837
	     tsk->self_exec_id != tsk->parent_exec_id))
L
Linus Torvalds 已提交
838 839
		tsk->exit_signal = SIGCHLD;

O
Oleg Nesterov 已提交
840 841 842 843 844 845 846 847 848 849 850 851
	if (unlikely(tsk->ptrace)) {
		int sig = thread_group_leader(tsk) &&
				thread_group_empty(tsk) &&
				!ptrace_reparented(tsk) ?
			tsk->exit_signal : SIGCHLD;
		autoreap = do_notify_parent(tsk, sig);
	} else if (thread_group_leader(tsk)) {
		autoreap = thread_group_empty(tsk) &&
			do_notify_parent(tsk, tsk->exit_signal);
	} else {
		autoreap = true;
	}
L
Linus Torvalds 已提交
852

853
	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
L
Linus Torvalds 已提交
854

855 856
	/* mt-exec, de_thread() is waiting for group leader */
	if (unlikely(tsk->signal->notify_count < 0))
857
		wake_up_process(tsk->signal->group_exit_task);
L
Linus Torvalds 已提交
858 859 860
	write_unlock_irq(&tasklist_lock);

	/* If the process is dead, release it - nobody will wait for it */
861
	if (autoreap)
L
Linus Torvalds 已提交
862 863 864
		release_task(tsk);
}

865 866 867 868 869 870 871
#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;

872
	free = stack_not_used(current);
873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889

	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

890
void do_exit(long code)
L
Linus Torvalds 已提交
891 892 893 894 895 896
{
	struct task_struct *tsk = current;
	int group_dead;

	profile_task_exit(tsk);

897
	WARN_ON(blk_needs_flush_plug(tsk));
898

L
Linus Torvalds 已提交
899 900 901 902 903
	if (unlikely(in_interrupt()))
		panic("Aiee, killing interrupt handler!");
	if (unlikely(!tsk->pid))
		panic("Attempted to kill the idle task!");

904 905 906 907 908 909 910 911 912
	/*
	 * If do_exit is called because this processes oopsed, it's possible
	 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
	 * continuing. Amongst other possible reasons, this is to prevent
	 * mm_release()->clear_child_tid() from writing to a user-controlled
	 * kernel address.
	 */
	set_fs(USER_DS);

T
Tejun Heo 已提交
913
	ptrace_event(PTRACE_EVENT_EXIT, code);
L
Linus Torvalds 已提交
914

915 916
	validate_creds_for_do_exit(tsk);

917 918 919 920 921 922 923
	/*
	 * 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");
924 925 926 927 928 929 930 931 932 933
		/*
		 * 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;
934 935 936 937
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule();
	}

938 939
	exit_irq_thread();

O
Oleg Nesterov 已提交
940
	exit_signals(tsk);  /* sets PF_EXITING */
941 942 943 944
	/*
	 * tsk->flags are checked in the futex code to protect against
	 * an exiting task cleaning up the robust pi futexes.
	 */
945
	smp_mb();
946
	raw_spin_unlock_wait(&tsk->pi_lock);
L
Linus Torvalds 已提交
947 948 949

	if (unlikely(in_atomic()))
		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
950
				current->comm, task_pid_nr(current),
L
Linus Torvalds 已提交
951 952 953
				preempt_count());

	acct_update_integrals(tsk);
954
	/* sync mm's RSS info before statistics gathering */
955 956
	if (tsk->mm)
		sync_mm_rss(tsk, tsk->mm);
L
Linus Torvalds 已提交
957
	group_dead = atomic_dec_and_test(&tsk->signal->live);
958
	if (group_dead) {
959
		hrtimer_cancel(&tsk->signal->real_timer);
960
		exit_itimers(tsk->signal);
J
Jiri Pirko 已提交
961 962
		if (tsk->mm)
			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
963
	}
964
	acct_collect(code, group_dead);
M
Miloslav Trmac 已提交
965 966
	if (group_dead)
		tty_audit_exit();
967
	audit_free(tsk);
968

969
	tsk->exit_code = code;
970
	taskstats_exit(tsk, group_dead);
971

L
Linus Torvalds 已提交
972 973
	exit_mm(tsk);

974
	if (group_dead)
975
		acct_process();
976 977
	trace_sched_process_exit(tsk);

L
Linus Torvalds 已提交
978
	exit_sem(tsk);
979
	exit_shm(tsk);
980 981
	exit_files(tsk);
	exit_fs(tsk);
982
	check_stack_usage();
L
Linus Torvalds 已提交
983
	exit_thread();
984 985 986 987 988 989 990 991 992

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

993
	cgroup_exit(tsk, 1);
L
Linus Torvalds 已提交
994

995
	if (group_dead)
L
Linus Torvalds 已提交
996 997
		disassociate_ctty(1);

A
Al Viro 已提交
998
	module_put(task_thread_info(tsk)->exec_domain->module);
L
Linus Torvalds 已提交
999

M
Matt Helsley 已提交
1000
	proc_exit_connector(tsk);
1001

1002 1003 1004
	/*
	 * FIXME: do that only when needed, using sched_exit tracepoint
	 */
1005
	ptrace_put_breakpoints(tsk);
1006

1007
	exit_notify(tsk, group_dead);
L
Linus Torvalds 已提交
1008
#ifdef CONFIG_NUMA
1009
	task_lock(tsk);
1010
	mpol_put(tsk->mempolicy);
L
Linus Torvalds 已提交
1011
	tsk->mempolicy = NULL;
1012
	task_unlock(tsk);
L
Linus Torvalds 已提交
1013
#endif
1014
#ifdef CONFIG_FUTEX
1015 1016
	if (unlikely(current->pi_state_cache))
		kfree(current->pi_state_cache);
1017
#endif
1018
	/*
1019
	 * Make sure we are holding no locks:
1020
	 */
1021
	debug_check_no_locks_held(tsk);
1022 1023 1024 1025 1026 1027
	/*
	 * 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
1028

1029
	if (tsk->io_context)
1030
		exit_io_context(tsk);
1031

1032 1033 1034
	if (tsk->splice_pipe)
		__free_pipe_info(tsk->splice_pipe);

1035 1036
	validate_creds_for_do_exit(tsk);

C
Coywolf Qi Hunt 已提交
1037
	preempt_disable();
1038 1039
	if (tsk->nr_dirtied)
		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
1040
	exit_rcu();
O
Oleg Nesterov 已提交
1041
	/* causes final put_task_struct in finish_task_switch(). */
1042
	tsk->state = TASK_DEAD;
1043
	tsk->flags |= PF_NOFREEZE;	/* tell freezer to ignore us */
L
Linus Torvalds 已提交
1044 1045 1046
	schedule();
	BUG();
	/* Avoid "noreturn function does return".  */
A
Alan Cox 已提交
1047 1048
	for (;;)
		cpu_relax();	/* For when BUG is null */
L
Linus Torvalds 已提交
1049 1050
}

1051 1052
EXPORT_SYMBOL_GPL(do_exit);

1053
void complete_and_exit(struct completion *comp, long code)
L
Linus Torvalds 已提交
1054 1055 1056
{
	if (comp)
		complete(comp);
O
Oleg Nesterov 已提交
1057

L
Linus Torvalds 已提交
1058 1059 1060 1061 1062
	do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

1063
SYSCALL_DEFINE1(exit, int, error_code)
L
Linus Torvalds 已提交
1064 1065 1066 1067 1068 1069 1070 1071
{
	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).
 */
1072
void
L
Linus Torvalds 已提交
1073 1074
do_group_exit(int exit_code)
{
1075 1076
	struct signal_struct *sig = current->signal;

L
Linus Torvalds 已提交
1077 1078
	BUG_ON(exit_code & 0x80); /* core dumps don't get here */

1079 1080
	if (signal_group_exit(sig))
		exit_code = sig->group_exit_code;
L
Linus Torvalds 已提交
1081 1082 1083
	else if (!thread_group_empty(current)) {
		struct sighand_struct *const sighand = current->sighand;
		spin_lock_irq(&sighand->siglock);
1084
		if (signal_group_exit(sig))
L
Linus Torvalds 已提交
1085 1086 1087 1088
			/* Another thread got here before we took the lock.  */
			exit_code = sig->group_exit_code;
		else {
			sig->group_exit_code = exit_code;
1089
			sig->flags = SIGNAL_GROUP_EXIT;
L
Linus Torvalds 已提交
1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103
			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.
 */
1104
SYSCALL_DEFINE1(exit_group, int, error_code)
L
Linus Torvalds 已提交
1105 1106
{
	do_group_exit((error_code & 0xff) << 8);
1107 1108
	/* NOTREACHED */
	return 0;
L
Linus Torvalds 已提交
1109 1110
}

1111 1112 1113
struct wait_opts {
	enum pid_type		wo_type;
	int			wo_flags;
1114
	struct pid		*wo_pid;
1115 1116 1117 1118 1119

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

1120
	wait_queue_t		child_wait;
1121 1122 1123
	int			notask_error;
};

1124 1125
static inline
struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
E
Eric W. Biederman 已提交
1126
{
1127 1128 1129
	if (type != PIDTYPE_PID)
		task = task->group_leader;
	return task->pids[type].pid;
E
Eric W. Biederman 已提交
1130 1131
}

1132
static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
L
Linus Torvalds 已提交
1133
{
1134 1135 1136
	return	wo->wo_type == PIDTYPE_MAX ||
		task_pid_type(p, wo->wo_type) == wo->wo_pid;
}
L
Linus Torvalds 已提交
1137

1138 1139 1140 1141
static int eligible_child(struct wait_opts *wo, struct task_struct *p)
{
	if (!eligible_pid(wo, p))
		return 0;
L
Linus Torvalds 已提交
1142 1143 1144 1145 1146
	/* 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.) */
1147 1148
	if (((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
	    && !(wo->wo_flags & __WALL))
L
Linus Torvalds 已提交
1149 1150
		return 0;

1151
	return 1;
L
Linus Torvalds 已提交
1152 1153
}

1154 1155
static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
				pid_t pid, uid_t uid, int why, int status)
L
Linus Torvalds 已提交
1156
{
1157 1158 1159
	struct siginfo __user *infop;
	int retval = wo->wo_rusage
		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1160

L
Linus Torvalds 已提交
1161
	put_task_struct(p);
1162
	infop = wo->wo_info;
1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176
	if (infop) {
		if (!retval)
			retval = put_user(SIGCHLD, &infop->si_signo);
		if (!retval)
			retval = put_user(0, &infop->si_errno);
		if (!retval)
			retval = put_user((short)why, &infop->si_code);
		if (!retval)
			retval = put_user(pid, &infop->si_pid);
		if (!retval)
			retval = put_user(uid, &infop->si_uid);
		if (!retval)
			retval = put_user(status, &infop->si_status);
	}
L
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1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187
	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 wait_opts *wo, struct task_struct *p)
L
Linus Torvalds 已提交
1189 1190
{
	unsigned long state;
1191
	int retval, status, traced;
1192
	pid_t pid = task_pid_vnr(p);
1193
	uid_t uid = __task_cred(p)->uid;
1194
	struct siginfo __user *infop;
L
Linus Torvalds 已提交
1195

1196
	if (!likely(wo->wo_flags & WEXITED))
R
Roland McGrath 已提交
1197 1198
		return 0;

1199
	if (unlikely(wo->wo_flags & WNOWAIT)) {
L
Linus Torvalds 已提交
1200
		int exit_code = p->exit_code;
1201
		int why;
L
Linus Torvalds 已提交
1202 1203 1204 1205 1206 1207 1208 1209 1210 1211

		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;
		}
1212
		return wait_noreap_copyout(wo, p, pid, uid, why, status);
L
Linus Torvalds 已提交
1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
	}

	/*
	 * 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;
	}

1225
	traced = ptrace_reparented(p);
1226 1227
	/*
	 * It can be ptraced but not reparented, check
O
Oleg Nesterov 已提交
1228
	 * thread_group_leader() to filter out sub-threads.
1229
	 */
O
Oleg Nesterov 已提交
1230
	if (likely(!traced) && thread_group_leader(p)) {
1231 1232
		struct signal_struct *psig;
		struct signal_struct *sig;
J
Jiri Pirko 已提交
1233
		unsigned long maxrss;
1234
		cputime_t tgutime, tgstime;
1235

L
Linus Torvalds 已提交
1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246
		/*
		 * 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
1247
		 * need to protect the access to parent->signal fields,
L
Linus Torvalds 已提交
1248 1249
		 * as other threads in the parent group can be right
		 * here reaping other children at the same time.
1250 1251 1252 1253
		 *
		 * We use thread_group_times() to get times for the thread
		 * group, which consolidates times for all threads in the
		 * group including the group leader.
L
Linus Torvalds 已提交
1254
		 */
1255
		thread_group_times(p, &tgutime, &tgstime);
1256 1257
		spin_lock_irq(&p->real_parent->sighand->siglock);
		psig = p->real_parent->signal;
1258
		sig = p->signal;
1259 1260 1261
		psig->cutime += tgutime + sig->cutime;
		psig->cstime += tgstime + sig->cstime;
		psig->cgtime += p->gtime + sig->gtime + sig->cgtime;
1262 1263 1264 1265 1266 1267 1268 1269
		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;
1270 1271 1272 1273 1274 1275
		psig->cinblock +=
			task_io_get_inblock(p) +
			sig->inblock + sig->cinblock;
		psig->coublock +=
			task_io_get_oublock(p) +
			sig->oublock + sig->coublock;
J
Jiri Pirko 已提交
1276 1277 1278
		maxrss = max(sig->maxrss, sig->cmaxrss);
		if (psig->cmaxrss < maxrss)
			psig->cmaxrss = maxrss;
1279 1280
		task_io_accounting_add(&psig->ioac, &p->ioac);
		task_io_accounting_add(&psig->ioac, &sig->ioac);
1281
		spin_unlock_irq(&p->real_parent->sighand->siglock);
L
Linus Torvalds 已提交
1282 1283 1284 1285 1286 1287 1288 1289
	}

	/*
	 * 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);

1290 1291
	retval = wo->wo_rusage
		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
L
Linus Torvalds 已提交
1292 1293
	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
		? p->signal->group_exit_code : p->exit_code;
1294 1295 1296 1297
	if (!retval && wo->wo_stat)
		retval = put_user(status, wo->wo_stat);

	infop = wo->wo_info;
L
Linus Torvalds 已提交
1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316
	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)
1317
		retval = put_user(pid, &infop->si_pid);
L
Linus Torvalds 已提交
1318
	if (!retval && infop)
1319
		retval = put_user(uid, &infop->si_uid);
1320
	if (!retval)
1321
		retval = pid;
1322 1323

	if (traced) {
L
Linus Torvalds 已提交
1324
		write_lock_irq(&tasklist_lock);
1325 1326 1327
		/* We dropped tasklist, ptracer could die and untrace */
		ptrace_unlink(p);
		/*
1328 1329
		 * If this is not a sub-thread, notify the parent.
		 * If parent wants a zombie, don't release it now.
1330
		 */
1331 1332 1333 1334
		if (thread_group_leader(p) &&
		    !do_notify_parent(p, p->exit_signal)) {
			p->exit_state = EXIT_ZOMBIE;
			p = NULL;
L
Linus Torvalds 已提交
1335 1336 1337 1338 1339
		}
		write_unlock_irq(&tasklist_lock);
	}
	if (p != NULL)
		release_task(p);
1340

L
Linus Torvalds 已提交
1341 1342 1343
	return retval;
}

1344 1345 1346
static int *task_stopped_code(struct task_struct *p, bool ptrace)
{
	if (ptrace) {
T
Tejun Heo 已提交
1347 1348
		if (task_is_stopped_or_traced(p) &&
		    !(p->jobctl & JOBCTL_LISTENING))
1349 1350 1351 1352 1353 1354 1355 1356
			return &p->exit_code;
	} else {
		if (p->signal->flags & SIGNAL_STOP_STOPPED)
			return &p->signal->group_exit_code;
	}
	return NULL;
}

1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373
/**
 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
 * @wo: wait options
 * @ptrace: is the wait for ptrace
 * @p: task to wait for
 *
 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
 *
 * CONTEXT:
 * read_lock(&tasklist_lock), which is released if return value is
 * non-zero.  Also, grabs and releases @p->sighand->siglock.
 *
 * RETURNS:
 * 0 if wait condition didn't exist and search for other wait conditions
 * should continue.  Non-zero return, -errno on failure and @p's pid on
 * success, implies that tasklist_lock is released and wait condition
 * search should terminate.
L
Linus Torvalds 已提交
1374
 */
1375 1376
static int wait_task_stopped(struct wait_opts *wo,
				int ptrace, struct task_struct *p)
L
Linus Torvalds 已提交
1377
{
1378
	struct siginfo __user *infop;
1379
	int retval, exit_code, *p_code, why;
1380
	uid_t uid = 0; /* unneeded, required by compiler */
1381
	pid_t pid;
L
Linus Torvalds 已提交
1382

1383 1384 1385
	/*
	 * Traditionally we see ptrace'd stopped tasks regardless of options.
	 */
1386
	if (!ptrace && !(wo->wo_flags & WUNTRACED))
R
Roland McGrath 已提交
1387 1388
		return 0;

1389 1390 1391
	if (!task_stopped_code(p, ptrace))
		return 0;

1392 1393 1394
	exit_code = 0;
	spin_lock_irq(&p->sighand->siglock);

1395 1396
	p_code = task_stopped_code(p, ptrace);
	if (unlikely(!p_code))
1397 1398
		goto unlock_sig;

1399
	exit_code = *p_code;
1400 1401 1402
	if (!exit_code)
		goto unlock_sig;

1403
	if (!unlikely(wo->wo_flags & WNOWAIT))
1404
		*p_code = 0;
1405

1406
	uid = task_uid(p);
1407 1408 1409
unlock_sig:
	spin_unlock_irq(&p->sighand->siglock);
	if (!exit_code)
L
Linus Torvalds 已提交
1410 1411 1412 1413 1414 1415 1416 1417 1418 1419
		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);
1420
	pid = task_pid_vnr(p);
R
Roland McGrath 已提交
1421
	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
L
Linus Torvalds 已提交
1422 1423
	read_unlock(&tasklist_lock);

1424 1425 1426 1427 1428 1429 1430
	if (unlikely(wo->wo_flags & WNOWAIT))
		return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);

	retval = wo->wo_rusage
		? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
	if (!retval && wo->wo_stat)
		retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
L
Linus Torvalds 已提交
1431

1432
	infop = wo->wo_info;
L
Linus Torvalds 已提交
1433 1434 1435 1436 1437
	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
1438
		retval = put_user((short)why, &infop->si_code);
L
Linus Torvalds 已提交
1439 1440 1441
	if (!retval && infop)
		retval = put_user(exit_code, &infop->si_status);
	if (!retval && infop)
1442
		retval = put_user(pid, &infop->si_pid);
L
Linus Torvalds 已提交
1443
	if (!retval && infop)
1444
		retval = put_user(uid, &infop->si_uid);
L
Linus Torvalds 已提交
1445
	if (!retval)
1446
		retval = pid;
L
Linus Torvalds 已提交
1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458
	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.
 */
1459
static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
L
Linus Torvalds 已提交
1460 1461 1462 1463 1464
{
	int retval;
	pid_t pid;
	uid_t uid;

1465
	if (!unlikely(wo->wo_flags & WCONTINUED))
R
Roland McGrath 已提交
1466 1467
		return 0;

L
Linus Torvalds 已提交
1468 1469 1470 1471 1472 1473 1474 1475 1476
	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;
	}
1477
	if (!unlikely(wo->wo_flags & WNOWAIT))
L
Linus Torvalds 已提交
1478
		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1479
	uid = task_uid(p);
L
Linus Torvalds 已提交
1480 1481
	spin_unlock_irq(&p->sighand->siglock);

1482
	pid = task_pid_vnr(p);
L
Linus Torvalds 已提交
1483 1484 1485
	get_task_struct(p);
	read_unlock(&tasklist_lock);

1486 1487 1488
	if (!wo->wo_info) {
		retval = wo->wo_rusage
			? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
L
Linus Torvalds 已提交
1489
		put_task_struct(p);
1490 1491
		if (!retval && wo->wo_stat)
			retval = put_user(0xffff, wo->wo_stat);
L
Linus Torvalds 已提交
1492
		if (!retval)
1493
			retval = pid;
L
Linus Torvalds 已提交
1494
	} else {
1495 1496
		retval = wait_noreap_copyout(wo, p, pid, uid,
					     CLD_CONTINUED, SIGCONT);
L
Linus Torvalds 已提交
1497 1498 1499 1500 1501 1502
		BUG_ON(retval == 0);
	}

	return retval;
}

R
Roland McGrath 已提交
1503 1504 1505
/*
 * Consider @p for a wait by @parent.
 *
1506
 * -ECHILD should be in ->notask_error before the first call.
R
Roland McGrath 已提交
1507 1508
 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
 * Returns zero if the search for a child should continue;
1509
 * then ->notask_error is 0 if @p is an eligible child,
1510
 * or another error from security_task_wait(), or still -ECHILD.
R
Roland McGrath 已提交
1511
 */
1512 1513
static int wait_consider_task(struct wait_opts *wo, int ptrace,
				struct task_struct *p)
R
Roland McGrath 已提交
1514
{
1515
	int ret = eligible_child(wo, p);
1516
	if (!ret)
R
Roland McGrath 已提交
1517 1518
		return ret;

1519
	ret = security_task_wait(p);
1520 1521 1522 1523 1524 1525 1526 1527
	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.
		 */
1528 1529
		if (wo->notask_error)
			wo->notask_error = ret;
1530
		return 0;
1531 1532
	}

1533
	/* dead body doesn't have much to contribute */
1534 1535 1536 1537 1538 1539 1540
	if (unlikely(p->exit_state == EXIT_DEAD)) {
		/*
		 * But do not ignore this task until the tracer does
		 * wait_task_zombie()->do_notify_parent().
		 */
		if (likely(!ptrace) && unlikely(ptrace_reparented(p)))
			wo->notask_error = 0;
1541
		return 0;
1542
	}
1543

1544 1545
	/* slay zombie? */
	if (p->exit_state == EXIT_ZOMBIE) {
R
Roland McGrath 已提交
1546
		/*
1547 1548 1549
		 * A zombie ptracee is only visible to its ptracer.
		 * Notification and reaping will be cascaded to the real
		 * parent when the ptracer detaches.
R
Roland McGrath 已提交
1550
		 */
T
Tejun Heo 已提交
1551
		if (likely(!ptrace) && unlikely(p->ptrace)) {
1552 1553 1554 1555
			/* it will become visible, clear notask_error */
			wo->notask_error = 0;
			return 0;
		}
R
Roland McGrath 已提交
1556

1557 1558 1559
		/* we don't reap group leaders with subthreads */
		if (!delay_group_leader(p))
			return wait_task_zombie(wo, p);
R
Roland McGrath 已提交
1560

R
Roland McGrath 已提交
1561
		/*
1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583
		 * Allow access to stopped/continued state via zombie by
		 * falling through.  Clearing of notask_error is complex.
		 *
		 * When !@ptrace:
		 *
		 * If WEXITED is set, notask_error should naturally be
		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
		 * so, if there are live subthreads, there are events to
		 * wait for.  If all subthreads are dead, it's still safe
		 * to clear - this function will be called again in finite
		 * amount time once all the subthreads are released and
		 * will then return without clearing.
		 *
		 * When @ptrace:
		 *
		 * Stopped state is per-task and thus can't change once the
		 * target task dies.  Only continued and exited can happen.
		 * Clear notask_error if WCONTINUED | WEXITED.
		 */
		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
			wo->notask_error = 0;
	} else {
1584 1585 1586 1587 1588 1589 1590 1591 1592 1593
		/*
		 * If @p is ptraced by a task in its real parent's group,
		 * hide group stop/continued state when looking at @p as
		 * the real parent; otherwise, a single stop can be
		 * reported twice as group and ptrace stops.
		 *
		 * If a ptracer wants to distinguish the two events for its
		 * own children, it should create a separate process which
		 * takes the role of real parent.
		 */
1594
		if (likely(!ptrace) && p->ptrace && !ptrace_reparented(p))
1595 1596
			return 0;

1597 1598 1599
		/*
		 * @p is alive and it's gonna stop, continue or exit, so
		 * there always is something to wait for.
R
Roland McGrath 已提交
1600
		 */
1601
		wo->notask_error = 0;
R
Roland McGrath 已提交
1602 1603
	}

R
Roland McGrath 已提交
1604
	/*
1605 1606
	 * Wait for stopped.  Depending on @ptrace, different stopped state
	 * is used and the two don't interact with each other.
R
Roland McGrath 已提交
1607
	 */
1608 1609 1610
	ret = wait_task_stopped(wo, ptrace, p);
	if (ret)
		return ret;
R
Roland McGrath 已提交
1611 1612

	/*
1613 1614 1615
	 * Wait for continued.  There's only one continued state and the
	 * ptracer can consume it which can confuse the real parent.  Don't
	 * use WCONTINUED from ptracer.  You don't need or want it.
R
Roland McGrath 已提交
1616
	 */
1617
	return wait_task_continued(wo, p);
R
Roland McGrath 已提交
1618 1619 1620 1621 1622
}

/*
 * Do the work of do_wait() for one thread in the group, @tsk.
 *
1623
 * -ECHILD should be in ->notask_error before the first call.
R
Roland McGrath 已提交
1624 1625
 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
 * Returns zero if the search for a child should continue; then
1626
 * ->notask_error is 0 if there were any eligible children,
1627
 * or another error from security_task_wait(), or still -ECHILD.
R
Roland McGrath 已提交
1628
 */
1629
static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
R
Roland McGrath 已提交
1630 1631 1632 1633
{
	struct task_struct *p;

	list_for_each_entry(p, &tsk->children, sibling) {
1634 1635 1636
		int ret = wait_consider_task(wo, 0, p);
		if (ret)
			return ret;
R
Roland McGrath 已提交
1637 1638 1639 1640 1641
	}

	return 0;
}

1642
static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
R
Roland McGrath 已提交
1643 1644 1645
{
	struct task_struct *p;

R
Roland McGrath 已提交
1646
	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1647
		int ret = wait_consider_task(wo, 1, p);
R
Roland McGrath 已提交
1648
		if (ret)
R
Roland McGrath 已提交
1649 1650 1651 1652 1653 1654
			return ret;
	}

	return 0;
}

1655 1656 1657 1658 1659 1660 1661
static int child_wait_callback(wait_queue_t *wait, unsigned mode,
				int sync, void *key)
{
	struct wait_opts *wo = container_of(wait, struct wait_opts,
						child_wait);
	struct task_struct *p = key;

1662
	if (!eligible_pid(wo, p))
1663 1664
		return 0;

1665 1666 1667
	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
		return 0;

1668 1669 1670
	return default_wake_function(wait, mode, sync, key);
}

1671 1672
void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
{
1673 1674
	__wake_up_sync_key(&parent->signal->wait_chldexit,
				TASK_INTERRUPTIBLE, 1, p);
1675 1676
}

1677
static long do_wait(struct wait_opts *wo)
L
Linus Torvalds 已提交
1678 1679
{
	struct task_struct *tsk;
R
Roland McGrath 已提交
1680
	int retval;
L
Linus Torvalds 已提交
1681

1682
	trace_sched_process_wait(wo->wo_pid);
1683

1684 1685 1686
	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
	wo->child_wait.private = current;
	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
L
Linus Torvalds 已提交
1687
repeat:
R
Roland McGrath 已提交
1688 1689
	/*
	 * If there is nothing that can match our critiera just get out.
1690 1691 1692
	 * We will clear ->notask_error to zero if we see any child that
	 * might later match our criteria, even if we are not able to reap
	 * it yet.
R
Roland McGrath 已提交
1693
	 */
1694
	wo->notask_error = -ECHILD;
1695 1696
	if ((wo->wo_type < PIDTYPE_MAX) &&
	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1697
		goto notask;
E
Eric W. Biederman 已提交
1698

1699
	set_current_state(TASK_INTERRUPTIBLE);
L
Linus Torvalds 已提交
1700 1701 1702
	read_lock(&tasklist_lock);
	tsk = current;
	do {
1703 1704 1705
		retval = do_wait_thread(wo, tsk);
		if (retval)
			goto end;
1706

1707 1708
		retval = ptrace_do_wait(wo, tsk);
		if (retval)
R
Roland McGrath 已提交
1709 1710
			goto end;

1711
		if (wo->wo_flags & __WNOTHREAD)
L
Linus Torvalds 已提交
1712
			break;
1713
	} while_each_thread(current, tsk);
L
Linus Torvalds 已提交
1714
	read_unlock(&tasklist_lock);
O
Oleg Nesterov 已提交
1715

1716
notask:
1717 1718
	retval = wo->notask_error;
	if (!retval && !(wo->wo_flags & WNOHANG)) {
L
Linus Torvalds 已提交
1719
		retval = -ERESTARTSYS;
R
Roland McGrath 已提交
1720 1721 1722 1723
		if (!signal_pending(current)) {
			schedule();
			goto repeat;
		}
L
Linus Torvalds 已提交
1724 1725
	}
end:
1726
	__set_current_state(TASK_RUNNING);
1727
	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
L
Linus Torvalds 已提交
1728 1729 1730
	return retval;
}

1731 1732
SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
		infop, int, options, struct rusage __user *, ru)
L
Linus Torvalds 已提交
1733
{
1734
	struct wait_opts wo;
E
Eric W. Biederman 已提交
1735 1736
	struct pid *pid = NULL;
	enum pid_type type;
L
Linus Torvalds 已提交
1737 1738 1739 1740 1741 1742 1743 1744 1745
	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
1746
		type = PIDTYPE_MAX;
L
Linus Torvalds 已提交
1747 1748
		break;
	case P_PID:
E
Eric W. Biederman 已提交
1749 1750
		type = PIDTYPE_PID;
		if (upid <= 0)
L
Linus Torvalds 已提交
1751 1752 1753
			return -EINVAL;
		break;
	case P_PGID:
E
Eric W. Biederman 已提交
1754 1755
		type = PIDTYPE_PGID;
		if (upid <= 0)
L
Linus Torvalds 已提交
1756 1757 1758 1759 1760 1761
			return -EINVAL;
		break;
	default:
		return -EINVAL;
	}

E
Eric W. Biederman 已提交
1762 1763
	if (type < PIDTYPE_MAX)
		pid = find_get_pid(upid);
1764 1765 1766 1767 1768 1769 1770 1771

	wo.wo_type	= type;
	wo.wo_pid	= pid;
	wo.wo_flags	= options;
	wo.wo_info	= infop;
	wo.wo_stat	= NULL;
	wo.wo_rusage	= ru;
	ret = do_wait(&wo);
1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794

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

E
Eric W. Biederman 已提交
1795
	put_pid(pid);
L
Linus Torvalds 已提交
1796 1797

	/* avoid REGPARM breakage on x86: */
1798
	asmlinkage_protect(5, ret, which, upid, infop, options, ru);
L
Linus Torvalds 已提交
1799 1800 1801
	return ret;
}

1802 1803
SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
		int, options, struct rusage __user *, ru)
L
Linus Torvalds 已提交
1804
{
1805
	struct wait_opts wo;
E
Eric W. Biederman 已提交
1806 1807
	struct pid *pid = NULL;
	enum pid_type type;
L
Linus Torvalds 已提交
1808 1809 1810 1811 1812
	long ret;

	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
			__WNOTHREAD|__WCLONE|__WALL))
		return -EINVAL;
E
Eric W. Biederman 已提交
1813 1814 1815 1816 1817 1818 1819 1820

	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;
1821
		pid = get_task_pid(current, PIDTYPE_PGID);
E
Eric W. Biederman 已提交
1822 1823 1824 1825 1826
	} else /* upid > 0 */ {
		type = PIDTYPE_PID;
		pid = find_get_pid(upid);
	}

1827 1828 1829 1830 1831 1832 1833
	wo.wo_type	= type;
	wo.wo_pid	= pid;
	wo.wo_flags	= options | WEXITED;
	wo.wo_info	= NULL;
	wo.wo_stat	= stat_addr;
	wo.wo_rusage	= ru;
	ret = do_wait(&wo);
E
Eric W. Biederman 已提交
1834
	put_pid(pid);
L
Linus Torvalds 已提交
1835 1836

	/* avoid REGPARM breakage on x86: */
1837
	asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
L
Linus Torvalds 已提交
1838 1839 1840 1841 1842 1843 1844 1845 1846
	return ret;
}

#ifdef __ARCH_WANT_SYS_WAITPID

/*
 * sys_waitpid() remains for compatibility. waitpid() should be
 * implemented by calling sys_wait4() from libc.a.
 */
1847
SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
L
Linus Torvalds 已提交
1848 1849 1850 1851 1852
{
	return sys_wait4(pid, stat_addr, options, NULL);
}

#endif