exit.c 43.4 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/mnt_namespace.h>
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#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
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#include <linux/tsacct_kern.h>
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#include <linux/file.h>
#include <linux/binfmts.h>
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#include <linux/nsproxy.h>
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#include <linux/pid_namespace.h>
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#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
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#include <linux/kthread.h>
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#include <linux/mempolicy.h>
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#include <linux/taskstats_kern.h>
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#include <linux/delayacct.h>
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#include <linux/freezer.h>
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#include <linux/cgroup.h>
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#include <linux/syscalls.h>
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#include <linux/signal.h>
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#include <linux/posix-timers.h>
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#include <linux/cn_proc.h>
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#include <linux/mutex.h>
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#include <linux/futex.h>
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#include <linux/compat.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/audit.h> /* for audit_free() */
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#include <linux/resource.h>
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#include <linux/blkdev.h>
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#include <linux/task_io_accounting_ops.h>
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#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

extern void sem_exit (void);

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static void exit_mm(struct task_struct * tsk);

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

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

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

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

	posix_cpu_timers_exit(tsk);
	if (atomic_dec_and_test(&sig->count))
		posix_cpu_timers_exit_group(tsk);
	else {
		/*
		 * If there is any task waiting for the group exit
		 * then notify it:
		 */
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		if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
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			wake_up_process(sig->group_exit_task);
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		if (tsk == sig->curr_target)
			sig->curr_target = next_thread(tsk);
		/*
		 * Accumulate here the counters for all threads but the
		 * group leader as they die, so they can be added into
		 * the process-wide totals when those are taken.
		 * The group leader stays around as a zombie as long
		 * as there are other threads.  When it gets reaped,
		 * the exit.c code will add its counts into these totals.
		 * We won't ever get here for the group leader, since it
		 * will have been the last reference on the signal_struct.
		 */
		sig->utime = cputime_add(sig->utime, tsk->utime);
		sig->stime = cputime_add(sig->stime, tsk->stime);
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		sig->gtime = cputime_add(sig->gtime, tsk->gtime);
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		sig->min_flt += tsk->min_flt;
		sig->maj_flt += tsk->maj_flt;
		sig->nvcsw += tsk->nvcsw;
		sig->nivcsw += tsk->nivcsw;
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		sig->inblock += task_io_get_inblock(tsk);
		sig->oublock += task_io_get_oublock(tsk);
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		sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
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		sig = NULL; /* Marker for below. */
	}

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	__unhash_process(tsk);

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

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

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

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void release_task(struct task_struct * p)
{
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	struct task_struct *leader;
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	int zap_leader;
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repeat:
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	atomic_dec(&p->user->processes);
	write_lock_irq(&tasklist_lock);
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	ptrace_unlink(p);
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	BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
	__exit_signal(p);
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	/*
	 * If we are the last non-leader member of the thread
	 * group, and the leader is zombie, then notify the
	 * group leader's parent process. (if it wants notification.)
	 */
	zap_leader = 0;
	leader = p->group_leader;
	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
		BUG_ON(leader->exit_signal == -1);
		do_notify_parent(leader, leader->exit_signal);
		/*
		 * If we were the last child thread and the leader has
		 * exited already, and the leader's parent ignores SIGCHLD,
		 * then we are the one who should release the leader.
		 *
		 * do_notify_parent() will have marked it self-reaping in
		 * that case.
		 */
		zap_leader = (leader->exit_signal == -1);
	}

	write_unlock_irq(&tasklist_lock);
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	proc_flush_task(p);
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	release_thread(p);
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	call_rcu(&p->rcu, delayed_put_task_struct);
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	p = leader;
	if (unlikely(zap_leader))
		goto repeat;
}

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

/*
 * Determine if a process group is "orphaned", according to the POSIX
 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 * by terminal-generated stop signals.  Newly orphaned process groups are
 * to receive a SIGHUP and a SIGCONT.
 *
 * "I ask you, have you ever known what it is to be an orphan?"
 */
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static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
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{
	struct task_struct *p;
	int ret = 1;

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

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int is_current_pgrp_orphaned(void)
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{
	int retval;

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

	return retval;
}

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

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	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
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		if (p->state != TASK_STOPPED)
			continue;
		retval = 1;
		break;
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	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
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	return retval;
}

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

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

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

void __set_special_pids(pid_t session, pid_t pgrp)
{
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	struct task_struct *curr = current->group_leader;
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	if (process_session(curr) != session) {
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		detach_pid(curr, PIDTYPE_SID);
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		set_signal_session(curr->signal, session);
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		attach_pid(curr, PIDTYPE_SID, find_pid(session));
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	}
	if (process_group(curr) != pgrp) {
		detach_pid(curr, PIDTYPE_PGID);
		curr->signal->pgrp = pgrp;
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		attach_pid(curr, PIDTYPE_PGID, find_pid(pgrp));
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	}
}

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

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

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

EXPORT_SYMBOL(allow_signal);

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

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

EXPORT_SYMBOL(disallow_signal);

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

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

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

	/*
	 * If we were started as result of loading a module, close all of the
	 * user space pages.  We don't need them, and if we didn't close them
	 * they would be locked into memory.
	 */
	exit_mm(current);
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	/*
	 * We don't want to have TIF_FREEZE set if the system-wide hibernation
	 * or suspend transition begins right now.
	 */
	current->flags |= PF_NOFREEZE;
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	set_special_pids(1, 1);
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	proc_clear_tty(current);
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	/* Block and flush all signals */
	sigfillset(&blocked);
	sigprocmask(SIG_BLOCK, &blocked, NULL);
	flush_signals(current);

	/* Become as one with the init task */

	exit_fs(current);	/* current->fs->count--; */
	fs = init_task.fs;
	current->fs = fs;
	atomic_inc(&fs->count);
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	exit_task_namespaces(current);
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	current->nsproxy = init_task.nsproxy;
	get_task_namespaces(current);

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 	exit_files(current);
	current->files = init_task.files;
	atomic_inc(&current->files->count);

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	reparent_to_kthreadd();
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}

EXPORT_SYMBOL(daemonize);

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

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

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

	return files;
}

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

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

EXPORT_SYMBOL(put_files_struct);

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

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

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

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

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

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

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

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

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

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

EXPORT_SYMBOL_GPL(exit_fs);

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

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

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

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

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	/* Move the child from its dying parent to the new one.  */
	if (unlikely(traced)) {
		/* Preserve ptrace links if someone else is tracing this child.  */
		list_del_init(&p->ptrace_list);
		if (p->parent != p->real_parent)
			list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
	} else {
		/* If this child is being traced, then we're the one tracing it
		 * anyway, so let go of it.
		 */
		p->ptrace = 0;
612
		remove_parent(p);
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		p->parent = p->real_parent;
614
		add_parent(p);
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616
		if (p->state == TASK_TRACED) {
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			/*
			 * If it was at a trace stop, turn it into
			 * a normal stop since it's no longer being
			 * traced.
			 */
			ptrace_untrace(p);
		}
	}

626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642
	/* If this is a threaded reparent there is no need to
	 * notify anyone anything has happened.
	 */
	if (p->real_parent->group_leader == father->group_leader)
		return;

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

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

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	/*
	 * process group orphan check
	 * Case ii: Our child is in a different pgrp
	 * than we are, and it was the only connection
	 * outside, so the child pgrp is now orphaned.
	 */
649 650 651
	if ((task_pgrp(p) != task_pgrp(father)) &&
	    (task_session(p) == task_session(father))) {
		struct pid *pgrp = task_pgrp(p);
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653 654
		if (will_become_orphaned_pgrp(pgrp, NULL) &&
		    has_stopped_jobs(pgrp)) {
655 656
			__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
			__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
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		}
	}
}

/*
 * When we die, we re-parent all our children.
 * Try to give them to another thread in our thread
 * group, and if no such member exists, give it to
665 666
 * the child reaper process (ie "init") in our pid
 * space.
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 */
668 669
static void
forget_original_parent(struct task_struct *father, struct list_head *to_release)
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{
	struct task_struct *p, *reaper = father;
	struct list_head *_p, *_n;

	do {
		reaper = next_thread(reaper);
		if (reaper == father) {
677
			reaper = child_reaper(father);
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			break;
		}
	} while (reaper->exit_state);

	/*
	 * There are only two places where our children can be:
	 *
	 * - in our child list
	 * - in our ptraced child list
	 *
	 * Search them and reparent children.
	 */
	list_for_each_safe(_p, _n, &father->children) {
		int ptrace;
692
		p = list_entry(_p, struct task_struct, sibling);
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		ptrace = p->ptrace;

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

		if (father == p->real_parent) {
			/* reparent with a reaper, real father it's us */
701
			p->real_parent = reaper;
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			reparent_thread(p, father, 0);
		} else {
			/* reparent ptraced task to its real parent */
			__ptrace_unlink (p);
			if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
			    thread_group_empty(p))
				do_notify_parent(p, p->exit_signal);
		}

		/*
		 * if the ptraced child is a zombie with exit_signal == -1
		 * we must collect it before we exit, or it will remain
		 * zombie forever since we prevented it from self-reap itself
		 * while it was being traced by us, to be able to see it in wait4.
		 */
		if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
			list_add(&p->ptrace_list, to_release);
	}
	list_for_each_safe(_p, _n, &father->ptrace_children) {
721
		p = list_entry(_p, struct task_struct, ptrace_list);
722
		p->real_parent = reaper;
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		reparent_thread(p, father, 1);
	}
}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
static void exit_notify(struct task_struct *tsk)
{
	int state;
	struct task_struct *t;
	struct list_head ptrace_dead, *_p, *_n;
736
	struct pid *pgrp;
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	if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
	    && !thread_group_empty(tsk)) {
		/*
		 * This occurs when there was a race between our exit
		 * syscall and a group signal choosing us as the one to
		 * wake up.  It could be that we are the only thread
		 * alerted to check for pending signals, but another thread
		 * should be woken now to take the signal since we will not.
		 * Now we'll wake all the threads in the group just to make
		 * sure someone gets all the pending signals.
		 */
		spin_lock_irq(&tsk->sighand->siglock);
		for (t = next_thread(tsk); t != tsk; t = next_thread(t))
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Roland McGrath 已提交
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			if (!signal_pending(t) && !(t->flags & PF_EXITING))
				recalc_sigpending_and_wake(t);
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		spin_unlock_irq(&tsk->sighand->siglock);
	}

	write_lock_irq(&tasklist_lock);

	/*
	 * 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)
	 */

	INIT_LIST_HEAD(&ptrace_dead);
	forget_original_parent(tsk, &ptrace_dead);
	BUG_ON(!list_empty(&tsk->children));
	BUG_ON(!list_empty(&tsk->ptrace_children));

	/*
	 * Check to see if any process groups have become orphaned
	 * as a result of our exiting, and if they have any stopped
	 * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
	 *
	 * Case i: Our father is in a different pgrp than we are
	 * and we were the only connection outside, so our pgrp
	 * is about to become orphaned.
	 */
	t = tsk->real_parent;
782

783 784
	pgrp = task_pgrp(tsk);
	if ((task_pgrp(t) != pgrp) &&
785
	    (task_session(t) == task_session(tsk)) &&
786 787 788 789
	    will_become_orphaned_pgrp(pgrp, tsk) &&
	    has_stopped_jobs(pgrp)) {
		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
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	}

792
	/* Let father know we died
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	 *
	 * Thread signals are configurable, but you aren't going to use
	 * that to send signals to arbitary processes. 
	 * That stops right now.
	 *
	 * If the parent exec id doesn't match the exec id we saved
	 * when we started then we know the parent has changed security
	 * domain.
	 *
	 * If our self_exec id doesn't match our parent_exec_id then
	 * we have changed execution domain as these two values started
	 * the same after a fork.
	 */
	if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
	    ( tsk->parent_exec_id != t->self_exec_id  ||
	      tsk->self_exec_id != tsk->parent_exec_id)
	    && !capable(CAP_KILL))
		tsk->exit_signal = SIGCHLD;


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

	state = EXIT_ZOMBIE;
825
	if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
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		state = EXIT_DEAD;
	tsk->exit_state = state;

829 830 831 832 833
	if (thread_group_leader(tsk) &&
	    tsk->signal->notify_count < 0 &&
	    tsk->signal->group_exit_task)
		wake_up_process(tsk->signal->group_exit_task);

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	write_unlock_irq(&tasklist_lock);

	list_for_each_safe(_p, _n, &ptrace_dead) {
		list_del_init(_p);
838
		t = list_entry(_p, struct task_struct, ptrace_list);
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		release_task(t);
	}

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

847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874
#ifdef CONFIG_DEBUG_STACK_USAGE
static void check_stack_usage(void)
{
	static DEFINE_SPINLOCK(low_water_lock);
	static int lowest_to_date = THREAD_SIZE;
	unsigned long *n = end_of_stack(current);
	unsigned long free;

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

	if (free >= lowest_to_date)
		return;

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

875 876 877 878 879 880 881 882
static inline void exit_child_reaper(struct task_struct *tsk)
{
	if (likely(tsk->group_leader != child_reaper(tsk)))
		return;

	panic("Attempted to kill init!");
}

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

	profile_task_exit(tsk);

890 891
	WARN_ON(atomic_read(&tsk->fs_excl));

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

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

902 903 904 905 906 907 908
	/*
	 * 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");
909 910 911 912 913 914 915 916 917 918
		/*
		 * 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;
919 920
		if (tsk->io_context)
			exit_io_context();
921 922 923 924
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule();
	}

925
	tsk->flags |= PF_EXITING;
926 927 928 929
	/*
	 * tsk->flags are checked in the futex code to protect against
	 * an exiting task cleaning up the robust pi futexes.
	 */
930 931
	smp_mb();
	spin_unlock_wait(&tsk->pi_lock);
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	if (unlikely(in_atomic()))
		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
				current->comm, current->pid,
				preempt_count());

	acct_update_integrals(tsk);
939 940 941 942
	if (tsk->mm) {
		update_hiwater_rss(tsk->mm);
		update_hiwater_vm(tsk->mm);
	}
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943
	group_dead = atomic_dec_and_test(&tsk->signal->live);
944
	if (group_dead) {
945
		exit_child_reaper(tsk);
946
		hrtimer_cancel(&tsk->signal->real_timer);
947
		exit_itimers(tsk->signal);
948
	}
949
	acct_collect(code, group_dead);
950
#ifdef CONFIG_FUTEX
951 952
	if (unlikely(tsk->robust_list))
		exit_robust_list(tsk);
953
#ifdef CONFIG_COMPAT
954 955
	if (unlikely(tsk->compat_robust_list))
		compat_exit_robust_list(tsk);
956
#endif
957
#endif
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Miloslav Trmac 已提交
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	if (group_dead)
		tty_audit_exit();
960 961
	if (unlikely(tsk->audit_context))
		audit_free(tsk);
962

963
	tsk->exit_code = code;
964
	taskstats_exit(tsk, group_dead);
965

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966 967
	exit_mm(tsk);

968
	if (group_dead)
969
		acct_process();
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	exit_sem(tsk);
	__exit_files(tsk);
	__exit_fs(tsk);
973
	check_stack_usage();
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	exit_thread();
975
	cgroup_exit(tsk, 1);
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	exit_keys(tsk);

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

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	module_put(task_thread_info(tsk)->exec_domain->module);
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982 983 984
	if (tsk->binfmt)
		module_put(tsk->binfmt->module);

M
Matt Helsley 已提交
985
	proc_exit_connector(tsk);
986
	exit_task_namespaces(tsk);
987
	exit_notify(tsk);
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#ifdef CONFIG_NUMA
	mpol_free(tsk->mempolicy);
	tsk->mempolicy = NULL;
#endif
992
#ifdef CONFIG_FUTEX
993 994 995 996 997 998 999 1000
	/*
	 * 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);
1001
#endif
1002
	/*
1003
	 * Make sure we are holding no locks:
1004
	 */
1005
	debug_check_no_locks_held(tsk);
1006 1007 1008 1009 1010 1011
	/*
	 * 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;
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1013 1014 1015
	if (tsk->io_context)
		exit_io_context();

1016 1017 1018
	if (tsk->splice_pipe)
		__free_pipe_info(tsk->splice_pipe);

C
Coywolf Qi Hunt 已提交
1019
	preempt_disable();
O
Oleg Nesterov 已提交
1020
	/* causes final put_task_struct in finish_task_switch(). */
1021
	tsk->state = TASK_DEAD;
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Coywolf Qi Hunt 已提交
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1023 1024 1025
	schedule();
	BUG();
	/* Avoid "noreturn function does return".  */
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Alan Cox 已提交
1026 1027
	for (;;)
		cpu_relax();	/* For when BUG is null */
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1028 1029
}

1030 1031
EXPORT_SYMBOL_GPL(do_exit);

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NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
	if (comp)
		complete(comp);
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Oleg Nesterov 已提交
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	do_exit(code);
}

EXPORT_SYMBOL(complete_and_exit);

asmlinkage long sys_exit(int error_code)
{
	do_exit((error_code&0xff)<<8);
}

/*
 * Take down every thread in the group.  This is called by fatal signals
 * as well as by sys_exit_group (below).
 */
NORET_TYPE void
do_group_exit(int exit_code)
{
	BUG_ON(exit_code & 0x80); /* core dumps don't get here */

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

	do_exit(exit_code);
	/* NOTREACHED */
}

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

1086
static int eligible_child(pid_t pid, int options, struct task_struct *p)
L
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{
1088 1089
	int err;

L
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	if (pid > 0) {
		if (p->pid != pid)
			return 0;
	} else if (!pid) {
		if (process_group(p) != process_group(current))
			return 0;
	} else if (pid != -1) {
		if (process_group(p) != -pid)
			return 0;
	}

	/*
	 * Do not consider detached threads that are
	 * not ptraced:
	 */
	if (p->exit_signal == -1 && !p->ptrace)
		return 0;

	/* Wait for all children (clone and not) if __WALL is set;
	 * otherwise, wait for clone children *only* if __WCLONE is
	 * set; otherwise, wait for non-clone children *only*.  (Note:
	 * A "clone" child here is one that reports to its parent
	 * using a signal other than SIGCHLD.) */
	if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
	    && !(options & __WALL))
		return 0;
	/*
	 * Do not consider thread group leaders that are
	 * in a non-empty thread group:
	 */
1120
	if (delay_group_leader(p))
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		return 2;

1123 1124 1125
	err = security_task_wait(p);
	if (err)
		return err;
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	return 1;
}

1130
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
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			       int why, int status,
			       struct siginfo __user *infop,
			       struct rusage __user *rusagep)
{
	int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
1136

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	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.
 */
1161
static int wait_task_zombie(struct task_struct *p, int noreap,
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			    struct siginfo __user *infop,
			    int __user *stat_addr, struct rusage __user *ru)
{
	unsigned long state;
1166
	int retval, status, traced;
L
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	if (unlikely(noreap)) {
		pid_t pid = p->pid;
		uid_t uid = p->uid;
		int exit_code = p->exit_code;
		int why, status;

		if (unlikely(p->exit_state != EXIT_ZOMBIE))
			return 0;
		if (unlikely(p->exit_signal == -1 && p->ptrace == 0))
			return 0;
		get_task_struct(p);
		read_unlock(&tasklist_lock);
		if ((exit_code & 0x7f) == 0) {
			why = CLD_EXITED;
			status = exit_code >> 8;
		} else {
			why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
			status = exit_code & 0x7f;
		}
		return wait_noreap_copyout(p, pid, uid, why,
					   status, infop, ru);
	}

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

1201 1202 1203 1204
	/* traced means p->ptrace, but not vice versa */
	traced = (p->real_parent != p->parent);

	if (likely(!traced)) {
1205 1206 1207
		struct signal_struct *psig;
		struct signal_struct *sig;

L
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		/*
		 * The resource counters for the group leader are in its
		 * own task_struct.  Those for dead threads in the group
		 * are in its signal_struct, as are those for the child
		 * processes it has previously reaped.  All these
		 * accumulate in the parent's signal_struct c* fields.
		 *
		 * We don't bother to take a lock here to protect these
		 * p->signal fields, because they are only touched by
		 * __exit_signal, which runs with tasklist_lock
		 * write-locked anyway, and so is excluded here.  We do
		 * need to protect the access to p->parent->signal fields,
		 * as other threads in the parent group can be right
		 * here reaping other children at the same time.
		 */
		spin_lock_irq(&p->parent->sighand->siglock);
1224 1225 1226 1227
		psig = p->parent->signal;
		sig = p->signal;
		psig->cutime =
			cputime_add(psig->cutime,
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			cputime_add(p->utime,
1229 1230 1231 1232
			cputime_add(sig->utime,
				    sig->cutime)));
		psig->cstime =
			cputime_add(psig->cstime,
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			cputime_add(p->stime,
1234 1235
			cputime_add(sig->stime,
				    sig->cstime)));
1236 1237 1238 1239 1240
		psig->cgtime =
			cputime_add(psig->cgtime,
			cputime_add(p->gtime,
			cputime_add(sig->gtime,
				    sig->cgtime)));
1241 1242 1243 1244 1245 1246 1247 1248
		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;
1249 1250 1251 1252 1253 1254
		psig->cinblock +=
			task_io_get_inblock(p) +
			sig->inblock + sig->cinblock;
		psig->coublock +=
			task_io_get_oublock(p) +
			sig->oublock + sig->coublock;
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		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)
		retval = put_user(p->pid, &infop->si_pid);
	if (!retval && infop)
		retval = put_user(p->uid, &infop->si_uid);
1291 1292 1293 1294
	if (!retval)
		retval = p->pid;

	if (traced) {
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		write_lock_irq(&tasklist_lock);
1296 1297 1298 1299 1300 1301 1302 1303 1304
		/* We dropped tasklist, ptracer could die and untrace */
		ptrace_unlink(p);
		/*
		 * If this is not a detached task, notify the parent.
		 * If it's still not detached after that, don't release
		 * it now.
		 */
		if (p->exit_signal != -1) {
			do_notify_parent(p, p->exit_signal);
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			if (p->exit_signal != -1) {
1306 1307
				p->exit_state = EXIT_ZOMBIE;
				p = NULL;
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			}
		}
		write_unlock_irq(&tasklist_lock);
	}
	if (p != NULL)
		release_task(p);
1314

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	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.
 */
1324 1325
static int wait_task_stopped(struct task_struct *p, int delayed_group_leader,
			     int noreap, struct siginfo __user *infop,
L
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			     int __user *stat_addr, struct rusage __user *ru)
{
	int retval, exit_code;

	if (!p->exit_code)
		return 0;
	if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
1333
	    p->signal->group_stop_count > 0)
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		/*
		 * A group stop is in progress and this is the group leader.
		 * We won't report until all threads have stopped.
		 */
		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);
	read_unlock(&tasklist_lock);

	if (unlikely(noreap)) {
		pid_t pid = p->pid;
		uid_t uid = p->uid;
		int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;

		exit_code = p->exit_code;
		if (unlikely(!exit_code) ||
1357
		    unlikely(p->state & TASK_TRACED))
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			goto bail_ref;
		return wait_noreap_copyout(p, pid, uid,
					   why, (exit_code << 8) | 0x7f,
					   infop, ru);
	}

	write_lock_irq(&tasklist_lock);

	/*
	 * This uses xchg to be atomic with the thread resuming and setting
	 * it.  It must also be done with the write lock held to prevent a
	 * race with the EXIT_ZOMBIE case.
	 */
	exit_code = xchg(&p->exit_code, 0);
	if (unlikely(p->exit_state)) {
		/*
		 * The task resumed and then died.  Let the next iteration
		 * catch it in EXIT_ZOMBIE.  Note that exit_code might
		 * already be zero here if it resumed and did _exit(0).
		 * The task itself is dead and won't touch exit_code again;
		 * other processors in this function are locked out.
		 */
		p->exit_code = exit_code;
		exit_code = 0;
	}
	if (unlikely(exit_code == 0)) {
		/*
		 * Another thread in this function got to it first, or it
		 * resumed, or it resumed and then died.
		 */
		write_unlock_irq(&tasklist_lock);
bail_ref:
		put_task_struct(p);
		/*
		 * We are returning to the wait loop without having successfully
		 * removed the process and having released the lock. We cannot
		 * continue, since the "p" task pointer is potentially stale.
		 *
		 * Return -EAGAIN, and do_wait() will restart the loop from the
		 * beginning. Do _not_ re-acquire the lock.
		 */
		return -EAGAIN;
	}

	/* move to end of parent's list to avoid starvation */
	remove_parent(p);
1404
	add_parent(p);
L
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	write_unlock_irq(&tasklist_lock);

	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)
		retval = put_user((short)((p->ptrace & PT_PTRACED)
					  ? CLD_TRAPPED : CLD_STOPPED),
				  &infop->si_code);
	if (!retval && infop)
		retval = put_user(exit_code, &infop->si_status);
	if (!retval && infop)
		retval = put_user(p->pid, &infop->si_pid);
	if (!retval && infop)
		retval = put_user(p->uid, &infop->si_uid);
	if (!retval)
		retval = p->pid;
	put_task_struct(p);

	BUG_ON(!retval);
	return retval;
}

/*
 * Handle do_wait work for one task in a live, non-stopped state.
 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
 * the lock and this task is uninteresting.  If we return nonzero, we have
 * released the lock and the system call should return.
 */
1439
static int wait_task_continued(struct task_struct *p, int noreap,
L
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1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504
			       struct siginfo __user *infop,
			       int __user *stat_addr, struct rusage __user *ru)
{
	int retval;
	pid_t pid;
	uid_t uid;

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

	spin_lock_irq(&p->sighand->siglock);
	/* Re-check with the lock held.  */
	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
		spin_unlock_irq(&p->sighand->siglock);
		return 0;
	}
	if (!noreap)
		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
	spin_unlock_irq(&p->sighand->siglock);

	pid = p->pid;
	uid = p->uid;
	get_task_struct(p);
	read_unlock(&tasklist_lock);

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

	return retval;
}


static inline int my_ptrace_child(struct task_struct *p)
{
	if (!(p->ptrace & PT_PTRACED))
		return 0;
	if (!(p->ptrace & PT_ATTACHED))
		return 1;
	/*
	 * This child was PTRACE_ATTACH'd.  We should be seeing it only if
	 * we are the attacher.  If we are the real parent, this is a race
	 * inside ptrace_attach.  It is waiting for the tasklist_lock,
	 * which we have to switch the parent links, but has already set
	 * the flags in p->ptrace.
	 */
	return (p->parent != p->real_parent);
}

static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
		    int __user *stat_addr, struct rusage __user *ru)
{
	DECLARE_WAITQUEUE(wait, current);
	struct task_struct *tsk;
	int flag, retval;
1505
	int allowed, denied;
L
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	add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
	/*
	 * We will set this flag if we see any child that might later
	 * match our criteria, even if we are not able to reap it yet.
	 */
	flag = 0;
1514
	allowed = denied = 0;
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	current->state = TASK_INTERRUPTIBLE;
	read_lock(&tasklist_lock);
	tsk = current;
	do {
		struct task_struct *p;
		struct list_head *_p;
		int ret;

		list_for_each(_p,&tsk->children) {
1524
			p = list_entry(_p, struct task_struct, sibling);
L
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			ret = eligible_child(pid, options, p);
			if (!ret)
				continue;

1530 1531 1532 1533 1534 1535
			if (unlikely(ret < 0)) {
				denied = ret;
				continue;
			}
			allowed = 1;

L
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			switch (p->state) {
			case TASK_TRACED:
1538 1539 1540 1541 1542 1543 1544 1545 1546
				/*
				 * When we hit the race with PTRACE_ATTACH,
				 * we will not report this child.  But the
				 * race means it has not yet been moved to
				 * our ptrace_children list, so we need to
				 * set the flag here to avoid a spurious ECHILD
				 * when the race happens with the only child.
				 */
				flag = 1;
L
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1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618
				if (!my_ptrace_child(p))
					continue;
				/*FALLTHROUGH*/
			case TASK_STOPPED:
				/*
				 * It's stopped now, so it might later
				 * continue, exit, or stop again.
				 */
				flag = 1;
				if (!(options & WUNTRACED) &&
				    !my_ptrace_child(p))
					continue;
				retval = wait_task_stopped(p, ret == 2,
							   (options & WNOWAIT),
							   infop,
							   stat_addr, ru);
				if (retval == -EAGAIN)
					goto repeat;
				if (retval != 0) /* He released the lock.  */
					goto end;
				break;
			default:
			// case EXIT_DEAD:
				if (p->exit_state == EXIT_DEAD)
					continue;
			// case EXIT_ZOMBIE:
				if (p->exit_state == EXIT_ZOMBIE) {
					/*
					 * Eligible but we cannot release
					 * it yet:
					 */
					if (ret == 2)
						goto check_continued;
					if (!likely(options & WEXITED))
						continue;
					retval = wait_task_zombie(
						p, (options & WNOWAIT),
						infop, stat_addr, ru);
					/* He released the lock.  */
					if (retval != 0)
						goto end;
					break;
				}
check_continued:
				/*
				 * It's running now, so it might later
				 * exit, stop, or stop and then continue.
				 */
				flag = 1;
				if (!unlikely(options & WCONTINUED))
					continue;
				retval = wait_task_continued(
					p, (options & WNOWAIT),
					infop, stat_addr, ru);
				if (retval != 0) /* He released the lock.  */
					goto end;
				break;
			}
		}
		if (!flag) {
			list_for_each(_p, &tsk->ptrace_children) {
				p = list_entry(_p, struct task_struct,
						ptrace_list);
				if (!eligible_child(pid, options, p))
					continue;
				flag = 1;
				break;
			}
		}
		if (options & __WNOTHREAD)
			break;
		tsk = next_thread(tsk);
E
Eric Sesterhenn 已提交
1619
		BUG_ON(tsk->signal != current->signal);
L
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1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633
	} while (tsk != current);

	read_unlock(&tasklist_lock);
	if (flag) {
		retval = 0;
		if (options & WNOHANG)
			goto end;
		retval = -ERESTARTSYS;
		if (signal_pending(current))
			goto end;
		schedule();
		goto repeat;
	}
	retval = -ECHILD;
1634 1635
	if (unlikely(denied) && !allowed)
		retval = denied;
L
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1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726
end:
	current->state = TASK_RUNNING;
	remove_wait_queue(&current->signal->wait_chldexit,&wait);
	if (infop) {
		if (retval > 0)
		retval = 0;
		else {
			/*
			 * For a WNOHANG return, clear out all the fields
			 * we would set so the user can easily tell the
			 * difference.
			 */
			if (!retval)
				retval = put_user(0, &infop->si_signo);
			if (!retval)
				retval = put_user(0, &infop->si_errno);
			if (!retval)
				retval = put_user(0, &infop->si_code);
			if (!retval)
				retval = put_user(0, &infop->si_pid);
			if (!retval)
				retval = put_user(0, &infop->si_uid);
			if (!retval)
				retval = put_user(0, &infop->si_status);
		}
	}
	return retval;
}

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

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

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

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

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

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

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

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

#ifdef __ARCH_WANT_SYS_WAITPID

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

#endif