exit.c 41.7 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/smp_lock.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>
#include <linux/namespace.h>
#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
#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/cpuset.h>
#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 <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

extern void sem_exit (void);
extern struct task_struct *child_reaper;

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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:
		 */
		if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
			wake_up_process(sig->group_exit_task);
			sig->group_exit_task = NULL;
		}
		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);
		sig->min_flt += tsk->min_flt;
		sig->maj_flt += tsk->maj_flt;
		sig->nvcsw += tsk->nvcsw;
		sig->nivcsw += tsk->nivcsw;
		sig->sched_time += tsk->sched_time;
		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);
		__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);
	}

	sched_exit(p);
	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...
 */
int session_of_pgrp(int pgrp)
{
	struct task_struct *p;
	int sid = -1;

	read_lock(&tasklist_lock);
	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
		if (p->signal->session > 0) {
			sid = p->signal->session;
			goto out;
		}
	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	p = find_task_by_pid(pgrp);
	if (p)
		sid = p->signal->session;
out:
	read_unlock(&tasklist_lock);
	
	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(int pgrp, struct task_struct *ignored_task)
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{
	struct task_struct *p;
	int ret = 1;

	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
		if (p == ignored_task
				|| p->exit_state
				|| p->real_parent->pid == 1)
			continue;
		if (process_group(p->real_parent) != pgrp
			    && p->real_parent->signal->session == p->signal->session) {
			ret = 0;
			break;
		}
	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	return ret;	/* (sighing) "Often!" */
}

int is_orphaned_pgrp(int pgrp)
{
	int retval;

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

	return retval;
}

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

	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
		if (p->state != TASK_STOPPED)
			continue;

		/* If p is stopped by a debugger on a signal that won't
		   stop it, then don't count p as stopped.  This isn't
		   perfect but it's a good approximation.  */
		if (unlikely (p->ptrace)
		    && p->exit_code != SIGSTOP
		    && p->exit_code != SIGTSTP
		    && p->exit_code != SIGTTOU
		    && p->exit_code != SIGTTIN)
			continue;

		retval = 1;
		break;
	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	return retval;
}

/**
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 * reparent_to_init - Reparent the calling kernel thread to the init task.
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 *
 * If a kernel thread is launched as a result of a system call, or if
 * it ever exits, it should generally reparent itself to init so that
 * it is correctly cleaned up on exit.
 *
 * 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.
 *
 * NOTE that reparent_to_init() gives the caller full capabilities.
 */
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static void reparent_to_init(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->parent = child_reaper;
	current->real_parent = child_reaper;
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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 ((current->policy == SCHED_NORMAL ||
			current->policy == SCHED_BATCH)
				&& (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 (curr->signal->session != session) {
		detach_pid(curr, PIDTYPE_SID);
		curr->signal->session = session;
		attach_pid(curr, PIDTYPE_SID, session);
	}
	if (process_group(curr) != pgrp) {
		detach_pid(curr, PIDTYPE_PGID);
		curr->signal->pgrp = pgrp;
		attach_pid(curr, PIDTYPE_PGID, pgrp);
	}
}

void set_special_pids(pid_t session, pid_t pgrp)
{
	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);
	sigaddset(&current->blocked, sig);
	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);

	set_special_pids(1, 1);
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	mutex_lock(&tty_mutex);
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	current->signal->tty = NULL;
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	mutex_unlock(&tty_mutex);
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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_namespace(current);
	current->namespace = init_task.namespace;
	get_namespace(current->namespace);
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 	exit_files(current);
	current->files = init_task.files;
	atomic_inc(&current->files->count);

	reparent_to_init();
}

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_fdset || 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)
					filp_close(file, files);
			}
			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)
			fdt->free_files = files;
		else
			kmem_cache_free(files_cachep, files);
		free_fdtable(fdt);
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	}
}

EXPORT_SYMBOL(put_files_struct);

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);
	task_unlock(tsk);
	mmput(mm);
}

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static inline void
choose_new_parent(struct task_struct *p, struct task_struct *reaper)
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{
	/*
	 * Make sure we're not reparenting to ourselves and that
	 * the parent is not a zombie.
	 */
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	BUG_ON(p == reaper || reaper->exit_state);
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	p->real_parent = reaper;
}

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static void
reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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{
	/* We don't want people slaying init.  */
	if (p->exit_signal != -1)
		p->exit_signal = SIGCHLD;

	if (p->pdeath_signal)
		/* We already hold the tasklist_lock here.  */
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		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;
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		remove_parent(p);
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		p->parent = p->real_parent;
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		add_parent(p);
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		/* If we'd notified the old parent about this child's death,
		 * also notify the new parent.
		 */
		if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
		    thread_group_empty(p))
			do_notify_parent(p, p->exit_signal);
		else if (p->state == TASK_TRACED) {
			/*
			 * If it was at a trace stop, turn it into
			 * a normal stop since it's no longer being
			 * traced.
			 */
			ptrace_untrace(p);
		}
	}

	/*
	 * 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.
	 */
	if ((process_group(p) != process_group(father)) &&
	    (p->signal->session == father->signal->session)) {
		int pgrp = process_group(p);

		if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
651 652
			__kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp);
			__kill_pg_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
 * the global child reaper process (ie "init")
 */
663 664
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) {
			reaper = child_reaper;
			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;
687
		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 */
696
			choose_new_parent(p, 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) {
716
		p = list_entry(_p, struct task_struct, ptrace_list);
717
		choose_new_parent(p, 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;

	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.
		 */
		read_lock(&tasklist_lock);
		spin_lock_irq(&tsk->sighand->siglock);
		for (t = next_thread(tsk); t != tsk; t = next_thread(t))
			if (!signal_pending(t) && !(t->flags & PF_EXITING)) {
				recalc_sigpending_tsk(t);
				if (signal_pending(t))
					signal_wake_up(t, 0);
			}
		spin_unlock_irq(&tsk->sighand->siglock);
		read_unlock(&tasklist_lock);
	}

	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;
	
	if ((process_group(t) != process_group(tsk)) &&
	    (t->signal->session == tsk->signal->session) &&
	    will_become_orphaned_pgrp(process_group(tsk), tsk) &&
	    has_stopped_jobs(process_group(tsk))) {
787 788
		__kill_pg_info(SIGHUP, SEND_SIG_PRIV, process_group(tsk));
		__kill_pg_info(SIGCONT, SEND_SIG_PRIV, process_group(tsk));
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	}

	/* Let father know we died 
	 *
	 * 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;
	if (tsk->exit_signal == -1 &&
	    (likely(tsk->ptrace == 0) ||
	     unlikely(tsk->parent->signal->flags & SIGNAL_GROUP_EXIT)))
		state = EXIT_DEAD;
	tsk->exit_state = state;

	write_unlock_irq(&tasklist_lock);

	list_for_each_safe(_p, _n, &ptrace_dead) {
		list_del_init(_p);
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		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);
}

fastcall NORET_TYPE void do_exit(long code)
{
	struct task_struct *tsk = current;
848
	struct taskstats *tidstats;
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	int group_dead;
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	unsigned int mycpu;
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	profile_task_exit(tsk);

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	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!");
860
	if (unlikely(tsk == child_reaper))
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		panic("Attempted to kill init!");

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

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	/*
	 * 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");
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		if (tsk->io_context)
			exit_io_context();
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		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule();
	}

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	tsk->flags |= PF_EXITING;

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

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	taskstats_exit_alloc(&tidstats, &mycpu);
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	acct_update_integrals(tsk);
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	if (tsk->mm) {
		update_hiwater_rss(tsk->mm);
		update_hiwater_vm(tsk->mm);
	}
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	group_dead = atomic_dec_and_test(&tsk->signal->live);
896
	if (group_dead) {
897
 		hrtimer_cancel(&tsk->signal->real_timer);
898
		exit_itimers(tsk->signal);
899
	}
900
	acct_collect(code, group_dead);
901 902
	if (unlikely(tsk->robust_list))
		exit_robust_list(tsk);
903
#if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
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	if (unlikely(tsk->compat_robust_list))
		compat_exit_robust_list(tsk);
#endif
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	if (unlikely(tsk->audit_context))
		audit_free(tsk);
909
	taskstats_exit_send(tsk, tidstats, group_dead, mycpu);
910
	taskstats_exit_free(tidstats);
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	exit_mm(tsk);

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	if (group_dead)
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		acct_process();
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	exit_sem(tsk);
	__exit_files(tsk);
	__exit_fs(tsk);
	exit_namespace(tsk);
	exit_thread();
	cpuset_exit(tsk);
	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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	if (tsk->binfmt)
		module_put(tsk->binfmt->module);

	tsk->exit_code = code;
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	proc_exit_connector(tsk);
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	exit_notify(tsk);
#ifdef CONFIG_NUMA
	mpol_free(tsk->mempolicy);
	tsk->mempolicy = NULL;
#endif
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	/*
	 * 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);
946
	/*
947
	 * Make sure we are holding no locks:
948
	 */
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	debug_check_no_locks_held(tsk);
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	if (tsk->io_context)
		exit_io_context();

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

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	/* PF_DEAD causes final put_task_struct after we schedule. */
	preempt_disable();
	BUG_ON(tsk->flags & PF_DEAD);
	tsk->flags |= PF_DEAD;

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	schedule();
	BUG();
	/* Avoid "noreturn function does return".  */
	for (;;) ;
}

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EXPORT_SYMBOL_GPL(do_exit);

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

1024
static int eligible_child(pid_t pid, int options, struct task_struct *p)
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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:
	 */
1056
	if (delay_group_leader(p))
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		return 2;

	if (security_task_wait(p))
		return 0;

	return 1;
}

1065
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;
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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.
 */
1096
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;
	int retval;
	int status;

	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;
	}
	if (unlikely(p->exit_signal == -1 && p->ptrace == 0)) {
		/*
		 * This can only happen in a race with a ptraced thread
		 * dying on another processor.
		 */
		return 0;
	}

	if (likely(p->real_parent == p->parent) && likely(p->signal)) {
1145 1146 1147
		struct signal_struct *psig;
		struct signal_struct *sig;

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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);
1164 1165 1166 1167
		psig = p->parent->signal;
		sig = p->signal;
		psig->cutime =
			cputime_add(psig->cutime,
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			cputime_add(p->utime,
1169 1170 1171 1172
			cputime_add(sig->utime,
				    sig->cutime)));
		psig->cstime =
			cputime_add(psig->cstime,
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			cputime_add(p->stime,
1174 1175 1176 1177 1178 1179 1180 1181 1182 1183
			cputime_add(sig->stime,
				    sig->cstime)));
		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;
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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);
	if (retval) {
		// TODO: is this safe?
		p->exit_state = EXIT_ZOMBIE;
		return retval;
	}
	retval = p->pid;
	if (p->real_parent != p->parent) {
		write_lock_irq(&tasklist_lock);
		/* Double-check with lock held.  */
		if (p->real_parent != p->parent) {
			__ptrace_unlink(p);
			// TODO: is this safe?
			p->exit_state = EXIT_ZOMBIE;
			/*
			 * 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);
				if (p->exit_signal != -1)
					p = NULL;
			}
		}
		write_unlock_irq(&tasklist_lock);
	}
	if (p != NULL)
		release_task(p);
	BUG_ON(!retval);
	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.
 */
1258 1259
static int wait_task_stopped(struct task_struct *p, int delayed_group_leader,
			     int noreap, struct siginfo __user *infop,
L
Linus Torvalds 已提交
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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) &&
	    p->signal && p->signal->group_stop_count > 0)
		/*
		 * 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) ||
1291
		    unlikely(p->state & TASK_TRACED))
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Linus Torvalds 已提交
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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);
1338
	add_parent(p);
L
Linus Torvalds 已提交
1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372

	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.
 */
1373
static int wait_task_continued(struct task_struct *p, int noreap,
L
Linus Torvalds 已提交
1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458
			       struct siginfo __user *infop,
			       int __user *stat_addr, struct rusage __user *ru)
{
	int retval;
	pid_t pid;
	uid_t uid;

	if (unlikely(!p->signal))
		return 0;

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

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

	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;
	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) {
1459
			p = list_entry(_p, struct task_struct, sibling);
L
Linus Torvalds 已提交
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			ret = eligible_child(pid, options, p);
			if (!ret)
				continue;

			switch (p->state) {
			case TASK_TRACED:
1467 1468 1469 1470 1471 1472 1473 1474 1475
				/*
				 * 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
Linus Torvalds 已提交
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 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547
				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
1548
		BUG_ON(tsk->signal != current->signal);
L
Linus Torvalds 已提交
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 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653
	} 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;
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