[linux-2.6-block.git] / kernel / exit.c

/*
 *  linux/kernel/exit.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/config.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/capability.h>
#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>
#include <linux/cpuset.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/posix-timers.h>
#include <linux/cn_proc.h>
#include <linux/mutex.h>
#include <linux/futex.h>
#include <linux/compat.h>

#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;

int getrusage(struct task_struct *, int, struct rusage __user *);

static void exit_mm(struct task_struct * tsk);

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);

		list_del_init(&p->tasks);
		__get_cpu_var(process_counts)--;
	}
	list_del_rcu(&p->thread_group);
	remove_parent(p);
}

/*
 * 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. */
	}

	__unhash_process(tsk);

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

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

void release_task(struct task_struct * p)
{
	int zap_leader;
	task_t *leader;
	struct dentry *proc_dentry;

repeat:
	atomic_dec(&p->user->processes);
	spin_lock(&p->proc_lock);
	proc_dentry = proc_pid_unhash(p);
	write_lock_irq(&tasklist_lock);
	ptrace_unlink(p);
	BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
	__exit_signal(p);

	/*
	 * 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);
	spin_unlock(&p->proc_lock);
	proc_pid_flush(proc_dentry);
	release_thread(p);
	put_task_struct(p);

	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?"
 */
static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
{
	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;
}

static int has_stopped_jobs(int pgrp)
{
	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;
}

/**
 * reparent_to_init - Reparent the calling kernel thread to the init task.
 *
 * 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.
 */
static void reparent_to_init(void)
{
	write_lock_irq(&tasklist_lock);

	ptrace_unlink(current);
	/* Reparent to init */
	remove_parent(current);
	current->parent = child_reaper;
	current->real_parent = child_reaper;
	add_parent(current);

	/* Set the exit signal to SIGCHLD so we signal init on exit */
	current->exit_signal = SIGCHLD;

	if ((current->policy == SCHED_NORMAL ||
			current->policy == SCHED_BATCH)
				&& (task_nice(current) < 0))
		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)
{
	struct task_struct *curr = current->group_leader;

	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)
{
	if (!valid_signal(sig) || sig < 1)
		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)
{
	if (!valid_signal(sig) || sig < 1)
		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);
	mutex_lock(&tty_mutex);
	current->signal->tty = NULL;
	mutex_unlock(&tty_mutex);

	/* 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);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/kernel/exit.c
	3	*
	4	* Copyright (C) 1991, 1992 Linus Torvalds
	5	*/
	6
	7	#include <linux/config.h>
	8	#include <linux/mm.h>
	9	#include <linux/slab.h>
	10	#include <linux/interrupt.h>
	11	#include <linux/smp_lock.h>
	12	#include <linux/module.h>
c59ede7b	13	#include <linux/capability.h>
1da177e4 LT	14	#include <linux/completion.h>
	15	#include <linux/personality.h>
	16	#include <linux/tty.h>
	17	#include <linux/namespace.h>
	18	#include <linux/key.h>
	19	#include <linux/security.h>
	20	#include <linux/cpu.h>
	21	#include <linux/acct.h>
	22	#include <linux/file.h>
	23	#include <linux/binfmts.h>
	24	#include <linux/ptrace.h>
	25	#include <linux/profile.h>
	26	#include <linux/mount.h>
	27	#include <linux/proc_fs.h>
	28	#include <linux/mempolicy.h>
	29	#include <linux/cpuset.h>
	30	#include <linux/syscalls.h>
7ed20e1a	31	#include <linux/signal.h>
6a14c5c9	32	#include <linux/posix-timers.h>
9f46080c	33	#include <linux/cn_proc.h>
de5097c2	34	#include <linux/mutex.h>
0771dfef	35	#include <linux/futex.h>
34f192c6	36	#include <linux/compat.h>
1da177e4 LT	37
	38	#include <asm/uaccess.h>
	39	#include <asm/unistd.h>
	40	#include <asm/pgtable.h>
	41	#include <asm/mmu_context.h>
	42
	43	extern void sem_exit (void);
	44	extern struct task_struct *child_reaper;
	45
	46	int getrusage(struct task_struct , int, struct rusage __user );
	47
408b664a AB	48	static void exit_mm(struct task_struct * tsk);
408b664a AB	49
1da177e4 LT	50	static void __unhash_process(struct task_struct *p)
	51	{
	52	nr_threads--;
	53	detach_pid(p, PIDTYPE_PID);
1da177e4 LT	54	if (thread_group_leader(p)) {
	55	detach_pid(p, PIDTYPE_PGID);
	56	detach_pid(p, PIDTYPE_SID);
c97d9893 ON	57
c97d9893 ON	58	list_del_init(&p->tasks);
73b9ebfe	59	__get_cpu_var(process_counts)--;
1da177e4	60	}
47e65328	61	list_del_rcu(&p->thread_group);
c97d9893	62	remove_parent(p);
1da177e4 LT	63	}
1da177e4 LT	64
6a14c5c9 ON	65	/*
	66	* This function expects the tasklist_lock write-locked.
	67	*/
	68	static void __exit_signal(struct task_struct *tsk)
	69	{
	70	struct signal_struct *sig = tsk->signal;
	71	struct sighand_struct *sighand;
	72
	73	BUG_ON(!sig);
	74	BUG_ON(!atomic_read(&sig->count));
	75
	76	rcu_read_lock();
	77	sighand = rcu_dereference(tsk->sighand);
	78	spin_lock(&sighand->siglock);
	79
	80	posix_cpu_timers_exit(tsk);
	81	if (atomic_dec_and_test(&sig->count))
	82	posix_cpu_timers_exit_group(tsk);
	83	else {
	84	/*
	85	* If there is any task waiting for the group exit
	86	* then notify it:
	87	*/
	88	if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
	89	wake_up_process(sig->group_exit_task);
	90	sig->group_exit_task = NULL;
	91	}
	92	if (tsk == sig->curr_target)
	93	sig->curr_target = next_thread(tsk);
	94	/*
	95	* Accumulate here the counters for all threads but the
	96	* group leader as they die, so they can be added into
	97	* the process-wide totals when those are taken.
	98	* The group leader stays around as a zombie as long
	99	* as there are other threads. When it gets reaped,
	100	* the exit.c code will add its counts into these totals.
	101	* We won't ever get here for the group leader, since it
	102	* will have been the last reference on the signal_struct.
	103	*/
	104	sig->utime = cputime_add(sig->utime, tsk->utime);
	105	sig->stime = cputime_add(sig->stime, tsk->stime);
	106	sig->min_flt += tsk->min_flt;
	107	sig->maj_flt += tsk->maj_flt;
	108	sig->nvcsw += tsk->nvcsw;
	109	sig->nivcsw += tsk->nivcsw;
	110	sig->sched_time += tsk->sched_time;
	111	sig = NULL; /* Marker for below. */
	112	}
	113
5876700c ON	114	__unhash_process(tsk);
5876700c ON	115
6a14c5c9	116	tsk->signal = NULL;
a7e5328a	117	tsk->sighand = NULL;
6a14c5c9 ON	118	spin_unlock(&sighand->siglock);
	119	rcu_read_unlock();
	120
a7e5328a	121	__cleanup_sighand(sighand);
6a14c5c9 ON	122	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
	123	flush_sigqueue(&tsk->pending);
	124	if (sig) {
	125	flush_sigqueue(&sig->shared_pending);
	126	__cleanup_signal(sig);
	127	}
	128	}
	129
1da177e4 LT	130	void release_task(struct task_struct * p)
	131	{
	132	int zap_leader;
	133	task_t *leader;
	134	struct dentry *proc_dentry;
	135
1f09f974	136	repeat:
1da177e4 LT	137	atomic_dec(&p->user->processes);
	138	spin_lock(&p->proc_lock);
	139	proc_dentry = proc_pid_unhash(p);
	140	write_lock_irq(&tasklist_lock);
1f09f974	141	ptrace_unlink(p);
1da177e4 LT	142	BUG_ON(!list_empty(&p->ptrace_list) \|\| !list_empty(&p->ptrace_children));
1da177e4 LT	143	__exit_signal(p);
35f5cad8	144
1da177e4 LT	145	/*
	146	* If we are the last non-leader member of the thread
	147	* group, and the leader is zombie, then notify the
	148	* group leader's parent process. (if it wants notification.)
	149	*/
	150	zap_leader = 0;
	151	leader = p->group_leader;
	152	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
	153	BUG_ON(leader->exit_signal == -1);
	154	do_notify_parent(leader, leader->exit_signal);
	155	/*
	156	* If we were the last child thread and the leader has
	157	* exited already, and the leader's parent ignores SIGCHLD,
	158	* then we are the one who should release the leader.
	159	*
	160	* do_notify_parent() will have marked it self-reaping in
	161	* that case.
	162	*/
	163	zap_leader = (leader->exit_signal == -1);
	164	}
	165
	166	sched_exit(p);
	167	write_unlock_irq(&tasklist_lock);
	168	spin_unlock(&p->proc_lock);
	169	proc_pid_flush(proc_dentry);
	170	release_thread(p);
	171	put_task_struct(p);
	172
	173	p = leader;
	174	if (unlikely(zap_leader))
	175	goto repeat;
	176	}
	177
1da177e4 LT	178	/*
	179	* This checks not only the pgrp, but falls back on the pid if no
	180	* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
	181	* without this...
	182	*/
	183	int session_of_pgrp(int pgrp)
	184	{
	185	struct task_struct *p;
	186	int sid = -1;
	187
	188	read_lock(&tasklist_lock);
	189	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	190	if (p->signal->session > 0) {
	191	sid = p->signal->session;
	192	goto out;
	193	}
	194	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	195	p = find_task_by_pid(pgrp);
	196	if (p)
	197	sid = p->signal->session;
	198	out:
	199	read_unlock(&tasklist_lock);
	200
	201	return sid;
	202	}
	203
	204	/*
	205	* Determine if a process group is "orphaned", according to the POSIX
	206	* definition in 2.2.2.52. Orphaned process groups are not to be affected
	207	* by terminal-generated stop signals. Newly orphaned process groups are
	208	* to receive a SIGHUP and a SIGCONT.
	209	*
	210	* "I ask you, have you ever known what it is to be an orphan?"
	211	*/
	212	static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
	213	{
	214	struct task_struct *p;
	215	int ret = 1;
	216
	217	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	218	if (p == ignored_task
	219	\|\| p->exit_state
	220	\|\| p->real_parent->pid == 1)
	221	continue;
	222	if (process_group(p->real_parent) != pgrp
	223	&& p->real_parent->signal->session == p->signal->session) {
	224	ret = 0;
	225	break;
	226	}
	227	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	228	return ret; /* (sighing) "Often!" */
	229	}
	230
	231	int is_orphaned_pgrp(int pgrp)
	232	{
	233	int retval;
	234
	235	read_lock(&tasklist_lock);
	236	retval = will_become_orphaned_pgrp(pgrp, NULL);
	237	read_unlock(&tasklist_lock);
	238
	239	return retval;
	240	}
	241
858119e1	242	static int has_stopped_jobs(int pgrp)
1da177e4 LT	243	{
	244	int retval = 0;
	245	struct task_struct *p;
	246
	247	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	248	if (p->state != TASK_STOPPED)
	249	continue;
	250
	251	/* If p is stopped by a debugger on a signal that won't
	252	stop it, then don't count p as stopped. This isn't
	253	perfect but it's a good approximation. */
	254	if (unlikely (p->ptrace)
	255	&& p->exit_code != SIGSTOP
	256	&& p->exit_code != SIGTSTP
	257	&& p->exit_code != SIGTTOU
	258	&& p->exit_code != SIGTTIN)
	259	continue;
	260
	261	retval = 1;
	262	break;
	263	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	264	return retval;
	265	}
	266
	267	/**
4dc3b16b	268	* reparent_to_init - Reparent the calling kernel thread to the init task.
1da177e4 LT	269	*
	270	* If a kernel thread is launched as a result of a system call, or if
	271	* it ever exits, it should generally reparent itself to init so that
	272	* it is correctly cleaned up on exit.
	273	*
	274	* The various task state such as scheduling policy and priority may have
	275	* been inherited from a user process, so we reset them to sane values here.
	276	*
	277	* NOTE that reparent_to_init() gives the caller full capabilities.
	278	*/
858119e1	279	static void reparent_to_init(void)
1da177e4 LT	280	{
	281	write_lock_irq(&tasklist_lock);
	282
	283	ptrace_unlink(current);
	284	/* Reparent to init */
9b678ece	285	remove_parent(current);
1da177e4 LT	286	current->parent = child_reaper;
1da177e4 LT	287	current->real_parent = child_reaper;
9b678ece	288	add_parent(current);
1da177e4 LT	289
	290	/* Set the exit signal to SIGCHLD so we signal init on exit */
	291	current->exit_signal = SIGCHLD;
	292
b0a9499c IM	293	if ((current->policy == SCHED_NORMAL \|\|
	294	current->policy == SCHED_BATCH)
	295	&& (task_nice(current) < 0))
1da177e4 LT	296	set_user_nice(current, 0);
	297	/* cpus_allowed? */
	298	/* rt_priority? */
	299	/* signals? */
	300	security_task_reparent_to_init(current);
	301	memcpy(current->signal->rlim, init_task.signal->rlim,
	302	sizeof(current->signal->rlim));
	303	atomic_inc(&(INIT_USER->__count));
	304	write_unlock_irq(&tasklist_lock);
	305	switch_uid(INIT_USER);
	306	}
	307
	308	void __set_special_pids(pid_t session, pid_t pgrp)
	309	{
e19f247a	310	struct task_struct *curr = current->group_leader;
1da177e4 LT	311
	312	if (curr->signal->session != session) {
	313	detach_pid(curr, PIDTYPE_SID);
	314	curr->signal->session = session;
	315	attach_pid(curr, PIDTYPE_SID, session);
	316	}
	317	if (process_group(curr) != pgrp) {
	318	detach_pid(curr, PIDTYPE_PGID);
	319	curr->signal->pgrp = pgrp;
	320	attach_pid(curr, PIDTYPE_PGID, pgrp);
	321	}
	322	}
	323
	324	void set_special_pids(pid_t session, pid_t pgrp)
	325	{
	326	write_lock_irq(&tasklist_lock);
	327	__set_special_pids(session, pgrp);
	328	write_unlock_irq(&tasklist_lock);
	329	}
	330
	331	/*
	332	* Let kernel threads use this to say that they
	333	* allow a certain signal (since daemonize() will
	334	* have disabled all of them by default).
	335	*/
	336	int allow_signal(int sig)
	337	{
7ed20e1a	338	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	339	return -EINVAL;
	340
	341	spin_lock_irq(&current->sighand->siglock);
	342	sigdelset(&current->blocked, sig);
	343	if (!current->mm) {
	344	/* Kernel threads handle their own signals.
	345	Let the signal code know it'll be handled, so
	346	that they don't get converted to SIGKILL or
	347	just silently dropped */
	348	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
	349	}
	350	recalc_sigpending();
	351	spin_unlock_irq(&current->sighand->siglock);
	352	return 0;
	353	}
	354
	355	EXPORT_SYMBOL(allow_signal);
	356
	357	int disallow_signal(int sig)
	358	{
7ed20e1a	359	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	360	return -EINVAL;
	361
	362	spin_lock_irq(&current->sighand->siglock);
	363	sigaddset(&current->blocked, sig);
	364	recalc_sigpending();
	365	spin_unlock_irq(&current->sighand->siglock);
	366	return 0;
	367	}
	368
	369	EXPORT_SYMBOL(disallow_signal);
	370
	371	/*
	372	* Put all the gunge required to become a kernel thread without
	373	* attached user resources in one place where it belongs.
	374	*/
	375
	376	void daemonize(const char *name, ...)
	377	{
	378	va_list args;
	379	struct fs_struct *fs;
	380	sigset_t blocked;
	381
	382	va_start(args, name);
	383	vsnprintf(current->comm, sizeof(current->comm), name, args);
	384	va_end(args);
	385
	386	/*
	387	* If we were started as result of loading a module, close all of the
	388	* user space pages. We don't need them, and if we didn't close them
	389	* they would be locked into memory.
	390	*/
	391	exit_mm(current);
	392
	393	set_special_pids(1, 1);
70522e12	394	mutex_lock(&tty_mutex);
1da177e4	395	current->signal->tty = NULL;
70522e12	396	mutex_unlock(&tty_mutex);
1da177e4 LT	397
	398	/* Block and flush all signals */
	399	sigfillset(&blocked);
	400	sigprocmask(SIG_BLOCK, &blocked, NULL);
	401	flush_signals(current);
	402
	403	/* Become as one with the init task */
	404
	405	exit_fs(current); /* current->fs->count--; */
	406	fs = init_task.fs;
	407	current->fs = fs;
	408	atomic_inc(&fs->count);