[deliverable/linux.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;
	cleanup_sighand(tsk);
	spin_unlock(&sighand->siglock);
	rcu_read_unlock();

	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 ON	116	tsk->signal = NULL;
	117	cleanup_sighand(tsk);
	118	spin_unlock(&sighand->siglock);
	119	rcu_read_unlock();
	120
	121	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
	122	flush_sigqueue(&tsk->pending);
	123	if (sig) {
	124	flush_sigqueue(&sig->shared_pending);
	125	__cleanup_signal(sig);
	126	}
	127	}
	128
1da177e4 LT	129	void release_task(struct task_struct * p)
	130	{
	131	int zap_leader;
	132	task_t *leader;
	133	struct dentry *proc_dentry;
	134
1f09f974	135	repeat:
1da177e4 LT	136	atomic_dec(&p->user->processes);
	137	spin_lock(&p->proc_lock);
	138	proc_dentry = proc_pid_unhash(p);
	139	write_lock_irq(&tasklist_lock);
1f09f974	140	ptrace_unlink(p);
1da177e4 LT	141	BUG_ON(!list_empty(&p->ptrace_list) \|\| !list_empty(&p->ptrace_children));
1da177e4 LT	142	__exit_signal(p);
35f5cad8	143
1da177e4 LT	144	/*
	145	* If we are the last non-leader member of the thread
	146	* group, and the leader is zombie, then notify the
	147	* group leader's parent process. (if it wants notification.)
	148	*/
	149	zap_leader = 0;
	150	leader = p->group_leader;
	151	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
	152	BUG_ON(leader->exit_signal == -1);
	153	do_notify_parent(leader, leader->exit_signal);
	154	/*
	155	* If we were the last child thread and the leader has
	156	* exited already, and the leader's parent ignores SIGCHLD,
	157	* then we are the one who should release the leader.
	158	*
	159	* do_notify_parent() will have marked it self-reaping in
	160	* that case.
	161	*/
	162	zap_leader = (leader->exit_signal == -1);
	163	}
	164
	165	sched_exit(p);
	166	write_unlock_irq(&tasklist_lock);
	167	spin_unlock(&p->proc_lock);
	168	proc_pid_flush(proc_dentry);
	169	release_thread(p);
	170	put_task_struct(p);
	171
	172	p = leader;
	173	if (unlikely(zap_leader))
	174	goto repeat;
	175	}
	176
1da177e4 LT	177	/*
	178	* This checks not only the pgrp, but falls back on the pid if no
	179	* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
	180	* without this...
	181	*/
	182	int session_of_pgrp(int pgrp)
	183	{
	184	struct task_struct *p;
	185	int sid = -1;
	186
	187	read_lock(&tasklist_lock);
	188	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	189	if (p->signal->session > 0) {
	190	sid = p->signal->session;
	191	goto out;
	192	}
	193	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	194	p = find_task_by_pid(pgrp);
	195	if (p)
	196	sid = p->signal->session;
	197	out:
	198	read_unlock(&tasklist_lock);
	199
	200	return sid;
	201	}
	202
	203	/*
	204	* Determine if a process group is "orphaned", according to the POSIX
	205	* definition in 2.2.2.52. Orphaned process groups are not to be affected
	206	* by terminal-generated stop signals. Newly orphaned process groups are
	207	* to receive a SIGHUP and a SIGCONT.
	208	*
	209	* "I ask you, have you ever known what it is to be an orphan?"
	210	*/
	211	static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
	212	{
	213	struct task_struct *p;
	214	int ret = 1;
	215
	216	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	217	if (p == ignored_task
	218	\|\| p->exit_state
	219	\|\| p->real_parent->pid == 1)
	220	continue;
	221	if (process_group(p->real_parent) != pgrp
	222	&& p->real_parent->signal->session == p->signal->session) {
	223	ret = 0;
	224	break;
	225	}
	226	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	227	return ret; /* (sighing) "Often!" */
	228	}
	229
	230	int is_orphaned_pgrp(int pgrp)
	231	{
	232	int retval;
	233
	234	read_lock(&tasklist_lock);
	235	retval = will_become_orphaned_pgrp(pgrp, NULL);
	236	read_unlock(&tasklist_lock);
	237
	238	return retval;
	239	}
	240
858119e1	241	static int has_stopped_jobs(int pgrp)
1da177e4 LT	242	{
	243	int retval = 0;
	244	struct task_struct *p;
	245
	246	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	247	if (p->state != TASK_STOPPED)
	248	continue;
	249
	250	/* If p is stopped by a debugger on a signal that won't
	251	stop it, then don't count p as stopped. This isn't
	252	perfect but it's a good approximation. */
	253	if (unlikely (p->ptrace)
	254	&& p->exit_code != SIGSTOP
	255	&& p->exit_code != SIGTSTP
	256	&& p->exit_code != SIGTTOU
	257	&& p->exit_code != SIGTTIN)
	258	continue;
	259
	260	retval = 1;
	261	break;
	262	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	263	return retval;
	264	}
	265
	266	/**
4dc3b16b	267	* reparent_to_init - Reparent the calling kernel thread to the init task.
1da177e4 LT	268	*
	269	* If a kernel thread is launched as a result of a system call, or if
	270	* it ever exits, it should generally reparent itself to init so that
	271	* it is correctly cleaned up on exit.
	272	*
	273	* The various task state such as scheduling policy and priority may have
	274	* been inherited from a user process, so we reset them to sane values here.
	275	*
	276	* NOTE that reparent_to_init() gives the caller full capabilities.
	277	*/
858119e1	278	static void reparent_to_init(void)
1da177e4 LT	279	{
	280	write_lock_irq(&tasklist_lock);
	281
	282	ptrace_unlink(current);
	283	/* Reparent to init */
9b678ece	284	remove_parent(current);
1da177e4 LT	285	current->parent = child_reaper;
1da177e4 LT	286	current->real_parent = child_reaper;
9b678ece	287	add_parent(current);
1da177e4 LT	288
	289	/* Set the exit signal to SIGCHLD so we signal init on exit */
	290	current->exit_signal = SIGCHLD;
	291
b0a9499c IM	292	if ((current->policy == SCHED_NORMAL \|\|
	293	current->policy == SCHED_BATCH)
	294	&& (task_nice(current) < 0))
1da177e4 LT	295	set_user_nice(current, 0);
	296	/* cpus_allowed? */
	297	/* rt_priority? */
	298	/* signals? */
	299	security_task_reparent_to_init(current);
	300	memcpy(current->signal->rlim, init_task.signal->rlim,
	301	sizeof(current->signal->rlim));
	302	atomic_inc(&(INIT_USER->__count));
	303	write_unlock_irq(&tasklist_lock);
	304	switch_uid(INIT_USER);
	305	}
	306
	307	void __set_special_pids(pid_t session, pid_t pgrp)
	308	{
e19f247a	309	struct task_struct *curr = current->group_leader;
1da177e4 LT	310
	311	if (curr->signal->session != session) {
	312	detach_pid(curr, PIDTYPE_SID);
	313	curr->signal->session = session;
	314	attach_pid(curr, PIDTYPE_SID, session);
	315	}
	316	if (process_group(curr) != pgrp) {
	317	detach_pid(curr, PIDTYPE_PGID);
	318	curr->signal->pgrp = pgrp;
	319	attach_pid(curr, PIDTYPE_PGID, pgrp);
	320	}
	321	}
	322
	323	void set_special_pids(pid_t session, pid_t pgrp)
	324	{
	325	write_lock_irq(&tasklist_lock);
	326	__set_special_pids(session, pgrp);
	327	write_unlock_irq(&tasklist_lock);
	328	}
	329
	330	/*
	331	* Let kernel threads use this to say that they
	332	* allow a certain signal (since daemonize() will
	333	* have disabled all of them by default).
	334	*/
	335	int allow_signal(int sig)
	336	{
7ed20e1a	337	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	338	return -EINVAL;
	339
	340	spin_lock_irq(&current->sighand->siglock);
	341	sigdelset(&current->blocked, sig);
	342	if (!current->mm) {
	343	/* Kernel threads handle their own signals.
	344	Let the signal code know it'll be handled, so
	345	that they don't get converted to SIGKILL or
	346	just silently dropped */
	347	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
	348	}
	349	recalc_sigpending();
	350	spin_unlock_irq(&current->sighand->siglock);
	351	return 0;
	352	}
	353
	354	EXPORT_SYMBOL(allow_signal);
	355
	356	int disallow_signal(int sig)
	357	{
7ed20e1a	358	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	359	return -EINVAL;
	360
	361	spin_lock_irq(&current->sighand->siglock);
	362	sigaddset(&current->blocked, sig);
	363	recalc_sigpending();
	364	spin_unlock_irq(&current->sighand->siglock);
	365	return 0;
	366	}
	367
	368	EXPORT_SYMBOL(disallow_signal);
	369
	370	/*
	371	* Put all the gunge required to become a kernel thread without
	372	* attached user resources in one place where it belongs.
	373	*/
	374
	375	void daemonize(const char *name, ...)
	376	{
	377	va_list args;
	378	struct fs_struct *fs;
	379	sigset_t blocked;
	380
	381	va_start(args, name);
	382	vsnprintf(current->comm, sizeof(current->comm), name, args);
	383	va_end(args);
	384
	385	/*
	386	* If we were started as result of loading a module, close all of the
	387	* user space pages. We don't need them, and if we didn't close them
	388	* they would be locked into memory.
	389	*/
	390	exit_mm(current);
	391
	392	set_special_pids(1, 1);
70522e12	393	mutex_lock(&tty_mutex);
1da177e4	394	current->signal->tty = NULL;
70522e12	395	mutex_unlock(&tty_mutex);
1da177e4 LT	396
	397	/* Block and flush all signals */
	398	sigfillset(&blocked);
	399	sigprocmask(SIG_BLOCK, &blocked, NULL);
	400	flush_signals(current);
	401
	402	/* Become as one with the init task */
	403
	404	exit_fs(current); /* current->fs->count--; */
	405	fs = init_task.fs;
	406	current->fs = fs;
	407	atomic_inc(&fs->count);