[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 <linux/pipe_fs_i.h>
#include <linux/audit.h> /* for audit_free() */

#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_rcu(&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);
	}
}

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

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);
	call_rcu(&p->rcu, delayed_put_task_struct);

	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>
b92ce558	37	#include <linux/pipe_fs_i.h>
fa84cb93	38	#include <linux/audit.h> /* for audit_free() */
1da177e4 LT	39
	40	#include <asm/uaccess.h>
	41	#include <asm/unistd.h>
	42	#include <asm/pgtable.h>
	43	#include <asm/mmu_context.h>
	44
	45	extern void sem_exit (void);
	46	extern struct task_struct *child_reaper;
	47
	48	int getrusage(struct task_struct , int, struct rusage __user );
	49
408b664a AB	50	static void exit_mm(struct task_struct * tsk);
408b664a AB	51
1da177e4 LT	52	static void __unhash_process(struct task_struct *p)
	53	{
	54	nr_threads--;
	55	detach_pid(p, PIDTYPE_PID);
1da177e4 LT	56	if (thread_group_leader(p)) {
	57	detach_pid(p, PIDTYPE_PGID);
	58	detach_pid(p, PIDTYPE_SID);
c97d9893	59
5e85d4ab	60	list_del_rcu(&p->tasks);
73b9ebfe	61	__get_cpu_var(process_counts)--;
1da177e4	62	}
47e65328	63	list_del_rcu(&p->thread_group);
c97d9893	64	remove_parent(p);
1da177e4 LT	65	}
1da177e4 LT	66
6a14c5c9 ON	67	/*
	68	* This function expects the tasklist_lock write-locked.
	69	*/
	70	static void __exit_signal(struct task_struct *tsk)
	71	{
	72	struct signal_struct *sig = tsk->signal;
	73	struct sighand_struct *sighand;
	74
	75	BUG_ON(!sig);
	76	BUG_ON(!atomic_read(&sig->count));
	77
	78	rcu_read_lock();
	79	sighand = rcu_dereference(tsk->sighand);
	80	spin_lock(&sighand->siglock);
	81
	82	posix_cpu_timers_exit(tsk);
	83	if (atomic_dec_and_test(&sig->count))
	84	posix_cpu_timers_exit_group(tsk);
	85	else {
	86	/*
	87	* If there is any task waiting for the group exit
	88	* then notify it:
	89	*/
	90	if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) {
	91	wake_up_process(sig->group_exit_task);
	92	sig->group_exit_task = NULL;
	93	}
	94	if (tsk == sig->curr_target)
	95	sig->curr_target = next_thread(tsk);
	96	/*
	97	* Accumulate here the counters for all threads but the
	98	* group leader as they die, so they can be added into
	99	* the process-wide totals when those are taken.
	100	* The group leader stays around as a zombie as long
	101	* as there are other threads. When it gets reaped,
	102	* the exit.c code will add its counts into these totals.
	103	* We won't ever get here for the group leader, since it
	104	* will have been the last reference on the signal_struct.
	105	*/
	106	sig->utime = cputime_add(sig->utime, tsk->utime);
	107	sig->stime = cputime_add(sig->stime, tsk->stime);
	108	sig->min_flt += tsk->min_flt;
	109	sig->maj_flt += tsk->maj_flt;
	110	sig->nvcsw += tsk->nvcsw;
	111	sig->nivcsw += tsk->nivcsw;
	112	sig->sched_time += tsk->sched_time;
	113	sig = NULL; /* Marker for below. */
	114	}
	115
5876700c ON	116	__unhash_process(tsk);
5876700c ON	117
6a14c5c9	118	tsk->signal = NULL;
a7e5328a	119	tsk->sighand = NULL;
6a14c5c9 ON	120	spin_unlock(&sighand->siglock);
	121	rcu_read_unlock();
	122
a7e5328a	123	__cleanup_sighand(sighand);
6a14c5c9 ON	124	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
	125	flush_sigqueue(&tsk->pending);
	126	if (sig) {
	127	flush_sigqueue(&sig->shared_pending);
	128	__cleanup_signal(sig);
	129	}
	130	}
	131
8c7904a0 EB	132	static void delayed_put_task_struct(struct rcu_head *rhp)
	133	{
	134	put_task_struct(container_of(rhp, struct task_struct, rcu));
	135	}
	136
1da177e4 LT	137	void release_task(struct task_struct * p)
	138	{
	139	int zap_leader;
	140	task_t *leader;
	141	struct dentry *proc_dentry;
	142
1f09f974	143	repeat:
1da177e4 LT	144	atomic_dec(&p->user->processes);
	145	spin_lock(&p->proc_lock);
	146	proc_dentry = proc_pid_unhash(p);
	147	write_lock_irq(&tasklist_lock);
1f09f974	148	ptrace_unlink(p);
1da177e4 LT	149	BUG_ON(!list_empty(&p->ptrace_list) \|\| !list_empty(&p->ptrace_children));
1da177e4 LT	150	__exit_signal(p);
35f5cad8	151
1da177e4 LT	152	/*
	153	* If we are the last non-leader member of the thread
	154	* group, and the leader is zombie, then notify the
	155	* group leader's parent process. (if it wants notification.)
	156	*/
	157	zap_leader = 0;
	158	leader = p->group_leader;
	159	if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
	160	BUG_ON(leader->exit_signal == -1);
	161	do_notify_parent(leader, leader->exit_signal);
	162	/*
	163	* If we were the last child thread and the leader has
	164	* exited already, and the leader's parent ignores SIGCHLD,
	165	* then we are the one who should release the leader.
	166	*
	167	* do_notify_parent() will have marked it self-reaping in
	168	* that case.
	169	*/
	170	zap_leader = (leader->exit_signal == -1);
	171	}
	172
	173	sched_exit(p);
	174	write_unlock_irq(&tasklist_lock);
	175	spin_unlock(&p->proc_lock);
	176	proc_pid_flush(proc_dentry);
	177	release_thread(p);
8c7904a0	178	call_rcu(&p->rcu, delayed_put_task_struct);
1da177e4 LT	179
	180	p = leader;
	181	if (unlikely(zap_leader))
	182	goto repeat;
	183	}
	184
1da177e4 LT	185	/*
	186	* This checks not only the pgrp, but falls back on the pid if no
	187	* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
	188	* without this...
	189	*/
	190	int session_of_pgrp(int pgrp)
	191	{
	192	struct task_struct *p;
	193	int sid = -1;
	194
	195	read_lock(&tasklist_lock);
	196	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	197	if (p->signal->session > 0) {
	198	sid = p->signal->session;
	199	goto out;
	200	}
	201	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	202	p = find_task_by_pid(pgrp);
	203	if (p)
	204	sid = p->signal->session;
	205	out:
	206	read_unlock(&tasklist_lock);
	207
	208	return sid;
	209	}
	210
	211	/*
	212	* Determine if a process group is "orphaned", according to the POSIX
	213	* definition in 2.2.2.52. Orphaned process groups are not to be affected
	214	* by terminal-generated stop signals. Newly orphaned process groups are
	215	* to receive a SIGHUP and a SIGCONT.
	216	*
	217	* "I ask you, have you ever known what it is to be an orphan?"
	218	*/
	219	static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
	220	{
	221	struct task_struct *p;
	222	int ret = 1;
	223
	224	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	225	if (p == ignored_task
	226	\|\| p->exit_state
	227	\|\| p->real_parent->pid == 1)
	228	continue;
	229	if (process_group(p->real_parent) != pgrp
	230	&& p->real_parent->signal->session == p->signal->session) {
	231	ret = 0;
	232	break;
	233	}
	234	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	235	return ret; /* (sighing) "Often!" */
	236	}
	237
	238	int is_orphaned_pgrp(int pgrp)
	239	{
	240	int retval;
	241
	242	read_lock(&tasklist_lock);
	243	retval = will_become_orphaned_pgrp(pgrp, NULL);
	244	read_unlock(&tasklist_lock);
	245
	246	return retval;
	247	}
	248
858119e1	249	static int has_stopped_jobs(int pgrp)
1da177e4 LT	250	{
	251	int retval = 0;
	252	struct task_struct *p;
	253
	254	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
	255	if (p->state != TASK_STOPPED)
	256	continue;
	257
	258	/* If p is stopped by a debugger on a signal that won't
	259	stop it, then don't count p as stopped. This isn't
	260	perfect but it's a good approximation. */
	261	if (unlikely (p->ptrace)
	262	&& p->exit_code != SIGSTOP
	263	&& p->exit_code != SIGTSTP
	264	&& p->exit_code != SIGTTOU
	265	&& p->exit_code != SIGTTIN)
	266	continue;
	267
	268	retval = 1;
	269	break;
	270	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
	271	return retval;
	272	}
	273
	274	/**
4dc3b16b	275	* reparent_to_init - Reparent the calling kernel thread to the init task.
1da177e4 LT	276	*
	277	* If a kernel thread is launched as a result of a system call, or if
	278	* it ever exits, it should generally reparent itself to init so that
	279	* it is correctly cleaned up on exit.
	280	*
	281	* The various task state such as scheduling policy and priority may have
	282	* been inherited from a user process, so we reset them to sane values here.
	283	*
	284	* NOTE that reparent_to_init() gives the caller full capabilities.
	285	*/
858119e1	286	static void reparent_to_init(void)
1da177e4 LT	287	{
	288	write_lock_irq(&tasklist_lock);
	289
	290	ptrace_unlink(current);
	291	/* Reparent to init */
9b678ece	292	remove_parent(current);
1da177e4 LT	293	current->parent = child_reaper;
1da177e4 LT	294	current->real_parent = child_reaper;
9b678ece	295	add_parent(current);
1da177e4 LT	296
	297	/* Set the exit signal to SIGCHLD so we signal init on exit */
	298	current->exit_signal = SIGCHLD;
	299
b0a9499c IM	300	if ((current->policy == SCHED_NORMAL \|\|
	301	current->policy == SCHED_BATCH)
	302	&& (task_nice(current) < 0))
1da177e4 LT	303	set_user_nice(current, 0);
	304	/* cpus_allowed? */
	305	/* rt_priority? */
	306	/* signals? */
	307	security_task_reparent_to_init(current);
	308	memcpy(current->signal->rlim, init_task.signal->rlim,
	309	sizeof(current->signal->rlim));
	310	atomic_inc(&(INIT_USER->__count));
	311	write_unlock_irq(&tasklist_lock);
	312	switch_uid(INIT_USER);
	313	}
	314
	315	void __set_special_pids(pid_t session, pid_t pgrp)
	316	{
e19f247a	317	struct task_struct *curr = current->group_leader;
1da177e4 LT	318
	319	if (curr->signal->session != session) {
	320	detach_pid(curr, PIDTYPE_SID);
	321	curr->signal->session = session;
	322	attach_pid(curr, PIDTYPE_SID, session);
	323	}
	324	if (process_group(curr) != pgrp) {
	325	detach_pid(curr, PIDTYPE_PGID);
	326	curr->signal->pgrp = pgrp;
	327	attach_pid(curr, PIDTYPE_PGID, pgrp);
	328	}
	329	}
	330
	331	void set_special_pids(pid_t session, pid_t pgrp)
	332	{
	333	write_lock_irq(&tasklist_lock);
	334	__set_special_pids(session, pgrp);
	335	write_unlock_irq(&tasklist_lock);
	336	}
	337
	338	/*
	339	* Let kernel threads use this to say that they
	340	* allow a certain signal (since daemonize() will
	341	* have disabled all of them by default).
	342	*/
	343	int allow_signal(int sig)
	344	{
7ed20e1a	345	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	346	return -EINVAL;
	347
	348	spin_lock_irq(&current->sighand->siglock);
	349	sigdelset(&current->blocked, sig);
	350	if (!current->mm) {
	351	/* Kernel threads handle their own signals.
	352	Let the signal code know it'll be handled, so
	353	that they don't get converted to SIGKILL or
	354	just silently dropped */
	355	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
	356	}
	357	recalc_sigpending();
	358	spin_unlock_irq(&current->sighand->siglock);
	359	return 0;
	360	}
	361
	362	EXPORT_SYMBOL(allow_signal);
	363
	364	int disallow_signal(int sig)
	365	{
7ed20e1a	366	if (!valid_signal(sig) \|\| sig < 1)
1da177e4 LT	367	return -EINVAL;
	368
	369	spin_lock_irq(&current->sighand->siglock);
	370	sigaddset(&current->blocked, sig);
	371	recalc_sigpending();
	372	spin_unlock_irq(&current->sighand->siglock);
	373	return 0;
	374	}
	375
	376	EXPORT_SYMBOL(disallow_signal);
	377
	378	/*
	379	* Put all the gunge required to become a kernel thread without
	380	* attached user resources in one place where it belongs.
	381	*/
	382
	383	void daemonize(const char *name, ...)
	384	{
	385	va_list args;
	386	struct fs_struct *fs;
	387	sigset_t blocked;
	388
	389	va_start(args, name);
	390	vsnprintf(current->comm, sizeof(current->comm), name, args);
	391	va_end(args);
	392
	393	/*
	394	* If we were started as result of loading a module, close all of the
	395	* user space pages. We don't need them, and if we didn't close them
	396	* they would be locked into memory.
	397	*/
	398	exit_mm(current);
	399
	400	set_special_pids(1, 1);
70522e12	401	mutex_lock(&tty_mutex);
1da177e4	402	current->signal->tty = NULL;
70522e12	403	mutex_unlock(&tty_mutex);
1da177e4 LT	404
	405	/* Block and flush all signals */
	406	sigfillset(&blocked);
	407	sigprocmask(SIG_BLOCK, &blocked, NULL);
	408	flush_signals(current);
	409
	410	/* Become as one with the init task */
	411
	412	exit_fs(current); /* current->fs->count--; */
	413	fs = init_task.fs;
	414	current->fs = fs;
	415	atomic_inc(&fs->count);