[linux.git] / fs / signalfd.c

/*
 *  fs/signalfd.c
 *
 *  Copyright (C) 2003  Linus Torvalds
 *
 *  Mon Mar 5, 2007: Davide Libenzi <[email protected]>
 *      Changed ->read() to return a siginfo strcture instead of signal number.
 *      Fixed locking in ->poll().
 *      Added sighand-detach notification.
 *      Added fd re-use in sys_signalfd() syscall.
 *      Now using anonymous inode source.
 *      Thanks to Oleg Nesterov for useful code review and suggestions.
 *      More comments and suggestions from Arnd Bergmann.
 * Sat May 19, 2007: Davi E. M. Arnaut <[email protected]>
 *      Retrieve multiple signals with one read() call
 */

#include <linux/file.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/list.h>
#include <linux/anon_inodes.h>
#include <linux/signalfd.h>

struct signalfd_ctx {
	struct list_head lnk;
	wait_queue_head_t wqh;
	sigset_t sigmask;
	struct task_struct *tsk;
};

struct signalfd_lockctx {
	struct task_struct *tsk;
	unsigned long flags;
};

/*
 * Tries to acquire the sighand lock. We do not increment the sighand
 * use count, and we do not even pin the task struct, so we need to
 * do it inside an RCU read lock, and we must be prepared for the
 * ctx->tsk going to NULL (in signalfd_deliver()), and for the sighand
 * being detached. We return 0 if the sighand has been detached, or
 * 1 if we were able to pin the sighand lock.
 */
static int signalfd_lock(struct signalfd_ctx *ctx, struct signalfd_lockctx *lk)
{
	struct sighand_struct *sighand = NULL;

	rcu_read_lock();
	lk->tsk = rcu_dereference(ctx->tsk);
	if (likely(lk->tsk != NULL))
		sighand = lock_task_sighand(lk->tsk, &lk->flags);
	rcu_read_unlock();

	if (sighand && !ctx->tsk) {
		unlock_task_sighand(lk->tsk, &lk->flags);
		sighand = NULL;
	}

	return sighand != NULL;
}

static void signalfd_unlock(struct signalfd_lockctx *lk)
{
	unlock_task_sighand(lk->tsk, &lk->flags);
}

/*
 * This must be called with the sighand lock held.
 */
void signalfd_deliver(struct task_struct *tsk, int sig)
{
	struct sighand_struct *sighand = tsk->sighand;
	struct signalfd_ctx *ctx, *tmp;

	BUG_ON(!sig);
	list_for_each_entry_safe(ctx, tmp, &sighand->signalfd_list, lnk) {
		/*
		 * We use a negative signal value as a way to broadcast that the
		 * sighand has been orphaned, so that we can notify all the
		 * listeners about this. Remember the ctx->sigmask is inverted,
		 * so if the user is interested in a signal, that corresponding
		 * bit will be zero.
		 */
		if (sig < 0) {
			if (ctx->tsk == tsk) {
				ctx->tsk = NULL;
				list_del_init(&ctx->lnk);
				wake_up(&ctx->wqh);
			}
		} else {
			if (!sigismember(&ctx->sigmask, sig))
				wake_up(&ctx->wqh);
		}
	}
}

static void signalfd_cleanup(struct signalfd_ctx *ctx)
{
	struct signalfd_lockctx lk;

	/*
	 * This is tricky. If the sighand is gone, we do not need to remove
	 * context from the list, the list itself won't be there anymore.
	 */
	if (signalfd_lock(ctx, &lk)) {
		list_del(&ctx->lnk);
		signalfd_unlock(&lk);
	}
	kfree(ctx);
}

static int signalfd_release(struct inode *inode, struct file *file)
{
	signalfd_cleanup(file->private_data);
	return 0;
}

static unsigned int signalfd_poll(struct file *file, poll_table *wait)
{
	struct signalfd_ctx *ctx = file->private_data;
	unsigned int events = 0;
	struct signalfd_lockctx lk;

	poll_wait(file, &ctx->wqh, wait);

	/*
	 * Let the caller get a POLLIN in this case, ala socket recv() when
	 * the peer disconnects.
	 */
	if (signalfd_lock(ctx, &lk)) {
		if ((lk.tsk == current &&
		     next_signal(&lk.tsk->pending, &ctx->sigmask) > 0) ||
		    next_signal(&lk.tsk->signal->shared_pending,
				&ctx->sigmask) > 0)
			events |= POLLIN;
		signalfd_unlock(&lk);
	} else
		events |= POLLIN;

	return events;
}

/*
 * Copied from copy_siginfo_to_user() in kernel/signal.c
 */
static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
			     siginfo_t const *kinfo)
{
	long err;

	BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);

	/*
	 * Unused memebers should be zero ...
	 */
	err = __clear_user(uinfo, sizeof(*uinfo));

	/*
	 * If you change siginfo_t structure, please be sure
	 * this code is fixed accordingly.
	 */
	err |= __put_user(kinfo->si_signo, &uinfo->signo);
	err |= __put_user(kinfo->si_errno, &uinfo->err);
	err |= __put_user((short)kinfo->si_code, &uinfo->code);
	switch (kinfo->si_code & __SI_MASK) {
	case __SI_KILL:
		err |= __put_user(kinfo->si_pid, &uinfo->pid);
		err |= __put_user(kinfo->si_uid, &uinfo->uid);
		break;
	case __SI_TIMER:
		 err |= __put_user(kinfo->si_tid, &uinfo->tid);
		 err |= __put_user(kinfo->si_overrun, &uinfo->overrun);
		 err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
		break;
	case __SI_POLL:
		err |= __put_user(kinfo->si_band, &uinfo->band);
		err |= __put_user(kinfo->si_fd, &uinfo->fd);
		break;
	case __SI_FAULT:
		err |= __put_user((long)kinfo->si_addr, &uinfo->addr);
#ifdef __ARCH_SI_TRAPNO
		err |= __put_user(kinfo->si_trapno, &uinfo->trapno);
#endif
		break;
	case __SI_CHLD:
		err |= __put_user(kinfo->si_pid, &uinfo->pid);
		err |= __put_user(kinfo->si_uid, &uinfo->uid);
		err |= __put_user(kinfo->si_status, &uinfo->status);
		err |= __put_user(kinfo->si_utime, &uinfo->utime);
		err |= __put_user(kinfo->si_stime, &uinfo->stime);
		break;
	case __SI_RT: /* This is not generated by the kernel as of now. */
	case __SI_MESGQ: /* But this is */
		err |= __put_user(kinfo->si_pid, &uinfo->pid);
		err |= __put_user(kinfo->si_uid, &uinfo->uid);
		err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
		break;
	default: /* this is just in case for now ... */
		err |= __put_user(kinfo->si_pid, &uinfo->pid);
		err |= __put_user(kinfo->si_uid, &uinfo->uid);
		break;
	}

	return err ? -EFAULT: sizeof(*uinfo);
}

static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
				int nonblock)
{
	ssize_t ret;
	struct signalfd_lockctx lk;
	DECLARE_WAITQUEUE(wait, current);

	if (!signalfd_lock(ctx, &lk))
		return 0;

	ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
	switch (ret) {
	case 0:
		if (!nonblock)
			break;
		ret = -EAGAIN;
	default:
		signalfd_unlock(&lk);
		return ret;
	}

	add_wait_queue(&ctx->wqh, &wait);
	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);
		ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
		signalfd_unlock(&lk);
		if (ret != 0)
			break;
		if (signal_pending(current)) {
			ret = -ERESTARTSYS;
			break;
		}
		schedule();
		ret = signalfd_lock(ctx, &lk);
		if (unlikely(!ret)) {
			/*
			 * Let the caller read zero byte, ala socket
			 * recv() when the peer disconnect. This test
			 * must be done before doing a dequeue_signal(),
			 * because if the sighand has been orphaned,
			 * the dequeue_signal() call is going to crash
			 * because ->sighand will be long gone.
			 */
			 break;
		}
	}

	remove_wait_queue(&ctx->wqh, &wait);
	__set_current_state(TASK_RUNNING);

	return ret;
}

/*
 * Returns either the size of a "struct signalfd_siginfo", or zero if the
 * sighand we are attached to, has been orphaned. The "count" parameter
 * must be at least the size of a "struct signalfd_siginfo".
 */
static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
			     loff_t *ppos)
{
	struct signalfd_ctx *ctx = file->private_data;
	struct signalfd_siginfo __user *siginfo;
	int nonblock = file->f_flags & O_NONBLOCK;
	ssize_t ret, total = 0;
	siginfo_t info;

	count /= sizeof(struct signalfd_siginfo);
	if (!count)
		return -EINVAL;

	siginfo = (struct signalfd_siginfo __user *) buf;

	do {
		ret = signalfd_dequeue(ctx, &info, nonblock);
		if (unlikely(ret <= 0))
			break;
		ret = signalfd_copyinfo(siginfo, &info);
		if (ret < 0)
			break;
		siginfo++;
		total += ret;
		nonblock = 1;
	} while (--count);

	return total ? total : ret;
}

static const struct file_operations signalfd_fops = {
	.release	= signalfd_release,
	.poll		= signalfd_poll,
	.read		= signalfd_read,
};

/*
 * Create a file descriptor that is associated with our signal
 * state. We can pass it around to others if we want to, but
 * it will always be _our_ signal state.
 */
asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
{
	int error;
	sigset_t sigmask;
	struct signalfd_ctx *ctx;
	struct sighand_struct *sighand;
	struct file *file;
	struct inode *inode;
	struct signalfd_lockctx lk;

	if (sizemask != sizeof(sigset_t) ||
	    copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
		return error = -EINVAL;
	sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
	signotset(&sigmask);

	if (ufd == -1) {
		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
		if (!ctx)
			return -ENOMEM;

		init_waitqueue_head(&ctx->wqh);
		ctx->sigmask = sigmask;
		ctx->tsk = current;

		sighand = current->sighand;
		/*
		 * Add this fd to the list of signal listeners.
		 */
		spin_lock_irq(&sighand->siglock);
		list_add_tail(&ctx->lnk, &sighand->signalfd_list);
		spin_unlock_irq(&sighand->siglock);

		/*
		 * When we call this, the initialization must be complete, since
		 * anon_inode_getfd() will install the fd.
		 */
		error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]",
					 &signalfd_fops, ctx);
		if (error)
			goto err_fdalloc;
	} else {
		file = fget(ufd);
		if (!file)
			return -EBADF;
		ctx = file->private_data;
		if (file->f_op != &signalfd_fops) {
			fput(file);
			return -EINVAL;
		}
		/*
		 * We need to be prepared of the fact that the sighand this fd
		 * is attached to, has been detched. In that case signalfd_lock()
		 * will return 0, and we'll just skip setting the new mask.
		 */
		if (signalfd_lock(ctx, &lk)) {
			ctx->sigmask = sigmask;
			signalfd_unlock(&lk);
		}
		wake_up(&ctx->wqh);
		fput(file);
	}

	return ufd;

err_fdalloc:
	signalfd_cleanup(ctx);
	return error;
}
Commit	Line	Data
fba2afaa DL	1	/*
	2	* fs/signalfd.c
	3	*
	4	* Copyright (C) 2003 Linus Torvalds
	5	*
	6	* Mon Mar 5, 2007: Davide Libenzi <[email protected]>
	7	* Changed ->read() to return a siginfo strcture instead of signal number.
	8	* Fixed locking in ->poll().
	9	* Added sighand-detach notification.
	10	* Added fd re-use in sys_signalfd() syscall.
	11	* Now using anonymous inode source.
	12	* Thanks to Oleg Nesterov for useful code review and suggestions.
	13	* More comments and suggestions from Arnd Bergmann.
b3762bfc DA	14	* Sat May 19, 2007: Davi E. M. Arnaut <[email protected]>
b3762bfc DA	15	* Retrieve multiple signals with one read() call
fba2afaa DL	16	*/
	17
	18	#include <linux/file.h>
	19	#include <linux/poll.h>
	20	#include <linux/init.h>
	21	#include <linux/fs.h>
	22	#include <linux/sched.h>
	23	#include <linux/kernel.h>
	24	#include <linux/signal.h>
	25	#include <linux/list.h>
	26	#include <linux/anon_inodes.h>
	27	#include <linux/signalfd.h>
	28
	29	struct signalfd_ctx {
	30	struct list_head lnk;
	31	wait_queue_head_t wqh;
	32	sigset_t sigmask;
	33	struct task_struct *tsk;
	34	};
	35
	36	struct signalfd_lockctx {
	37	struct task_struct *tsk;
	38	unsigned long flags;
	39	};
	40
	41	/*
	42	* Tries to acquire the sighand lock. We do not increment the sighand
	43	* use count, and we do not even pin the task struct, so we need to
	44	* do it inside an RCU read lock, and we must be prepared for the
	45	* ctx->tsk going to NULL (in signalfd_deliver()), and for the sighand
	46	* being detached. We return 0 if the sighand has been detached, or
	47	* 1 if we were able to pin the sighand lock.
	48	*/
	49	static int signalfd_lock(struct signalfd_ctx ctx, struct signalfd_lockctx lk)
	50	{
	51	struct sighand_struct *sighand = NULL;
	52
	53	rcu_read_lock();
	54	lk->tsk = rcu_dereference(ctx->tsk);
	55	if (likely(lk->tsk != NULL))
	56	sighand = lock_task_sighand(lk->tsk, &lk->flags);
	57	rcu_read_unlock();
	58
	59	if (sighand && !ctx->tsk) {
	60	unlock_task_sighand(lk->tsk, &lk->flags);
	61	sighand = NULL;
	62	}
	63
	64	return sighand != NULL;
	65	}
	66
	67	static void signalfd_unlock(struct signalfd_lockctx *lk)
	68	{
	69	unlock_task_sighand(lk->tsk, &lk->flags);
	70	}
	71
	72	/*
	73	* This must be called with the sighand lock held.
	74	*/
	75	void signalfd_deliver(struct task_struct *tsk, int sig)
	76	{
	77	struct sighand_struct *sighand = tsk->sighand;
	78	struct signalfd_ctx ctx, tmp;
	79
80	BUG_ON(!sig);
81	list_for_each_entry_safe(ctx, tmp, &sighand->signalfd_list, lnk) {
82	/*
83	* We use a negative signal value as a way to broadcast that the
84	* sighand has been orphaned, so that we can notify all the
85	* listeners about this. Remember the ctx->sigmask is inverted,
86	* so if the user is interested in a signal, that corresponding
87	* bit will be zero.
88	*/
89	if (sig < 0) {
90	if (ctx->tsk == tsk) {
91	ctx->tsk = NULL;
92	list_del_init(&ctx->lnk);
93	wake_up(&ctx->wqh);
94	}
95	} else {
96	if (!sigismember(&ctx->sigmask, sig))
97	wake_up(&ctx->wqh);
98	}
99	}
100	}
101
102	static void signalfd_cleanup(struct signalfd_ctx *ctx)
103	{
104	struct signalfd_lockctx lk;
105
106	/*
107	* This is tricky. If the sighand is gone, we do not need to remove
108	* context from the list, the list itself won't be there anymore.
109	*/
110	if (signalfd_lock(ctx, &lk)) {
111	list_del(&ctx->lnk);
112	signalfd_unlock(&lk);
113	}
114	kfree(ctx);
115	}
116
117	static int signalfd_release(struct inode inode, struct file file)
118	{
119	signalfd_cleanup(file->private_data);
120	return 0;
121	}
122
123	static unsigned int signalfd_poll(struct file file, poll_table wait)
124	{
125	struct signalfd_ctx *ctx = file->private_data;
126	unsigned int events = 0;
127	struct signalfd_lockctx lk;
128
129	poll_wait(file, &ctx->wqh, wait);
130
131	/*
132	* Let the caller get a POLLIN in this case, ala socket recv() when
133	* the peer disconnects.
134	*/
135	if (signalfd_lock(ctx, &lk)) {
f8738c5c DL	136	if ((lk.tsk == current &&
f8738c5c DL	137	next_signal(&lk.tsk->pending, &ctx->sigmask) > 0) \|\|
fba2afaa DL	138	next_signal(&lk.tsk->signal->shared_pending,
	139	&ctx->sigmask) > 0)
	140	events \|= POLLIN;
	141	signalfd_unlock(&lk);
	142	} else
	143	events \|= POLLIN;
	144
	145	return events;
	146	}
	147
	148	/*
	149	* Copied from copy_siginfo_to_user() in kernel/signal.c
	150	*/
	151	static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
	152	siginfo_t const *kinfo)
	153	{
	154	long err;
	155
	156	BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
	157
	158	/*
	159	* Unused memebers should be zero ...
	160	*/
	161	err = __clear_user(uinfo, sizeof(*uinfo));
	162
	163	/*
	164	* If you change siginfo_t structure, please be sure
	165	* this code is fixed accordingly.
	166	*/
	167	err \|= __put_user(kinfo->si_signo, &uinfo->signo);
	168	err \|= __put_user(kinfo->si_errno, &uinfo->err);
	169	err \|= __put_user((short)kinfo->si_code, &uinfo->code);
	170	switch (kinfo->si_code & __SI_MASK) {
	171	case __SI_KILL:
	172	err \|= __put_user(kinfo->si_pid, &uinfo->pid);
	173	err \|= __put_user(kinfo->si_uid, &uinfo->uid);
	174	break;
	175	case __SI_TIMER:
	176	err \|= __put_user(kinfo->si_tid, &uinfo->tid);
	177	err \|= __put_user(kinfo->si_overrun, &uinfo->overrun);
	178	err \|= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
	179	break;
	180	case __SI_POLL:
	181	err \|= __put_user(kinfo->si_band, &uinfo->band);
	182	err \|= __put_user(kinfo->si_fd, &uinfo->fd);
	183	break;
	184	case __SI_FAULT:
	185	err \|= __put_user((long)kinfo->si_addr, &uinfo->addr);
	186	#ifdef __ARCH_SI_TRAPNO
	187	err \|= __put_user(kinfo->si_trapno, &uinfo->trapno);
	188	#endif
	189	break;
	190	case __SI_CHLD:
	191	err \|= __put_user(kinfo->si_pid, &uinfo->pid);
	192	err \|= __put_user(kinfo->si_uid, &uinfo->uid);
	193	err \|= __put_user(kinfo->si_status, &uinfo->status);
	194	err \|= __put_user(kinfo->si_utime, &uinfo->utime);
	195	err \|= __put_user(kinfo->si_stime, &uinfo->stime);
	196	break;
	197	case __SI_RT: /* This is not generated by the kernel as of now. */
	198	case __SI_MESGQ: /* But this is */
	199	err \|= __put_user(kinfo->si_pid, &uinfo->pid);
	200	err \|= __put_user(kinfo->si_uid, &uinfo->uid);
	201	err \|= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
202	break;
203	default: /* this is just in case for now ... */
204	err \|= __put_user(kinfo->si_pid, &uinfo->pid);
205	err \|= __put_user(kinfo->si_uid, &uinfo->uid);
206	break;
207	}
208
209	return err ? -EFAULT: sizeof(*uinfo);
210	}
211
b3762bfc DA	212	static ssize_t signalfd_dequeue(struct signalfd_ctx ctx, siginfo_t info,
	213	int nonblock)
	214	{
	215	ssize_t ret;
	216	struct signalfd_lockctx lk;
	217	DECLARE_WAITQUEUE(wait, current);
	218
	219	if (!signalfd_lock(ctx, &lk))
	220	return 0;
	221
	222	ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
	223	switch (ret) {
	224	case 0:
	225	if (!nonblock)
	226	break;
	227	ret = -EAGAIN;
	228	default:
	229	signalfd_unlock(&lk);
	230	return ret;
	231	}
	232
	233	add_wait_queue(&ctx->wqh, &wait);
	234	for (;;) {
	235	set_current_state(TASK_INTERRUPTIBLE);
	236	ret = dequeue_signal(lk.tsk, &ctx->sigmask, info);
	237	signalfd_unlock(&lk);
	238	if (ret != 0)
	239	break;
	240	if (signal_pending(current)) {
	241	ret = -ERESTARTSYS;
	242	break;
	243	}
	244	schedule();
	245	ret = signalfd_lock(ctx, &lk);
	246	if (unlikely(!ret)) {
	247	/*
	248	* Let the caller read zero byte, ala socket
	249	* recv() when the peer disconnect. This test
	250	* must be done before doing a dequeue_signal(),
	251	* because if the sighand has been orphaned,
	252	* the dequeue_signal() call is going to crash
	253	* because ->sighand will be long gone.
	254	*/
	255	break;
	256	}
	257	}
	258
	259	remove_wait_queue(&ctx->wqh, &wait);
	260	__set_current_state(TASK_RUNNING);
	261
	262	return ret;
	263	}
	264
fba2afaa DL	265	/*
	266	* Returns either the size of a "struct signalfd_siginfo", or zero if the
	267	* sighand we are attached to, has been orphaned. The "count" parameter
	268	* must be at least the size of a "struct signalfd_siginfo".
	269	*/
	270	static ssize_t signalfd_read(struct file file, char __user buf, size_t count,
	271	loff_t *ppos)
	272	{
	273	struct signalfd_ctx *ctx = file->private_data;
b3762bfc DA	274	struct signalfd_siginfo __user *siginfo;
	275	int nonblock = file->f_flags & O_NONBLOCK;
	276	ssize_t ret, total = 0;
fba2afaa	277	siginfo_t info;
fba2afaa	278
b3762bfc DA	279	count /= sizeof(struct signalfd_siginfo);
b3762bfc DA	280	if (!count)
fba2afaa	281	return -EINVAL;
fba2afaa	282
b3762bfc DA	283	siginfo = (struct signalfd_siginfo __user *) buf;
	284
	285	do {
	286	ret = signalfd_dequeue(ctx, &info, nonblock);
	287	if (unlikely(ret <= 0))
	288	break;
	289	ret = signalfd_copyinfo(siginfo, &info);
	290	if (ret < 0)
	291	break;
	292	siginfo++;
	293	total += ret;
	294	nonblock = 1;
	295	} while (--count);
	296
	297	return total ? total : ret;
fba2afaa DL	298	}
	299
	300	static const struct file_operations signalfd_fops = {
	301	.release = signalfd_release,
	302	.poll = signalfd_poll,
	303	.read = signalfd_read,
	304	};
	305
	306	/*
	307	* Create a file descriptor that is associated with our signal
	308	* state. We can pass it around to others if we want to, but
	309	* it will always be _our_ signal state.
	310	*/
	311	asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
	312	{
	313	int error;
	314	sigset_t sigmask;
	315	struct signalfd_ctx *ctx;
	316	struct sighand_struct *sighand;
	317	struct file *file;
	318	struct inode *inode;
	319	struct signalfd_lockctx lk;
	320
	321	if (sizemask != sizeof(sigset_t) \|\|
	322	copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
	323	return error = -EINVAL;
	324	sigdelsetmask(&sigmask, sigmask(SIGKILL) \| sigmask(SIGSTOP));
	325	signotset(&sigmask);
	326
	327	if (ufd == -1) {
	328	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
	329	if (!ctx)
	330	return -ENOMEM;
	331
	332	init_waitqueue_head(&ctx->wqh);
	333	ctx->sigmask = sigmask;
	334	ctx->tsk = current;
	335
	336	sighand = current->sighand;
	337	/*
	338	* Add this fd to the list of signal listeners.
	339	*/
	340	spin_lock_irq(&sighand->siglock);
	341	list_add_tail(&ctx->lnk, &sighand->signalfd_list);
	342	spin_unlock_irq(&sighand->siglock);
	343
	344	/*
	345	* When we call this, the initialization must be complete, since
	346	* anon_inode_getfd() will install the fd.
	347	*/
	348	error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]",
	349	&signalfd_fops, ctx);
	350	if (error)
	351	goto err_fdalloc;
	352	} else {
	353	file = fget(ufd);
	354	if (!file)
	355	return -EBADF;
	356	ctx = file->private_data;
	357	if (file->f_op != &signalfd_fops) {
	358	fput(file);
	359	return -EINVAL;
	360	}
	361	/*
362	* We need to be prepared of the fact that the sighand this fd
363	* is attached to, has been detched. In that case signalfd_lock()
364	* will return 0, and we'll just skip setting the new mask.
365	*/
366	if (signalfd_lock(ctx, &lk)) {
367	ctx->sigmask = sigmask;
368	signalfd_unlock(&lk);
369	}
370	wake_up(&ctx->wqh);
371	fput(file);
372	}
373
374	return ufd;
375
376	err_fdalloc:
377	signalfd_cleanup(ctx);
378	return error;
379	}
380