[linux-block.git] / fs / timerfd.c

/*
 *  fs/timerfd.c
 *
 *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
 *
 *
 *  Thanks to Thomas Gleixner for code reviews and useful comments.
 *
 */

#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/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/time.h>
#include <linux/hrtimer.h>
#include <linux/anon_inodes.h>
#include <linux/timerfd.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>

struct timerfd_ctx {
	struct hrtimer tmr;
	ktime_t tintv;
	ktime_t moffs;
	wait_queue_head_t wqh;
	u64 ticks;
	int expired;
	int clockid;
	struct rcu_head rcu;
	struct list_head clist;
	bool might_cancel;
};

static LIST_HEAD(cancel_list);
static DEFINE_SPINLOCK(cancel_lock);

/*
 * This gets called when the timer event triggers. We set the "expired"
 * flag, but we do not re-arm the timer (in case it's necessary,
 * tintv.tv64 != 0) until the timer is accessed.
 */
static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
{
	struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
	unsigned long flags;

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	ctx->expired = 1;
	ctx->ticks++;
	wake_up_locked(&ctx->wqh);
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return HRTIMER_NORESTART;
}

/*
 * Called when the clock was set to cancel the timers in the cancel
 * list.
 */
void timerfd_clock_was_set(void)
{
	ktime_t moffs = ktime_get_monotonic_offset();
	struct timerfd_ctx *ctx;
	unsigned long flags;

	rcu_read_lock();
	list_for_each_entry_rcu(ctx, &cancel_list, clist) {
		if (!ctx->might_cancel)
			continue;
		spin_lock_irqsave(&ctx->wqh.lock, flags);
		if (ctx->moffs.tv64 != moffs.tv64) {
			ctx->moffs.tv64 = KTIME_MAX;
			wake_up_locked(&ctx->wqh);
		}
		spin_unlock_irqrestore(&ctx->wqh.lock, flags);
	}
	rcu_read_unlock();
}

static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
{
	if (ctx->might_cancel) {
		ctx->might_cancel = false;
		spin_lock(&cancel_lock);
		list_del_rcu(&ctx->clist);
		spin_unlock(&cancel_lock);
	}
}

static bool timerfd_canceled(struct timerfd_ctx *ctx)
{
	if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX)
		return false;
	ctx->moffs = ktime_get_monotonic_offset();
	return true;
}

static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
{
	if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) &&
	    (flags & TFD_TIMER_CANCEL_ON_SET)) {
		if (!ctx->might_cancel) {
			ctx->might_cancel = true;
			spin_lock(&cancel_lock);
			list_add_rcu(&ctx->clist, &cancel_list);
			spin_unlock(&cancel_lock);
		}
	} else if (ctx->might_cancel) {
		timerfd_remove_cancel(ctx);
	}
}

static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
{
	ktime_t remaining;

	remaining = hrtimer_expires_remaining(&ctx->tmr);
	return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
}

static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
			 const struct itimerspec *ktmr)
{
	enum hrtimer_mode htmode;
	ktime_t texp;
	int clockid = ctx->clockid;

	htmode = (flags & TFD_TIMER_ABSTIME) ?
		HRTIMER_MODE_ABS: HRTIMER_MODE_REL;

	texp = timespec_to_ktime(ktmr->it_value);
	ctx->expired = 0;
	ctx->ticks = 0;
	ctx->tintv = timespec_to_ktime(ktmr->it_interval);
	hrtimer_init(&ctx->tmr, clockid, htmode);
	hrtimer_set_expires(&ctx->tmr, texp);
	ctx->tmr.function = timerfd_tmrproc;
	if (texp.tv64 != 0) {
		hrtimer_start(&ctx->tmr, texp, htmode);
		if (timerfd_canceled(ctx))
			return -ECANCELED;
	}
	return 0;
}

static int timerfd_release(struct inode *inode, struct file *file)
{
	struct timerfd_ctx *ctx = file->private_data;

	timerfd_remove_cancel(ctx);
	hrtimer_cancel(&ctx->tmr);
	kfree_rcu(ctx, rcu);
	return 0;
}

static unsigned int timerfd_poll(struct file *file, poll_table *wait)
{
	struct timerfd_ctx *ctx = file->private_data;
	unsigned int events = 0;
	unsigned long flags;

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

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ctx->ticks)
		events |= POLLIN;
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return events;
}

static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
			    loff_t *ppos)
{
	struct timerfd_ctx *ctx = file->private_data;
	ssize_t res;
	u64 ticks = 0;

	if (count < sizeof(ticks))
		return -EINVAL;
	spin_lock_irq(&ctx->wqh.lock);
	if (file->f_flags & O_NONBLOCK)
		res = -EAGAIN;
	else
		res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);

	/*
	 * If clock has changed, we do not care about the
	 * ticks and we do not rearm the timer. Userspace must
	 * reevaluate anyway.
	 */
	if (timerfd_canceled(ctx)) {
		ctx->ticks = 0;
		ctx->expired = 0;
		res = -ECANCELED;
	}

	if (ctx->ticks) {
		ticks = ctx->ticks;

		if (ctx->expired && ctx->tintv.tv64) {
			/*
			 * If tintv.tv64 != 0, this is a periodic timer that
			 * needs to be re-armed. We avoid doing it in the timer
			 * callback to avoid DoS attacks specifying a very
			 * short timer period.
			 */
			ticks += hrtimer_forward_now(&ctx->tmr,
						     ctx->tintv) - 1;
			hrtimer_restart(&ctx->tmr);
		}
		ctx->expired = 0;
		ctx->ticks = 0;
	}
	spin_unlock_irq(&ctx->wqh.lock);
	if (ticks)
		res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
	return res;
}

static const struct file_operations timerfd_fops = {
	.release	= timerfd_release,
	.poll		= timerfd_poll,
	.read		= timerfd_read,
	.llseek		= noop_llseek,
};

static struct file *timerfd_fget(int fd)
{
	struct file *file;

	file = fget(fd);
	if (!file)
		return ERR_PTR(-EBADF);
	if (file->f_op != &timerfd_fops) {
		fput(file);
		return ERR_PTR(-EINVAL);
	}

	return file;
}

SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
{
	int ufd;
	struct timerfd_ctx *ctx;

	/* Check the TFD_* constants for consistency.  */
	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
	BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);

	if ((flags & ~TFD_CREATE_FLAGS) ||
	    (clockid != CLOCK_MONOTONIC &&
	     clockid != CLOCK_REALTIME))
		return -EINVAL;

	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;

	init_waitqueue_head(&ctx->wqh);
	ctx->clockid = clockid;
	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
	ctx->moffs = ktime_get_monotonic_offset();

	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
	if (ufd < 0)
		kfree(ctx);

	return ufd;
}

SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
		const struct itimerspec __user *, utmr,
		struct itimerspec __user *, otmr)
{
	struct file *file;
	struct timerfd_ctx *ctx;
	struct itimerspec ktmr, kotmr;
	int ret;

	if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
		return -EFAULT;

	if ((flags & ~TFD_SETTIME_FLAGS) ||
	    !timespec_valid(&ktmr.it_value) ||
	    !timespec_valid(&ktmr.it_interval))
		return -EINVAL;

	file = timerfd_fget(ufd);
	if (IS_ERR(file))
		return PTR_ERR(file);
	ctx = file->private_data;

	timerfd_setup_cancel(ctx, flags);

	/*
	 * We need to stop the existing timer before reprogramming
	 * it to the new values.
	 */
	for (;;) {
		spin_lock_irq(&ctx->wqh.lock);
		if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
			break;
		spin_unlock_irq(&ctx->wqh.lock);
		cpu_relax();
	}

	/*
	 * If the timer is expired and it's periodic, we need to advance it
	 * because the caller may want to know the previous expiration time.
	 * We do not update "ticks" and "expired" since the timer will be
	 * re-programmed again in the following timerfd_setup() call.
	 */
	if (ctx->expired && ctx->tintv.tv64)
		hrtimer_forward_now(&ctx->tmr, ctx->tintv);

	kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	kotmr.it_interval = ktime_to_timespec(ctx->tintv);

	/*
	 * Re-program the timer to the new value ...
	 */
	ret = timerfd_setup(ctx, flags, &ktmr);

	spin_unlock_irq(&ctx->wqh.lock);
	fput(file);
	if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
		return -EFAULT;

	return ret;
}

SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
{
	struct file *file;
	struct timerfd_ctx *ctx;
	struct itimerspec kotmr;

	file = timerfd_fget(ufd);
	if (IS_ERR(file))
		return PTR_ERR(file);
	ctx = file->private_data;

	spin_lock_irq(&ctx->wqh.lock);
	if (ctx->expired && ctx->tintv.tv64) {
		ctx->expired = 0;
		ctx->ticks +=
			hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
		hrtimer_restart(&ctx->tmr);
	}
	kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	kotmr.it_interval = ktime_to_timespec(ctx->tintv);
	spin_unlock_irq(&ctx->wqh.lock);
	fput(file);

	return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
}
Commit	Line	Data
b215e283 DL	1	/*
	2	* fs/timerfd.c
	3	*
	4	* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
	5	*
	6	*
	7	* Thanks to Thomas Gleixner for code reviews and useful comments.
	8	*
	9	*/
	10
	11	#include <linux/file.h>
	12	#include <linux/poll.h>
	13	#include <linux/init.h>
	14	#include <linux/fs.h>
	15	#include <linux/sched.h>
	16	#include <linux/kernel.h>
5a0e3ad6	17	#include <linux/slab.h>
b215e283 DL	18	#include <linux/list.h>
	19	#include <linux/spinlock.h>
	20	#include <linux/time.h>
	21	#include <linux/hrtimer.h>
	22	#include <linux/anon_inodes.h>
	23	#include <linux/timerfd.h>
45cc2b96	24	#include <linux/syscalls.h>
9ec26907	25	#include <linux/rcupdate.h>
b215e283 DL	26
	27	struct timerfd_ctx {
	28	struct hrtimer tmr;
	29	ktime_t tintv;
99ee5315	30	ktime_t moffs;
b215e283	31	wait_queue_head_t wqh;
4d672e7a	32	u64 ticks;
b215e283	33	int expired;
4d672e7a	34	int clockid;
9ec26907 TG	35	struct rcu_head rcu;
9ec26907 TG	36	struct list_head clist;
99ee5315	37	bool might_cancel;
b215e283 DL	38	};
b215e283 DL	39
9ec26907 TG	40	static LIST_HEAD(cancel_list);
	41	static DEFINE_SPINLOCK(cancel_lock);
	42
b215e283 DL	43	/*
	44	* This gets called when the timer event triggers. We set the "expired"
	45	* flag, but we do not re-arm the timer (in case it's necessary,
4d672e7a	46	* tintv.tv64 != 0) until the timer is accessed.
b215e283 DL	47	*/
	48	static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
	49	{
	50	struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
	51	unsigned long flags;
	52
18963c01	53	spin_lock_irqsave(&ctx->wqh.lock, flags);
b215e283	54	ctx->expired = 1;
4d672e7a	55	ctx->ticks++;
b215e283	56	wake_up_locked(&ctx->wqh);
18963c01	57	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
b215e283 DL	58
	59	return HRTIMER_NORESTART;
	60	}
	61
9ec26907 TG	62	/*
	63	* Called when the clock was set to cancel the timers in the cancel
	64	* list.
	65	*/
	66	void timerfd_clock_was_set(void)
4d672e7a	67	{
9ec26907 TG	68	ktime_t moffs = ktime_get_monotonic_offset();
	69	struct timerfd_ctx *ctx;
	70	unsigned long flags;
4d672e7a	71
9ec26907 TG	72	rcu_read_lock();
	73	list_for_each_entry_rcu(ctx, &cancel_list, clist) {
	74	if (!ctx->might_cancel)
	75	continue;
	76	spin_lock_irqsave(&ctx->wqh.lock, flags);
	77	if (ctx->moffs.tv64 != moffs.tv64) {
	78	ctx->moffs.tv64 = KTIME_MAX;
	79	wake_up_locked(&ctx->wqh);
	80	}
	81	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
	82	}
	83	rcu_read_unlock();
4d672e7a DL	84	}
4d672e7a DL	85
9ec26907	86	static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
99ee5315	87	{
9ec26907 TG	88	if (ctx->might_cancel) {
	89	ctx->might_cancel = false;
	90	spin_lock(&cancel_lock);
	91	list_del_rcu(&ctx->clist);
	92	spin_unlock(&cancel_lock);
	93	}
	94	}
99ee5315	95
9ec26907 TG	96	static bool timerfd_canceled(struct timerfd_ctx *ctx)
	97	{
	98	if (!ctx->might_cancel \|\| ctx->moffs.tv64 != KTIME_MAX)
99ee5315	99	return false;
9ec26907 TG	100	ctx->moffs = ktime_get_monotonic_offset();
	101	return true;
	102	}
99ee5315	103
9ec26907 TG	104	static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
	105	{
	106	if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) &&
	107	(flags & TFD_TIMER_CANCEL_ON_SET)) {
	108	if (!ctx->might_cancel) {
	109	ctx->might_cancel = true;
	110	spin_lock(&cancel_lock);
	111	list_add_rcu(&ctx->clist, &cancel_list);
	112	spin_unlock(&cancel_lock);
	113	}
	114	} else if (ctx->might_cancel) {
	115	timerfd_remove_cancel(ctx);
	116	}
	117	}
99ee5315	118
9ec26907 TG	119	static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
	120	{
	121	ktime_t remaining;
99ee5315	122
9ec26907 TG	123	remaining = hrtimer_expires_remaining(&ctx->tmr);
9ec26907 TG	124	return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
99ee5315 TG	125	}
	126
	127	static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
	128	const struct itimerspec *ktmr)
b215e283 DL	129	{
	130	enum hrtimer_mode htmode;
	131	ktime_t texp;
99ee5315	132	int clockid = ctx->clockid;
b215e283 DL	133
	134	htmode = (flags & TFD_TIMER_ABSTIME) ?
	135	HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
	136
	137	texp = timespec_to_ktime(ktmr->it_value);
	138	ctx->expired = 0;
4d672e7a	139	ctx->ticks = 0;
b215e283	140	ctx->tintv = timespec_to_ktime(ktmr->it_interval);
99ee5315	141	hrtimer_init(&ctx->tmr, clockid, htmode);
76369470	142	hrtimer_set_expires(&ctx->tmr, texp);
b215e283	143	ctx->tmr.function = timerfd_tmrproc;
99ee5315	144	if (texp.tv64 != 0) {
b215e283	145	hrtimer_start(&ctx->tmr, texp, htmode);
99ee5315 TG	146	if (timerfd_canceled(ctx))
	147	return -ECANCELED;
	148	}
	149	return 0;
b215e283 DL	150	}
	151
	152	static int timerfd_release(struct inode inode, struct file file)
	153	{
	154	struct timerfd_ctx *ctx = file->private_data;
	155
9ec26907	156	timerfd_remove_cancel(ctx);
b215e283	157	hrtimer_cancel(&ctx->tmr);
9ec26907	158	kfree_rcu(ctx, rcu);
b215e283 DL	159	return 0;
	160	}
	161
	162	static unsigned int timerfd_poll(struct file file, poll_table wait)
	163	{
	164	struct timerfd_ctx *ctx = file->private_data;
	165	unsigned int events = 0;
	166	unsigned long flags;
	167
	168	poll_wait(file, &ctx->wqh, wait);
	169
18963c01	170	spin_lock_irqsave(&ctx->wqh.lock, flags);
4d672e7a	171	if (ctx->ticks)
b215e283	172	events \|= POLLIN;
18963c01	173	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
b215e283 DL	174
	175	return events;
	176	}
	177
	178	static ssize_t timerfd_read(struct file file, char __user buf, size_t count,
	179	loff_t *ppos)
	180	{
	181	struct timerfd_ctx *ctx = file->private_data;
	182	ssize_t res;
09828402	183	u64 ticks = 0;
b215e283 DL	184
	185	if (count < sizeof(ticks))
	186	return -EINVAL;
18963c01	187	spin_lock_irq(&ctx->wqh.lock);
8120a8aa MN	188	if (file->f_flags & O_NONBLOCK)
	189	res = -EAGAIN;
	190	else
	191	res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
99ee5315	192
9ec26907 TG	193	/*
	194	* If clock has changed, we do not care about the
	195	* ticks and we do not rearm the timer. Userspace must
	196	* reevaluate anyway.
	197	*/
	198	if (timerfd_canceled(ctx)) {
	199	ctx->ticks = 0;
	200	ctx->expired = 0;
	201	res = -ECANCELED;
	202	}
	203
4d672e7a DL	204	if (ctx->ticks) {
4d672e7a DL	205	ticks = ctx->ticks;
99ee5315	206
4d672e7a	207	if (ctx->expired && ctx->tintv.tv64) {
b215e283 DL	208	/*
	209	* If tintv.tv64 != 0, this is a periodic timer that
	210	* needs to be re-armed. We avoid doing it in the timer
	211	* callback to avoid DoS attacks specifying a very
	212	* short timer period.
	213	*/
4d672e7a DL	214	ticks += hrtimer_forward_now(&ctx->tmr,
4d672e7a DL	215	ctx->tintv) - 1;
b215e283	216	hrtimer_restart(&ctx->tmr);
4d672e7a DL	217	}
	218	ctx->expired = 0;
	219	ctx->ticks = 0;
b215e283	220	}
18963c01	221	spin_unlock_irq(&ctx->wqh.lock);
b215e283	222	if (ticks)
09828402	223	res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
b215e283 DL	224	return res;
	225	}
	226
	227	static const struct file_operations timerfd_fops = {
	228	.release = timerfd_release,
	229	.poll = timerfd_poll,
	230	.read = timerfd_read,
6038f373	231	.llseek = noop_llseek,
b215e283 DL	232	};
b215e283 DL	233
4d672e7a DL	234	static struct file *timerfd_fget(int fd)
	235	{
	236	struct file *file;
	237
	238	file = fget(fd);
	239	if (!file)
	240	return ERR_PTR(-EBADF);
	241	if (file->f_op != &timerfd_fops) {
	242	fput(file);
	243	return ERR_PTR(-EINVAL);
	244	}
	245
	246	return file;
	247	}
	248
836f92ad	249	SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
b215e283	250	{
2030a42c	251	int ufd;
b215e283	252	struct timerfd_ctx *ctx;
b215e283	253
e38b36f3 UD	254	/* Check the TFD_* constants for consistency. */
	255	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
	256	BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
	257
610d18f4 DL	258	if ((flags & ~TFD_CREATE_FLAGS) \|\|
	259	(clockid != CLOCK_MONOTONIC &&
	260	clockid != CLOCK_REALTIME))
b215e283	261	return -EINVAL;
4d672e7a DL	262
	263	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
	264	if (!ctx)
	265	return -ENOMEM;
	266
	267	init_waitqueue_head(&ctx->wqh);
	268	ctx->clockid = clockid;
	269	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
99ee5315	270	ctx->moffs = ktime_get_monotonic_offset();
4d672e7a	271
11fcb6c1	272	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
628ff7c1	273	O_RDWR \| (flags & TFD_SHARED_FCNTL_FLAGS));
2030a42c	274	if (ufd < 0)
4d672e7a	275	kfree(ctx);
4d672e7a DL	276
	277	return ufd;
	278	}
	279
836f92ad HC	280	SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
	281	const struct itimerspec __user *, utmr,
	282	struct itimerspec __user *, otmr)
4d672e7a DL	283	{
	284	struct file *file;
	285	struct timerfd_ctx *ctx;
	286	struct itimerspec ktmr, kotmr;
99ee5315	287	int ret;
4d672e7a DL	288
	289	if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
	290	return -EFAULT;
	291
610d18f4 DL	292	if ((flags & ~TFD_SETTIME_FLAGS) \|\|
610d18f4 DL	293	!timespec_valid(&ktmr.it_value) \|\|
b215e283 DL	294	!timespec_valid(&ktmr.it_interval))
	295	return -EINVAL;
	296
4d672e7a DL	297	file = timerfd_fget(ufd);
	298	if (IS_ERR(file))
	299	return PTR_ERR(file);
	300	ctx = file->private_data;
b215e283	301
9ec26907 TG	302	timerfd_setup_cancel(ctx, flags);
9ec26907 TG	303
4d672e7a DL	304	/*
	305	* We need to stop the existing timer before reprogramming
	306	* it to the new values.
	307	*/
	308	for (;;) {
	309	spin_lock_irq(&ctx->wqh.lock);
	310	if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
	311	break;
18963c01	312	spin_unlock_irq(&ctx->wqh.lock);
4d672e7a	313	cpu_relax();
b215e283 DL	314	}
b215e283 DL	315
4d672e7a DL	316	/*
	317	* If the timer is expired and it's periodic, we need to advance it
	318	* because the caller may want to know the previous expiration time.
	319	* We do not update "ticks" and "expired" since the timer will be
	320	* re-programmed again in the following timerfd_setup() call.
	321	*/
	322	if (ctx->expired && ctx->tintv.tv64)
	323	hrtimer_forward_now(&ctx->tmr, ctx->tintv);
b215e283	324
4d672e7a DL	325	kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	326	kotmr.it_interval = ktime_to_timespec(ctx->tintv);
	327
	328	/*
	329	* Re-program the timer to the new value ...
	330	*/
99ee5315	331	ret = timerfd_setup(ctx, flags, &ktmr);
4d672e7a DL	332
	333	spin_unlock_irq(&ctx->wqh.lock);
	334	fput(file);
	335	if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
	336	return -EFAULT;
	337
99ee5315	338	return ret;
4d672e7a DL	339	}
4d672e7a DL	340
d4e82042	341	SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
4d672e7a DL	342	{
	343	struct file *file;
	344	struct timerfd_ctx *ctx;
	345	struct itimerspec kotmr;
	346
	347	file = timerfd_fget(ufd);
	348	if (IS_ERR(file))
	349	return PTR_ERR(file);
	350	ctx = file->private_data;
	351
	352	spin_lock_irq(&ctx->wqh.lock);
	353	if (ctx->expired && ctx->tintv.tv64) {
	354	ctx->expired = 0;
	355	ctx->ticks +=
	356	hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
	357	hrtimer_restart(&ctx->tmr);
	358	}
	359	kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	360	kotmr.it_interval = ktime_to_timespec(ctx->tintv);
	361	spin_unlock_irq(&ctx->wqh.lock);
	362	fput(file);
	363
	364	return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
b215e283 DL	365	}
b215e283 DL	366