fs/timerfd.c - arm/linux-arm64-legacy - Git at Google

 /*
  *  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/compat.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. This will wake up processes waiting on these timers. The
  * wake-up requires ctx->ticks to be non zero, therefore we increment
  * it before calling wake_up_locked().
  */
 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;
 			ctx->ticks++;
 			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 int timerfd_fget(int fd, struct fd *p)
 {
 	struct fd f = fdget(fd);
 	if (!f.file)
 		return -EBADF;
 	if (f.file->f_op != &timerfd_fops) {
 		fdput(f);
 		return -EINVAL;
 	}
 	*p = f;
 	return 0;
 }

 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;
 }

 static int do_timerfd_settime(int ufd, int flags,
 		const struct itimerspec *new,
 		struct itimerspec *old)
 {
 	struct fd f;
 	struct timerfd_ctx *ctx;
 	int ret;

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

 	ret = timerfd_fget(ufd, &f);
 	if (ret)
 		return ret;
 	ctx = f.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);

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

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

 	spin_unlock_irq(&ctx->wqh.lock);
 	fdput(f);
 	return ret;
 }

 static int do_timerfd_gettime(int ufd, struct itimerspec *t)
 {
 	struct fd f;
 	struct timerfd_ctx *ctx;
 	int ret = timerfd_fget(ufd, &f);
 	if (ret)
 		return ret;
 	ctx = f.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);
 	}
 	t->it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
 	t->it_interval = ktime_to_timespec(ctx->tintv);
 	spin_unlock_irq(&ctx->wqh.lock);
 	fdput(f);
 	return 0;
 }

 SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
 		const struct itimerspec __user *, utmr,
 		struct itimerspec __user *, otmr)
 {
 	struct itimerspec new, old;
 	int ret;

 	if (copy_from_user(&new, utmr, sizeof(new)))
 		return -EFAULT;
 	ret = do_timerfd_settime(ufd, flags, &new, &old);
 	if (ret)
 		return ret;
 	if (otmr && copy_to_user(otmr, &old, sizeof(old)))
 		return -EFAULT;

 	return ret;
 }

 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
 {
 	struct itimerspec kotmr;
 	int ret = do_timerfd_gettime(ufd, &kotmr);
 	if (ret)
 		return ret;
 	return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
 }

 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
 		const struct compat_itimerspec __user *, utmr,
 		struct compat_itimerspec __user *, otmr)
 {
 	struct itimerspec new, old;
 	int ret;

 	if (get_compat_itimerspec(&new, utmr))
 		return -EFAULT;
 	ret = do_timerfd_settime(ufd, flags, &new, &old);
 	if (ret)
 		return ret;
 	if (otmr && put_compat_itimerspec(otmr, &old))
 		return -EFAULT;
 	return ret;
 }

 COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
 		struct compat_itimerspec __user *, otmr)
 {
 	struct itimerspec kotmr;
 	int ret = do_timerfd_gettime(ufd, &kotmr);
 	if (ret)
 		return ret;
 	return put_compat_itimerspec(otmr, &kotmr) ? -EFAULT: 0;
 }
 #endif
	/*
	* 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/compat.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. This will wake up processes waiting on these timers. The
	* wake-up requires ctx->ticks to be non zero, therefore we increment
	* it before calling wake_up_locked().
	*/
	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;
	ctx->ticks++;
	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 int timerfd_fget(int fd, struct fd *p)
	{
	struct fd f = fdget(fd);
	if (!f.file)
	return -EBADF;
	if (f.file->f_op != &timerfd_fops) {
	fdput(f);
	return -EINVAL;
	}
	*p = f;
	return 0;
	}

	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;
	}

	static int do_timerfd_settime(int ufd, int flags,
	const struct itimerspec *new,
	struct itimerspec *old)
	{
	struct fd f;
	struct timerfd_ctx *ctx;
	int ret;

	if ((flags & ~TFD_SETTIME_FLAGS) \|\|
	!timespec_valid(&new->it_value) \|\|
	!timespec_valid(&new->it_interval))
	return -EINVAL;

	ret = timerfd_fget(ufd, &f);
	if (ret)
	return ret;
	ctx = f.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);

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

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

	spin_unlock_irq(&ctx->wqh.lock);
	fdput(f);
	return ret;
	}

	static int do_timerfd_gettime(int ufd, struct itimerspec *t)
	{
	struct fd f;
	struct timerfd_ctx *ctx;
	int ret = timerfd_fget(ufd, &f);
	if (ret)
	return ret;
	ctx = f.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);
	}
	t->it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	t->it_interval = ktime_to_timespec(ctx->tintv);
	spin_unlock_irq(&ctx->wqh.lock);
	fdput(f);
	return 0;
	}

	SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
	const struct itimerspec __user *, utmr,
	struct itimerspec __user *, otmr)
	{
	struct itimerspec new, old;
	int ret;

	if (copy_from_user(&new, utmr, sizeof(new)))
	return -EFAULT;
	ret = do_timerfd_settime(ufd, flags, &new, &old);
	if (ret)
	return ret;
	if (otmr && copy_to_user(otmr, &old, sizeof(old)))
	return -EFAULT;

	return ret;
	}

	SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
	{
	struct itimerspec kotmr;
	int ret = do_timerfd_gettime(ufd, &kotmr);
	if (ret)
	return ret;
	return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
	}

	#ifdef CONFIG_COMPAT
	COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
	const struct compat_itimerspec __user *, utmr,
	struct compat_itimerspec __user *, otmr)
	{
	struct itimerspec new, old;
	int ret;

	if (get_compat_itimerspec(&new, utmr))
	return -EFAULT;
	ret = do_timerfd_settime(ufd, flags, &new, &old);
	if (ret)
	return ret;
	if (otmr && put_compat_itimerspec(otmr, &old))
	return -EFAULT;
	return ret;
	}

	COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
	struct compat_itimerspec __user *, otmr)
	{
	struct itimerspec kotmr;
	int ret = do_timerfd_gettime(ufd, &kotmr);
	if (ret)
	return ret;
	return put_compat_itimerspec(otmr, &kotmr) ? -EFAULT: 0;
	}
	#endif