Re: [patch 2/4] new timerfd API v2 - new timerfd API
From: roel
Date: Mon Sep 24 2007 - 18:50:49 EST
Davide Libenzi wrote:
> This is the new timerfd API as it is implemented by the following patch:
>
> int timerfd_create(int clockid);
> int timerfd_settime(int ufd, int flags,
> const struct itimerspec *utmr,
> struct itimerspec *otmr);
> int timerfd_gettime(int ufd, struct itimerspec *otmr);
>
> The timerfd_create() API creates an un-programmed timerfd fd. The "clockid"
> parameter can be either CLOCK_MONOTONIC or CLOCK_REALTIME.
> The timerfd_settime() API give new settings by the timerfd fd, by optionally
> retrieving the previous expiration time (in case the "otmr" parameter is not NULL).
> The time value specified in "utmr" is absolute, if the TFD_TIMER_ABSTIME bit
> is set in the "flags" parameter. Otherwise it's a relative time.
> The timerfd_gettime() API returns the next expiration time of the timer, or {0, 0}
> if the timerfd has not been set yet.
> Like the previous timerfd API implementation, read(2) and poll(2) are supported
> (with the same interface).
> Here's a simple test program I used to exercise the new timerfd APIs:
>
> http://www.xmailserver.org/timerfd-test2.c
>
>
>
> Signed-off-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
>
>
> - Davide
>
>
> ---
> fs/compat.c | 32 ++++++-
> fs/timerfd.c | 197 ++++++++++++++++++++++++++++++-----------------
> include/linux/compat.h | 7 +
> include/linux/syscalls.h | 7 +
> 4 files changed, 164 insertions(+), 79 deletions(-)
>
> Index: linux-2.6.mod/fs/timerfd.c
> ===================================================================
> --- linux-2.6.mod.orig/fs/timerfd.c 2007-09-24 12:26:19.000000000 -0700
> +++ linux-2.6.mod/fs/timerfd.c 2007-09-24 12:31:22.000000000 -0700
> @@ -25,13 +25,15 @@
> struct hrtimer tmr;
> ktime_t tintv;
> wait_queue_head_t wqh;
> + u64 ticks;
> int expired;
> + int clockid;
> };
>
> /*
> * 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 read.
> + * tintv.tv64 != 0) until the timer is accessed.
> */
> static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
> {
> @@ -40,13 +42,14 @@
>
> 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;
> }
>
> -static void timerfd_setup(struct timerfd_ctx *ctx, int clockid, int flags,
> +static void timerfd_setup(struct timerfd_ctx *ctx, int flags,
> const struct itimerspec *ktmr)
> {
> enum hrtimer_mode htmode;
> @@ -57,8 +60,9 @@
>
> 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_init(&ctx->tmr, ctx->clockid, htmode);
> ctx->tmr.expires = texp;
> ctx->tmr.function = timerfd_tmrproc;
> if (texp.tv64 != 0)
> @@ -83,7 +87,7 @@
> poll_wait(file, &ctx->wqh, wait);
>
> spin_lock_irqsave(&ctx->wqh.lock, flags);
> - if (ctx->expired)
> + if (ctx->ticks)
> events |= POLLIN;
> spin_unlock_irqrestore(&ctx->wqh.lock, flags);
>
> @@ -102,11 +106,11 @@
> return -EINVAL;
> spin_lock_irq(&ctx->wqh.lock);
> res = -EAGAIN;
> - if (!ctx->expired && !(file->f_flags & O_NONBLOCK)) {
> + if (!ctx->ticks && !(file->f_flags & O_NONBLOCK)) {
> __add_wait_queue(&ctx->wqh, &wait);
> for (res = 0;;) {
> set_current_state(TASK_INTERRUPTIBLE);
> - if (ctx->expired) {
> + if (ctx->ticks) {
> res = 0;
> break;
> }
> @@ -121,22 +125,21 @@
> __remove_wait_queue(&ctx->wqh, &wait);
> __set_current_state(TASK_RUNNING);
> }
> - if (ctx->expired) {
> - ctx->expired = 0;
> - if (ctx->tintv.tv64 != 0) {
> + 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 = (u64)
> - hrtimer_forward(&ctx->tmr,
> - hrtimer_cb_get_time(&ctx->tmr),
> - ctx->tintv);
> + ticks += (u64) hrtimer_forward_now(&ctx->tmr,
> + ctx->tintv) - 1;
> hrtimer_restart(&ctx->tmr);
> - } else
> - ticks = 1;
> + }
> + ctx->expired = 0;
> + ctx->ticks = 0;
> }
> spin_unlock_irq(&ctx->wqh.lock);
> if (ticks)
> @@ -150,76 +153,130 @@
> .read = timerfd_read,
> };
>
> -asmlinkage long sys_timerfd(int ufd, int clockid, int flags,
> - const struct itimerspec __user *utmr)
> +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;
> +}
> +
> +asmlinkage long sys_timerfd_create(int clockid)
> {
> - int error;
> + int error, ufd;
> struct timerfd_ctx *ctx;
> struct file *file;
> struct inode *inode;
> - struct itimerspec ktmr;
> -
> - if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
> - return -EFAULT;
>
> if (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);
> +
> + error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]",
> + &timerfd_fops, ctx);
> + if (error) {
> + kfree(ctx);
> + return error;
> + }
> +
> + return ufd;
> +}
> +
> +asmlinkage long sys_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;
> +
> + if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
> + return -EFAULT;
> +
> if (!timespec_valid(&ktmr.it_value) ||
> !timespec_valid(&ktmr.it_interval))
> return -EINVAL;
>
> - if (ufd == -1) {
> - ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
> - if (!ctx)
> - return -ENOMEM;
> -
> - init_waitqueue_head(&ctx->wqh);
> -
> - timerfd_setup(ctx, clockid, flags, &ktmr);
> -
> - /*
> - * When we call this, the initialization must be complete, since
> - * anon_inode_getfd() will install the fd.
> - */
> - error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]",
> - &timerfd_fops, ctx);
> - if (error)
> - goto err_tmrcancel;
> - } else {
> - file = fget(ufd);
> - if (!file)
> - return -EBADF;
> - ctx = file->private_data;
> - if (file->f_op != &timerfd_fops) {
> - fput(file);
> - return -EINVAL;
> - }
> - /*
> - * 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();
> - }
> - /*
> - * Re-program the timer to the new value ...
> - */
> - timerfd_setup(ctx, clockid, flags, &ktmr);
> -
> + file = timerfd_fget(ufd);
> + if (IS_ERR(file))
> + return PTR_ERR(file);
> + ctx = file->private_data;
> +
> + /*
> + * 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);
> - fput(file);
> + cpu_relax();
> }
>
> - return ufd;
> + /*
> + * 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(ctx->tmr.expires);
> + kotmr.it_interval = ktime_to_timespec(ctx->tintv);
> +
> + /*
> + * Re-program the timer to the new value ...
> + */
> + timerfd_setup(ctx, flags, &ktmr);
>
> -err_tmrcancel:
> - hrtimer_cancel(&ctx->tmr);
> - kfree(ctx);
> - return error;
> + spin_unlock_irq(&ctx->wqh.lock);
> + fput(file);
> + if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +asmlinkage long sys_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 += (u64)
> + hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
> + hrtimer_restart(&ctx->tmr);
> + }
> + kotmr.it_value = ktime_to_timespec(ctx->tmr.expires);
> + 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;
> }
>
> Index: linux-2.6.mod/include/linux/syscalls.h
> ===================================================================
> --- linux-2.6.mod.orig/include/linux/syscalls.h 2007-09-24 12:26:19.000000000 -0700
> +++ linux-2.6.mod/include/linux/syscalls.h 2007-09-24 12:30:17.000000000 -0700
> @@ -607,8 +607,11 @@
> size_t len);
> asmlinkage long sys_getcpu(unsigned __user *cpu, unsigned __user *node, struct getcpu_cache __user *cache);
> asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask);
> -asmlinkage long sys_timerfd(int ufd, int clockid, int flags,
> - const struct itimerspec __user *utmr);
> +asmlinkage long sys_timerfd_create(int clockid);
> +asmlinkage long sys_timerfd_settime(int ufd, int flags,
> + const struct itimerspec __user *utmr,
> + struct itimerspec __user *otmr);
> +asmlinkage long sys_timerfd_gettime(int ufd, struct itimerspec __user *otmr);
> asmlinkage long sys_eventfd(unsigned int count);
> asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len);
>
> Index: linux-2.6.mod/fs/compat.c
> ===================================================================
> --- linux-2.6.mod.orig/fs/compat.c 2007-09-24 12:26:19.000000000 -0700
> +++ linux-2.6.mod/fs/compat.c 2007-09-24 12:30:17.000000000 -0700
> @@ -2210,19 +2210,41 @@
>
> #ifdef CONFIG_TIMERFD
>
> -asmlinkage long compat_sys_timerfd(int ufd, int clockid, int flags,
> - const struct compat_itimerspec __user *utmr)
> +asmlinkage long compat_sys_timerfd_settime(int ufd, int flags,
> + const struct compat_itimerspec __user *utmr,
> + struct compat_itimerspec __user *otmr)
> {
> + int error;
> struct itimerspec t;
> struct itimerspec __user *ut;
>
> if (get_compat_itimerspec(&t, utmr))
> return -EFAULT;
> - ut = compat_alloc_user_space(sizeof(*ut));
> - if (copy_to_user(ut, &t, sizeof(t)))
> + ut = compat_alloc_user_space(2 * sizeof(struct itimerspec));
> + if (copy_to_user(&ut[0], &t, sizeof(t)))
> return -EFAULT;
> + error = sys_timerfd_settime(ufd, flags, &ut[0], &ut[1]);
> + if (!error && otmr)
> + error = (copy_from_user(&t, &ut[1], sizeof(struct itimerspec)) ||
> + put_compat_itimerspec(otmr, &t)) ? -EFAULT: 0;
I guess this should work as well (and looks clearer):
if (!error && otmr)
if ( copy_from_user(&t, &ut[1], sizeof(struct itimerspec)) ||
put_compat_itimerspec(otmr, &t))
error = -EFAULT;
>
> - return sys_timerfd(ufd, clockid, flags, ut);
> + return error;
> +}
> +
> +asmlinkage long compat_sys_timerfd_gettime(int ufd,
> + struct compat_itimerspec __user *otmr)
> +{
> + int error;
> + struct itimerspec t;
> + struct itimerspec __user *ut;
> +
> + ut = compat_alloc_user_space(sizeof(struct itimerspec));
> + error = sys_timerfd_gettime(ufd, ut);
> + if (!error)
> + error = (copy_from_user(&t, ut, sizeof(struct itimerspec)) ||
> + put_compat_itimerspec(otmr, &t)) ? -EFAULT: 0;
or:
if (!error)
if ( copy_from_user(&t, &ut, sizeof(struct itimerspec)) ||
put_compat_itimerspec(otmr, &t))
error = -EFAULT;
> +
> + return error;
> }
>
> #endif /* CONFIG_TIMERFD */
> Index: linux-2.6.mod/include/linux/compat.h
> ===================================================================
> --- linux-2.6.mod.orig/include/linux/compat.h 2007-09-24 12:26:19.000000000 -0700
> +++ linux-2.6.mod/include/linux/compat.h 2007-09-24 12:30:17.000000000 -0700
> @@ -264,8 +264,11 @@
> asmlinkage long compat_sys_signalfd(int ufd,
> const compat_sigset_t __user *sigmask,
> compat_size_t sigsetsize);
> -asmlinkage long compat_sys_timerfd(int ufd, int clockid, int flags,
> - const struct compat_itimerspec __user *utmr);
> +asmlinkage long compat_sys_timerfd_settime(int ufd, int flags,
> + const struct compat_itimerspec __user *utmr,
> + struct compat_itimerspec __user *otmr);
> +asmlinkage long compat_sys_timerfd_gettime(int ufd,
> + struct compat_itimerspec __user *otmr);
>
> #endif /* CONFIG_COMPAT */
> #endif /* _LINUX_COMPAT_H */
>
> -
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