This patch introduces a new system call for timers events delivered though file descriptors. This allows timer event to be used with standard POSIX poll(2), select(2) and read(2). As a consequence of supporting the Linux f_op->poll subsystem, they can be used with epoll(2) too. The system call is defined as:
int timerfd(int ufd, int clockid, int flags, const struct itimerspec *utmr); The "ufd" parameter allows for re-use (re-programming) of an existing timerfd w/out going through the close/open cycle (same as signalfd). If "ufd" is -1, s new file descriptor will be created, otherwise the existing "ufd" will be re-programmed. The "clockid" parameter is either CLOCK_MONOTONIC or CLOCK_REALTIME. The time specified in the "utmr->it_value" parameter is the expiry time for the timer. If the TFD_TIMER_ABSTIME flag is set in "flags", this is an absolute time, otherwise it's a relative time. If the time specified in the "utmr->it_interval" is not zero (.tv_sec == 0, tv_nsec == 0), this is the period at which the following ticks should be generated. The "utmr->it_interval" should be set to zero if only one tick is requested. Setting the "utmr->it_value" to zero will disable the timer, or will create a timerfd without the timer enabled. The function returns the new (or same, in case "ufd" is a valid timerfd descriptor) file, or -1 in case of error. As stated before, the timerfd file descriptor supports poll(2), select(2) and epoll(2). When a timer event happened on the timerfd, a POLLIN mask will be returned. The read(2) call can be used, and it will return a u32 variable holding the number of "ticks" that happened on the interface since the last call to read(2). The read(2) call supportes the O_NONBLOCK flag too, and EAGAIN will be returned if no ticks happened. A quick test program, shows timerfd working correctly on my amd64 box: http://www.xmailserver.org/timerfd-test.c Signed-off-by: Davide Libenzi <davidel@xmailserver.org> - Davide Index: linux-2.6.21-rc5.fds/fs/timerfd.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6.21-rc5.fds/fs/timerfd.c 2007-03-31 12:46:14.000000000 -0700 @@ -0,0 +1,233 @@ +/* + * 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/slab.h> +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/signal.h> +#include <linux/list.h> +#include <linux/spinlock.h> +#include <linux/time.h> +#include <linux/hrtimer.h> +#include <linux/jiffies.h> +#include <linux/anon_inodes.h> +#include <linux/timerfd.h> + +#include <asm/uaccess.h> + + +struct timerfd_ctx { + struct hrtimer tmr; + ktime_t tintv; + spinlock_t lock; + wait_queue_head_t wqh; + /* + * Every time a timer triggers, we increase "ticks". A read(2) + * will return the current value, and will reset "ticks" to zero. + */ + u32 ticks; +}; + + +/* + * This gets called when the timer event triggers. We increment the + * tick count and wake the possible waiters. If the timer in a + * sequential one (->tintv.tv64 != 0), we re-arm it with hrtimer_forward(). + */ +static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) +{ + struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); + enum hrtimer_restart rval = HRTIMER_NORESTART; + unsigned long flags; + + spin_lock_irqsave(&ctx->lock, flags); + ctx->ticks++; + wake_up_locked(&ctx->wqh); + if (ctx->tintv.tv64 != 0) { + hrtimer_forward(htmr, hrtimer_cb_get_time(htmr), ctx->tintv); + rval = HRTIMER_RESTART; + } + spin_unlock_irqrestore(&ctx->lock, flags); + + return rval; +} + +static void timerfd_setup(struct timerfd_ctx *ctx, int clockid, int flags, + const struct itimerspec *ktmr) +{ + enum hrtimer_mode htmode; + ktime_t texp; + + htmode = (flags & TFD_TIMER_ABSTIME) ? + HRTIMER_MODE_ABS: HRTIMER_MODE_REL; + + texp = timespec_to_ktime(ktmr->it_value); + ctx->ticks = 0; + ctx->tintv = timespec_to_ktime(ktmr->it_interval); + hrtimer_init(&ctx->tmr, clockid, htmode); + ctx->tmr.expires = texp; + ctx->tmr.function = timerfd_tmrproc; + if (texp.tv64 != 0) + hrtimer_start(&ctx->tmr, texp, htmode); +} + +static int timerfd_release(struct inode *inode, struct file *file) +{ + struct timerfd_ctx *ctx = file->private_data; + + hrtimer_cancel(&ctx->tmr); + kfree(ctx); + 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->lock, flags); + if (ctx->ticks) + events |= POLLIN; + spin_unlock_irqrestore(&ctx->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; + u32 ticks; + DECLARE_WAITQUEUE(wait, current); + + if (count < sizeof(ticks)) + return -EINVAL; + spin_lock_irq(&ctx->lock); + res = -EAGAIN; + ticks = ctx->ticks; + if (ticks == 0 && !(file->f_flags & O_NONBLOCK)) { + __add_wait_queue(&ctx->wqh, &wait); + for (res = 0;;) { + set_current_state(TASK_INTERRUPTIBLE); + ticks = ctx->ticks; + if (ticks != 0) { + res = 0; + break; + } + if (signal_pending(current)) { + res = -ERESTARTSYS; + break; + } + spin_unlock_irq(&ctx->lock); + schedule(); + spin_lock_irq(&ctx->lock); + } + __remove_wait_queue(&ctx->wqh, &wait); + __set_current_state(TASK_RUNNING); + } + if (ticks) + ctx->ticks = 0; + spin_unlock_irq(&ctx->lock); + if (ticks) + res = put_user(ticks, buf) ? -EFAULT: sizeof(ticks); + return res; +} + + +static const struct file_operations timerfd_fops = { + .release = timerfd_release, + .poll = timerfd_poll, + .read = timerfd_read, +}; + + +asmlinkage long sys_timerfd(int ufd, int clockid, int flags, + const struct itimerspec __user *utmr) +{ + int error; + 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; + 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); + spin_lock_init(&ctx->lock); + + timerfd_setup(ctx, clockid, flags, &ktmr); + + /* + * When we call this, the initialization must be complete, since + * aino_getfd() will install the fd. + */ + error = aino_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->lock); + if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) + break; + spin_unlock_irq(&ctx->lock); + cpu_relax(); + } + /* + * Re-program the timer to the new value ... + */ + timerfd_setup(ctx, clockid, flags, &ktmr); + + spin_unlock_irq(&ctx->lock); + fput(file); + } + + return ufd; + +err_tmrcancel: + hrtimer_cancel(&ctx->tmr); + kfree(ctx); + return error; +} + Index: linux-2.6.21-rc5.fds/include/linux/timerfd.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6.21-rc5.fds/include/linux/timerfd.h 2007-03-31 12:30:36.000000000 -0700 @@ -0,0 +1,17 @@ +/* + * include/linux/timerfd.h + * + * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> + * + */ + +#ifndef _LINUX_TIMERFD_H +#define _LINUX_TIMERFD_H + + +#define TFD_TIMER_ABSTIME (1 << 0) + + + +#endif /* _LINUX_TIMERFD_H */ + Index: linux-2.6.21-rc5.fds/include/linux/syscalls.h =================================================================== --- linux-2.6.21-rc5.fds.orig/include/linux/syscalls.h 2007-03-31 12:29:28.000000000 -0700 +++ linux-2.6.21-rc5.fds/include/linux/syscalls.h 2007-03-31 12:45:37.000000000 -0700 @@ -603,6 +603,8 @@ 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); int kernel_execve(const char *filename, char *const argv[], char *const envp[]); Index: linux-2.6.21-rc5.fds/fs/Makefile =================================================================== --- linux-2.6.21-rc5.fds.orig/fs/Makefile 2007-03-31 12:29:28.000000000 -0700 +++ linux-2.6.21-rc5.fds/fs/Makefile 2007-03-31 12:45:37.000000000 -0700 @@ -24,6 +24,7 @@ obj-$(CONFIG_EPOLL) += eventpoll.o obj-$(CONFIG_ANON_INODES) += anon_inodes.o obj-$(CONFIG_SIGNALFD) += signalfd.o +obj-$(CONFIG_TIMERFD) += timerfd.o obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o nfsd-$(CONFIG_NFSD) := nfsctl.o Index: linux-2.6.21-rc5.fds/init/Kconfig =================================================================== --- linux-2.6.21-rc5.fds.orig/init/Kconfig 2007-03-31 12:29:28.000000000 -0700 +++ linux-2.6.21-rc5.fds/init/Kconfig 2007-03-31 12:45:38.000000000 -0700 @@ -483,6 +483,16 @@ If unsure, say Y. +config TIMERFD + bool "Eanble timerfd() system call" if EMBEDDED + depends on ANON_INODES + default y + help + Enable the timerfd() system call that allows to receive timer + events on a file descriptor. + + If unsure, say Y. + config SHMEM bool "Use full shmem filesystem" if EMBEDDED default y - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
