Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b215e283992899650c4271e7385c79e26fb9a88e
Commit:     b215e283992899650c4271e7385c79e26fb9a88e
Parent:     6d18c9220965b437287c3a7e803725c24992ceac
Author:     Davide Libenzi <[EMAIL PROTECTED]>
AuthorDate: Thu May 10 22:23:16 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri May 11 08:29:36 2007 -0700

    signal/timer/event: timerfd core
    
    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
    
    [EMAIL PROTECTED]: add sys_timerfd to sys_ni.c]
    Signed-off-by: Davide Libenzi <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 fs/Makefile              |    1 +
 fs/timerfd.c             |  227 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/syscalls.h |    2 +
 include/linux/timerfd.h  |   17 ++++
 init/Kconfig             |   10 ++
 kernel/sys_ni.c          |    1 +
 6 files changed, 258 insertions(+), 0 deletions(-)

diff --git a/fs/Makefile b/fs/Makefile
index cd8a57a..39625da 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_INOTIFY_USER)    += inotify_user.o
 obj-$(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
diff --git a/fs/timerfd.c b/fs/timerfd.c
new file mode 100644
index 0000000..e329e37
--- /dev/null
+++ b/fs/timerfd.c
@@ -0,0 +1,227 @@
+/*
+ *  fs/timerfd.c
+ *
+ *  Copyright (C) 2007  Davide Libenzi <[EMAIL PROTECTED]>
+ *
+ *
+ *  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/list.h>
+#include <linux/spinlock.h>
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/anon_inodes.h>
+#include <linux/timerfd.h>
+
+struct timerfd_ctx {
+       struct hrtimer tmr;
+       ktime_t tintv;
+       spinlock_t lock;
+       wait_queue_head_t wqh;
+       int expired;
+};
+
+/*
+ * 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.
+ */
+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->lock, flags);
+       ctx->expired = 1;
+       wake_up_locked(&ctx->wqh);
+       spin_unlock_irqrestore(&ctx->lock, flags);
+
+       return HRTIMER_NORESTART;
+}
+
+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->expired = 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->expired)
+               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 = 0;
+       DECLARE_WAITQUEUE(wait, current);
+
+       if (count < sizeof(ticks))
+               return -EINVAL;
+       spin_lock_irq(&ctx->lock);
+       res = -EAGAIN;
+       if (!ctx->expired && !(file->f_flags & O_NONBLOCK)) {
+               __add_wait_queue(&ctx->wqh, &wait);
+               for (res = 0;;) {
+                       set_current_state(TASK_INTERRUPTIBLE);
+                       if (ctx->expired) {
+                               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 (ctx->expired) {
+               ctx->expired = 0;
+               if (ctx->tintv.tv64 != 0) {
+                       /*
+                        * 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 = (u32)
+                               hrtimer_forward(&ctx->tmr,
+                                               hrtimer_cb_get_time(&ctx->tmr),
+                                               ctx->tintv);
+                       hrtimer_restart(&ctx->tmr);
+               } else
+                       ticks = 1;
+       }
+       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
+                * 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->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;
+}
+
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e049f14..fc637be 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -605,6 +605,8 @@ asmlinkage long sys_set_robust_list(struct robust_list_head 
__user *head,
                                    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[]);
 
diff --git a/include/linux/timerfd.h b/include/linux/timerfd.h
new file mode 100644
index 0000000..cf2b10d
--- /dev/null
+++ b/include/linux/timerfd.h
@@ -0,0 +1,17 @@
+/*
+ *  include/linux/timerfd.h
+ *
+ *  Copyright (C) 2007  Davide Libenzi <[EMAIL PROTECTED]>
+ *
+ */
+
+#ifndef _LINUX_TIMERFD_H
+#define _LINUX_TIMERFD_H
+
+
+#define TFD_TIMER_ABSTIME (1 << 0)
+
+
+
+#endif /* _LINUX_TIMERFD_H */
+
diff --git a/init/Kconfig b/init/Kconfig
index db70720..02c167d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -502,6 +502,16 @@ config SIGNALFD
 
          If unsure, say Y.
 
+config TIMERFD
+       bool "Enable 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
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 807e9bb..b18f625 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -144,3 +144,4 @@ cond_syscall(sys_ioprio_get);
 
 /* New file descriptors */
 cond_syscall(sys_signalfd);
+cond_syscall(sys_timerfd);
-
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