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author | Davide Libenzi <davidel@xmailserver.org> | 2007-05-10 22:23:16 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-11 08:29:36 -0700 |
commit | b215e283992899650c4271e7385c79e26fb9a88e (patch) | |
tree | 3f950814510422606821f1b0b373d65e4d9ed303 /include/linux/timerfd.h | |
parent | 6d18c9220965b437287c3a7e803725c24992ceac (diff) | |
download | kernel_samsung_espresso10-b215e283992899650c4271e7385c79e26fb9a88e.zip kernel_samsung_espresso10-b215e283992899650c4271e7385c79e26fb9a88e.tar.gz kernel_samsung_espresso10-b215e283992899650c4271e7385c79e26fb9a88e.tar.bz2 |
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
[akpm@linux-foundation.org: add sys_timerfd to sys_ni.c]
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/timerfd.h')
-rw-r--r-- | include/linux/timerfd.h | 17 |
1 files changed, 17 insertions, 0 deletions
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 <davidel@xmailserver.org> + * + */ + +#ifndef _LINUX_TIMERFD_H +#define _LINUX_TIMERFD_H + + +#define TFD_TIMER_ABSTIME (1 << 0) + + + +#endif /* _LINUX_TIMERFD_H */ + |