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| author | Davide Libenzi <davidel@xmailserver.org> | 2007-05-10 22:23:16 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-11 08:29:36 -0700 |
| commit | b215e283992899650c4271e7385c79e26fb9a88e (patch) | |
| tree | 3f950814510422606821f1b0b373d65e4d9ed303 /init | |
| parent | 6d18c9220965b437287c3a7e803725c24992ceac (diff) | |
| download | linux-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 'init')
| -rw-r--r-- | init/Kconfig | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig index db707204b751..02c167de9646 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 |