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authorDavide Libenzi <davidel@xmailserver.org>2007-05-10 22:23:16 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-11 08:29:36 -0700
commitb215e283992899650c4271e7385c79e26fb9a88e (patch)
tree3f950814510422606821f1b0b373d65e4d9ed303 /init
parent6d18c9220965b437287c3a7e803725c24992ceac (diff)
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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/Kconfig10
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