[PATCH] hrtimers: fix posix-timer requeue race
commitff60a5dc4fa584d47022d2533bc5c53b80096fb5
authorakpm@osdl.org <akpm@osdl.org>
Wed, 1 Feb 2006 11:05:10 +0000 (1 03:05 -0800)
committerLinus Torvalds <torvalds@g5.osdl.org>
Wed, 1 Feb 2006 16:53:13 +0000 (1 08:53 -0800)
tree230e685e1cf26a9ade0e9446d87d41c503444be3
parenta16a1c095a2392d49fafea22f3a508e268ef7167
[PATCH] hrtimers: fix posix-timer requeue race

From: Steven Rostedtrostedt@goodmis.org <rostedt@goodmis.org>

CPU0 expires a posix-timer and runs the callback function.  The signal is
queued.

After releasing the posix-timer lock and before returning to hrtimer_run_queue
CPU0 gets interrupted.  CPU1 delivers the queued signal and rearms the timer.
CPU0 comes back to hrtimer_run_queue and sets the timer state to expired.

The next modification of the timer can result in an oops, because the state
information is wrong.

Keep track of state = RUNNING and check if the state has been in the return
path of hrtimer_run_queue.  In case the state has been changed, ignore a
restart request and do not touch the state variable.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
include/linux/hrtimer.h
kernel/hrtimer.c