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authorakpm@osdl.org <akpm@osdl.org>2006-02-01 03:05:10 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-01 08:53:13 -0800
commitff60a5dc4fa584d47022d2533bc5c53b80096fb5 (patch)
tree230e685e1cf26a9ade0e9446d87d41c503444be3
parenta16a1c095a2392d49fafea22f3a508e268ef7167 (diff)
[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>
-rw-r--r--include/linux/hrtimer.h1
-rw-r--r--kernel/hrtimer.c5
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 089bfb1fa01..c657f3d4924 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -40,6 +40,7 @@ enum hrtimer_restart {
enum hrtimer_state {
HRTIMER_INACTIVE, /* Timer is inactive */
HRTIMER_EXPIRED, /* Timer is expired */
+ HRTIMER_RUNNING, /* Timer is running the callback function */
HRTIMER_PENDING, /* Timer is pending */
};
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f1c4155b49a..f580dd9db28 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -550,6 +550,7 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
fn = timer->function;
data = timer->data;
set_curr_timer(base, timer);
+ timer->state = HRTIMER_RUNNING;
__remove_hrtimer(timer, base);
spin_unlock_irq(&base->lock);
@@ -565,6 +566,10 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
spin_lock_irq(&base->lock);
+ /* Another CPU has added back the timer */
+ if (timer->state != HRTIMER_RUNNING)
+ continue;
+
if (restart == HRTIMER_RESTART)
enqueue_hrtimer(timer, base);
else