[tip:timers/core] hrtimer: Fix hrtimer_is_queued() hole

tip-bot for Peter Zijlstra
2015-06-18T22:19:38Z

Commit-ID: 8edfb0362e8e52dec2de08fa163af01c9da2c9d0
Gitweb: http://git.kernel.org/tip/8edfb0362e8e52dec2de08fa163af01c9da2c9d0
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 11 Jun 2015 14:46:45 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 19 Jun 2015 00:09:56 +0200

hrtimer: Fix hrtimer_is_queued() hole

A queued hrtimer that gets restarted (hrtimer_start*() while
hrtimer_is_queued()) will briefly appear as unqueued/inactive, even
though the timer has always been active, we just moved it.

Close this hole by preserving timer->state in
hrtimer_start_range_ns()'s remove_hrtimer() call.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124743.175989138@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/hrtimer.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index b1b795e..1604157 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -889,10 +889,10 @@ static void __remove_hrtimer(struct hrtimer *timer,
* remove hrtimer, called with base lock held
*/
static inline int
-remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
+remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base, bool restart)
{
if (hrtimer_is_queued(timer)) {
- unsigned long state;
+ unsigned long state = timer->state;
int reprogram;

/*
@@ -906,12 +906,15 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
debug_deactivate(timer);
timer_stats_hrtimer_clear_start_info(timer);
reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
- /*
- * We must preserve the CALLBACK state flag here,
- * otherwise we could move the timer base in
- * switch_hrtimer_base.
- */
- state = timer->state & HRTIMER_STATE_CALLBACK;
+
+ if (!restart) {
+ /*
+ * We must preserve the CALLBACK state flag here,
+ * otherwise we could move the timer base in
+ * switch_hrtimer_base.
+ */
+ state &= HRTIMER_STATE_CALLBACK;
+ }
__remove_hrtimer(timer, base, state, reprogram);
return 1;
}
@@ -936,7 +939,7 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
base = lock_hrtimer_base(timer, &flags);

/* Remove an active timer from the queue: */
- remove_hrtimer(timer, base);
+ remove_hrtimer(timer, base, true);

if (mode & HRTIMER_MODE_REL) {
tim = ktime_add_safe(tim, base->get_time());
@@ -1005,7 +1008,7 @@ int hrtimer_try_to_cancel(struct hrtimer *timer)
base = lock_hrtimer_base(timer, &flags);

if (!hrtimer_callback_running(timer))
- ret = remove_hrtimer(timer, base);
+ ret = remove_hrtimer(timer, base, false);

unlock_hrtimer_base(timer, &flags);