From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 27 Mar 2018 15:58:16 +0200
Subject: alarmtimer: Prevent live lock in alarm_cancel()
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 51e376c469bf05f32cb1ceb9e39d31bb92f1f6c8
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension
If alarm_try_to_cancel() requires a retry, then depending on the
priority setting the retry loop might prevent timer callback completion
on RT. Prevent that by waiting for completion on RT, no change for a
non RT kernel.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
kernel/time/alarmtimer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -442,7 +442,7 @@ int alarm_cancel(struct alarm *alarm)
int ret = alarm_try_to_cancel(alarm);
if (ret >= 0)
return ret;
- cpu_relax();
+ hrtimer_wait_for_timer(&alarm->timer);
}
}
EXPORT_SYMBOL_GPL(alarm_cancel);