[patch 1/7] alarmtimer: Prepare for PREEMPT_RT

[Thomas Gleixner]

Use the hrtimer_cancel_wait_running() synchronization mechanism to prevent
priority inversion and live locks on PREEMPT_RT.

[ tglx: Split out of combo patch ]

Signed-off-by: Anna-Maria Gleixner <anna-ma...@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 kernel/time/alarmtimer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -432,7 +432,7 @@ int alarm_cancel(struct alarm *alarm)
                int ret = alarm_try_to_cancel(alarm);
                if (ret >= 0)
                        return ret;
-               cpu_relax();
+               hrtimer_cancel_wait_running(&alarm->timer);
        }
 }
 EXPORT_SYMBOL_GPL(alarm_cancel);