[patch 3/7] itimers: Prepare for PREEMPT_RT

[Thomas Gleixner]

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

As a benefit the retry loop gains the missing cpu_relax() on !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/itimer.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/time/itimer.c
+++ b/kernel/time/itimer.c
@@ -213,6 +213,7 @@ int do_setitimer(int which, struct itime
                /* We are sharing ->siglock with it_real_fn() */
                if (hrtimer_try_to_cancel(timer) < 0) {
                        spin_unlock_irq(&tsk->sighand->siglock);
+                       hrtimer_cancel_wait_running(timer);
                        goto again;
                }
                expires = timeval_to_ktime(value->it_value);