From: Anna-Maria Gleixner <anna-maria@linutronix.de>
Date: Tue, 30 Jul 2019 22:33:51 +0000 (+0200)
Subject: itimers: Prepare for PREEMPT_RT
X-Git-Tag: v5.4-rc1~159^2~62
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c7e6d704a0097e59667495cf52dcc4e1085e620b;p=thirdparty%2Fkernel%2Flinux.git

itimers: Prepare for PREEMPT_RT

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-maria@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190730223828.690771827@linutronix.de
---

diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c
index 02068b2d5862c..9d26fd4ba4c0f 100644
--- a/kernel/time/itimer.c
+++ b/kernel/time/itimer.c
@@ -213,6 +213,7 @@ again:
 		/* 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);