From 60eb8f49978507bd52fc08c758732fbab97163ef Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 2 Dec 2015 11:34:07 +0100
Subject: [PATCH 171/327] locking/rtmutex: Allow rt_mutex_trylock() on
 PREEMPT_RT

Non PREEMPT_RT kernel can deadlock on rt_mutex_trylock() in softirq
context.
On PREEMPT_RT the softirq context is handled in thread context. This
avoids the deadlock in the slow path and PI-boosting will be done on the
correct thread.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/locking/rtmutex.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index d06f3760473b..99cb78e1a3da 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1887,7 +1887,11 @@ int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
 
 int __sched __rt_mutex_trylock(struct rt_mutex *lock)
 {
+#ifdef CONFIG_PREEMPT_RT
+	if (WARN_ON_ONCE(in_irq() || in_nmi()))
+#else
 	if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
+#endif
 		return 0;
 
 	return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);
-- 
2.49.0

