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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 2 Dec 2015 11:34:07 +0100
Subject: [PATCH 127/354] rtmutex: trylock is okay on -RT
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=1d31366fb82713fa3ddb743d9471fb4efdebc49d

non-RT kernel could deadlock on rt_mutex_trylock() in softirq context. On
-RT we don't run softirqs in IRQ context but in thread context so it is
not a issue here.

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 a5ec4f68527e..4bec24dfafc6 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1583,7 +1583,11 @@ int __sched rt_mutex_trylock(struct rt_mutex *lock)
 {
 	int ret;
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+	if (WARN_ON_ONCE(in_irq() || in_nmi()))
+#else
 	if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
+#endif
 		return 0;
 
 	ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);