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From 50f8ea4c311b4bc5100595c2c43f02754afa2798 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 076/191] 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 03ffb955b286..f0bc7fcae441 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1866,7 +1866,11 @@ 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);
-- 
2.19.1