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From bcc9f5e2b7eb56660512649787ab651fc138d9e4 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 171/323] locking/rtmutex: Allow rt_mutex_trylock() on
PREEMPT_RT
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
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 35cdbbb5daa9..1bf7a04688c5 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1884,7 +1884,11 @@ 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);
--
2.43.0
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