From: Sebastian Andrzej Siewior Date: Wed 02 Dec 2015 11:34:07 +0100 Subject: rtmutex: trylock is okay on -RT Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.17-rt8.tar.xz 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 --- kernel/locking/rtmutex.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1962,7 +1962,11 @@ EXPORT_SYMBOL_GPL(rt_mutex_timed_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);