From 6ce47fd961fa8fb206433789d7754c73cab3b5d0 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 13 May 2015 22:49:12 +0200 Subject: [PATCH] rtmutex: Warn if trylock is called from hard/softirq context rt_mutex_trylock() must be called from thread context. It can be called from atomic regions (preemption or interrupts disabled), but not from hard/softirq/nmi context. Add a warning to alert abusers. The reasons for this are: 1) There is a potential deadlock in the slowpath 2) Another cpu which blocks on the rtmutex will boost the task which allegedly locked the rtmutex, but that cannot work because the hard/softirq context borrows the task context. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Sebastian Siewior --- kernel/locking/rtmutex.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 27dff663f9e4..5fa042be94d5 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1441,10 +1441,17 @@ EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); * * @lock: the rt_mutex to be locked * + * This function can only be called in thread context. It's safe to + * call it from atomic regions, but not from hard interrupt or soft + * interrupt context. + * * Returns 1 on success and 0 on contention */ int __sched rt_mutex_trylock(struct rt_mutex *lock) { + if (WARN_ON(in_irq() || in_nmi() || in_serving_softirq())) + return 0; + return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); } EXPORT_SYMBOL_GPL(rt_mutex_trylock);