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rtmutex: Warn if trylock is called from hard/softirq context

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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 <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
This commit is contained in:
Thomas Gleixner 2015-05-13 22:49:12 +02:00
parent a22e5f579b
commit 6ce47fd961
1 changed files with 7 additions and 0 deletions
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7
kernel/locking/rtmutex.c
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@ -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);