Commit-ID: 6ce47fd961fa8fb206433789d7754c73cab3b5d0
Gitweb: http://git.kernel.org/tip/6ce47fd961fa8fb206433789d7754c73cab3b5d0
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 13 May 2015 22:49:12 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 13 May 2015 22:49:12 +0200
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 <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sebastian Siewior <bigeasy@xxxxxxxxxxxxx>
---
kernel/locking/rtmutex.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 27dff66..5fa042b 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);
--
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