[tip:locking/core] locking/rtmutex: Only warn once on a trylock from bad context

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  17544d7dc82bc0ce43ba7e3f12d37c6a2337dc01
Gitweb:     http://git.kernel.org/tip/17544d7dc82bc0ce43ba7e3f12d37c6a2337dc01
Author:     Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate: Fri, 27 May 2016 15:47:18 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 3 Jun 2016 12:06:12 +0200

locking/rtmutex: Only warn once on a trylock from bad context

One warning should be enough to get one motivated to fix this. It is
possible that this happens more than once and that starts flooding the
output. Later the prints will be suppressed so we only get half of it.
Depending on the console system used it might not be helpful.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1464356838-1755-1-git-send-email-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/locking/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 3e74660..1ec0f48 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1478,7 +1478,7 @@ EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
  */
 int __sched rt_mutex_trylock(struct rt_mutex *lock)
 {
-	if (WARN_ON(in_irq() || in_nmi() || in_serving_softirq()))
+	if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
 		return 0;
 
 	return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);