[tip:sched/core] sched/deadline, locking/rtmutex: Fix open coded check in rt_mutex_waiter_less()

[tip-bot for Juri Lelli <tipbot@zytor.com>]

Commit-ID:  f52405757e4e9bddd868d6b8ca501d58f292969f
Gitweb:     http://git.kernel.org/tip/f52405757e4e9bddd868d6b8ca501d58f292969f
Author:     Juri Lelli <juri.lelli@arm.com>
AuthorDate: Wed, 2 Sep 2015 11:01:35 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 23 Sep 2015 09:51:25 +0200

sched/deadline, locking/rtmutex: Fix open coded check in rt_mutex_waiter_less()

rt_mutex_waiter_less() check of task deadlines is open coded. Since this
is subject to wraparound bugs, make it use the correct helper.

Reported-by: Luca Abeni <luca.abeni@unitn.it>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1441188096-23021-4-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/locking/rtmutex.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 7781d80..35e9bfc 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -158,7 +158,8 @@ rt_mutex_waiter_less(struct rt_mutex_waiter *left,
 	 * then right waiter has a dl_prio() too.
 	 */
 	if (dl_prio(left->prio))
-		return (left->task->dl.deadline < right->task->dl.deadline);
+		return dl_time_before(left->task->dl.deadline,
+				      right->task->dl.deadline);
 
 	return 0;
 }