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Date:	Thu,  7 Aug 2014 18:26:44 -0400
From:	Waiman Long <Waiman.Long@...com>
To:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Davidlohr Bueso <davidlohr@...com>,
	Jason Low <jason.low2@...com>,
	Scott J Norton <scott.norton@...com>,
	Waiman Long <Waiman.Long@...com>
Subject: [PATCH v2 3/7] locking/rwsem: rwsem_can_spin_on_owner can be called with preemption enabled

The rwsem_can_spin_on_owner() function can be called with preemption
enabled. This patch moves it before preempt_disable() so that it won't
do unnecessary preemption operations when spinning is not possible.

Signed-off-by: Waiman Long <Waiman.Long@...com>
---
 kernel/locking/rwsem-xadd.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index ddd56d2..c8887ba 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -404,11 +404,11 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
 	bool taken = false;
 	int  spincnt = 0;
 
-	preempt_disable();
-
 	/* sem->wait_lock should not be held when doing optimistic spinning */
 	if (!rwsem_can_spin_on_owner(sem))
-		goto done;
+		return false;
+
+	preempt_disable();
 
 	if (!osq_lock(&sem->osq))
 		goto done;
-- 
1.7.1

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