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Date: Sun, 3 Aug 2014 22:36:16 -0400 From: Waiman Long <Waiman.Long@...com> To: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org> Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org, linux-doc@...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 1/7] locking/rwsem: don't resched at the end of optimistic spinning For a fully preemptive kernel, a call to preempt_enable() could potentially trigger a task rescheduling event. In the case of rwsem optimistic spinning, the task has either gotten the lock or is going to sleep soon. So there is no point to do rescheduling here. Signed-off-by: Waiman Long <Waiman.Long@...com> --- kernel/locking/rwsem-xadd.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a2391ac..d058946 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -385,7 +385,11 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem) } osq_unlock(&sem->osq); done: - preempt_enable(); + /* + * Don't need to do rescheduling here as we either got the lock or + * is going to sleep soon. + */ + preempt_enable_no_resched(); return taken; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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