Re: [PATCH] locking/rwsem: reduce spinlock contention in wakeup after up_read/up_write

From: Waiman Long
Date: Wed Apr 22 2015 - 16:19:35 EST


On 04/20/2015 04:23 PM, Jason Low wrote:
On Fri, 2015-04-17 at 22:03 -0400, Waiman Long wrote:

diff --git a/include/linux/osq_lock.h b/include/linux/osq_lock.h
index 3a6490e..703ea5c 100644
--- a/include/linux/osq_lock.h
+++ b/include/linux/osq_lock.h
@@ -32,4 +32,9 @@ static inline void osq_lock_init(struct optimistic_spin_queue *lock)
extern bool osq_lock(struct optimistic_spin_queue *lock);
extern void osq_unlock(struct optimistic_spin_queue *lock);

+static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
+{
+ return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
+}
Would it be better to separate the addition of osq_is_locked() into its
own patch, since this can be useful for other situations and isn't just
specific to the rwsem optimization.


I think the osq_lock.h change is too simple and straight forward to warrant a separate patch.

Cheers,
Longman
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