On Tue, 14 Jun 2016, Waiman Long wrote:
The osq_lock() and osq_unlock() function may not provide the necessary
acquire and release barrier in some cases. This patch makes sure
that the proper barriers are provided when osq_lock() is successful
or when osq_unlock() is called.
Signed-off-by: Waiman Long <Waiman.Long@xxxxxxx>
---
kernel/locking/osq_lock.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 05a3785..7dd4ee5 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -115,7 +115,7 @@ bool osq_lock(struct optimistic_spin_queue *lock)
* cmpxchg in an attempt to undo our queueing.
*/
- while (!READ_ONCE(node->locked)) {
+ while (!smp_load_acquire(&node->locked)) {
Hmm this being a polling path, that barrier can get pretty expensive and
last I checked it was unnecessary:
036cc30c6b6 (locking/osq: No need for load/acquire when acquire-polling)
Thanks,
Davidlohr
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