On 06/15/2016 01:12 PM, Peter Zijlstra wrote:
On Wed, Jun 15, 2016 at 09:56:59AM -0700, Davidlohr Bueso wrote:On Tue, 14 Jun 2016, Waiman Long wrote:+++ 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:I think he'll go rely on it later on. In any case, its fairly simple to cure, just add smp_acquire__after_ctrl_dep() at the end. If we bail because need_resched() we don't need the acquire I think.
Yes, I only need the acquire barrier when the locking is successful. Thanks for the suggestion. I will make the change accordingly.
Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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