On 2016年05月27日 00:57, Peter Zijlstra wrote:
On Thu, May 26, 2016 at 06:47:29PM +0200, Peter Zijlstra wrote:
On Wed, May 25, 2016 at 04:18:08PM +0800, Pan Xinhui wrote:
cmpxchg_release is light-wight than cmpxchg, we can gain a better
performace then. On some arch like ppc, barrier impact the performace
too much.
Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
---
kernel/locking/qspinlock_paravirt.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index a5b1248..2bbffe4 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -614,7 +614,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock)
* unhash. Otherwise it would be possible to have multiple @lock
* entries, which would be BAD.
*/
- locked = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0);
+ locked = cmpxchg_release(&l->locked, _Q_LOCKED_VAL, 0);
if (likely(locked == _Q_LOCKED_VAL))
return;
This patch fails to explain _why_ it can be relaxed.
And seeing how this cmpxchg() can actually unlock the lock, I don't see
how this can possibly be correct. Maybe cmpxchg_release(), but relaxed
seems very wrong.
Clearly I need to stop working for the day, I cannea read. You're doing
release, not relaxed.
Never mind. thanks for review :)
Still Changelog needs improvement.
Will do that.
thanks
xinhui
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