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* [PATCH tip/locking/core 1/3] locking/qspinlock: Use smp_cond_acquire() in pending code
@ 2015-12-10 20:17 Waiman Long
  2015-12-10 20:17 ` [PATCH tip/locking/core 2/3] locking/pvqspinlock: Enable slowpath locking count tracking Waiman Long
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Waiman Long @ 2015-12-10 20:17 UTC (permalink / raw)
  To: Peter Zijlstra, Ingo Molnar
  Cc: linux-kernel, Scott J Norton, Douglas Hatch, Waiman Long

The newly introduced smp_cond_acquire() was used to replace the
slowpath lock acquisition loop. Similarly, the new function can also
be applied to the pending bit locking loop. This patch uses the new
function in that loop.

Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
---
 kernel/locking/qspinlock.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 393d187..ce2f75e 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -358,8 +358,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 	 * sequentiality; this is because not all clear_pending_set_locked()
 	 * implementations imply full barriers.
 	 */
-	while ((val = smp_load_acquire(&lock->val.counter)) & _Q_LOCKED_MASK)
-		cpu_relax();
+	smp_cond_acquire(!(atomic_read(&lock->val) & _Q_LOCKED_MASK));
 
 	/*
 	 * take ownership and clear the pending bit.
@@ -435,7 +434,7 @@ queue:
 	 *
 	 * The PV pv_wait_head_or_lock function, if active, will acquire
 	 * the lock and return a non-zero value. So we have to skip the
-	 * smp_load_acquire() call. As the next PV queue head hasn't been
+	 * smp_cond_acquire() call. As the next PV queue head hasn't been
 	 * designated yet, there is no way for the locked value to become
 	 * _Q_SLOW_VAL. So both the set_locked() and the
 	 * atomic_cmpxchg_relaxed() calls will be safe.
@@ -466,7 +465,7 @@ locked:
 			break;
 		}
 		/*
-		 * The smp_load_acquire() call above has provided the necessary
+		 * The smp_cond_acquire() call above has provided the necessary
 		 * acquire semantics required for locking. At most two
 		 * iterations of this loop may be ran.
 		 */
-- 
1.7.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-02-29 11:22 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2015-12-10 20:17 [PATCH tip/locking/core 1/3] locking/qspinlock: Use smp_cond_acquire() in pending code Waiman Long
2015-12-10 20:17 ` [PATCH tip/locking/core 2/3] locking/pvqspinlock: Enable slowpath locking count tracking Waiman Long
2016-02-29 11:21   ` [tip:locking/core] " tip-bot for Waiman Long
2015-12-10 20:17 ` [PATCH tip/locking/core 3/3] locking/pvqspinlock: Direct lock stealing count tracking in pv_queued_spin_steal_lock Waiman Long
2016-02-29 11:20   ` [tip:locking/core] locking/pvqspinlock: Move lock stealing count tracking code into pv_queued_spin_steal_lock() tip-bot for Waiman Long
2016-02-29 11:20 ` [tip:locking/core] locking/qspinlock: Use smp_cond_acquire() in pending code tip-bot for Waiman Long

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