The existing version uses a heavy barrier while only release semantics
is required. So use atomic_sub_return_release instead.
Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
---
include/asm-generic/qspinlock.h | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
index 35a52a8..8947cd2 100644
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -92,10 +92,9 @@ static __always_inline void queued_spin_lock(struct qspinlock *lock)
static __always_inline void queued_spin_unlock(struct qspinlock *lock)
{
/*
- * smp_mb__before_atomic() in order to guarantee release semantics
- */
- smp_mb__before_atomic();
- atomic_sub(_Q_LOCKED_VAL, &lock->val);
+ * unlock() need release semantics
+ */
+ (void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val);
}
#endif
--
1.9.1
--
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