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) <[email protected]> Signed-off-by: Pan Xinhui <[email protected]> --- 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
