diff options
| author | Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> | 2016-06-03 16:38:14 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-06-08 15:17:01 +0200 |
| commit | ca50e426f96c905e7d14a9c7a6bd4e0330516047 (patch) | |
| tree | e21ab5d1ec87777e8ebdf3d599de233648bc570b | |
| parent | 6428671bae97caa7040e24e79e969fd87908f4f3 (diff) | |
| download | lwn-ca50e426f96c905e7d14a9c7a6bd4e0330516047.tar.gz lwn-ca50e426f96c905e7d14a9c7a6bd4e0330516047.zip | |
locking/qspinlock: Use atomic_sub_return_release() in queued_spin_unlock()
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@infradead.org>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arnd@arndb.de
Cc: waiman.long@hp.com
Link: http://lkml.kernel.org/r/1464943094-3129-1-git-send-email-xinhui.pan@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | include/asm-generic/qspinlock.h | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 05f05f17a7c2..9f0681bf1e87 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,10 +111,9 @@ 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 + * unlock() needs release semantics: */ - smp_mb__before_atomic(); - atomic_sub(_Q_LOCKED_VAL, &lock->val); + (void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val); } #endif |