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authorPan Xinhui <xinhui.pan@linux.vnet.ibm.com>2016-06-03 11:38:14 +0300
committerIngo Molnar <mingo@kernel.org>2016-06-08 16:17:01 +0300
commitca50e426f96c905e7d14a9c7a6bd4e0330516047 (patch)
treee21ab5d1ec87777e8ebdf3d599de233648bc570b /include/asm-generic
parent6428671bae97caa7040e24e79e969fd87908f4f3 (diff)
downloadlinux-ca50e426f96c905e7d14a9c7a6bd4e0330516047.tar.xz
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>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/qspinlock.h5
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