From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Cc: arnd@arndb.de, peterz@infradead.org, waiman.long@hp.com,
Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Subject: [PATCH] locking/qspinlock: Use atomic_sub_return_release in queued_spin_unlock
Date: Fri, 3 Jun 2016 16:38:14 +0800 [thread overview]
Message-ID: <1464943094-3129-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> (raw)
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>
---
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
next reply other threads:[~2016-06-03 8:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-03 8:38 Pan Xinhui [this message]
2016-06-08 14:27 ` [tip:locking/core] locking/qspinlock: Use atomic_sub_return_release() in queued_spin_unlock() tip-bot for Pan Xinhui
2016-06-13 19:45 ` [PATCH] locking/qspinlock: Use atomic_sub_return_release in queued_spin_unlock Davidlohr Bueso
2016-06-14 5:52 ` Boqun Feng
2016-06-14 12:04 ` Peter Zijlstra
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