Commit-ID: ca50e426f96c905e7d14a9c7a6bd4e0330516047 Gitweb: http://git.kernel.org/tip/ca50e426f96c905e7d14a9c7a6bd4e0330516047 Author: Pan Xinhui <xinhui....@linux.vnet.ibm.com> AuthorDate: Fri, 3 Jun 2016 16:38:14 +0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 8 Jun 2016 15:17:01 +0200
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) <pet...@infradead.org> Signed-off-by: Pan Xinhui <xinhui....@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: a...@arndb.de Cc: waiman.l...@hp.com Link: http://lkml.kernel.org/r/1464943094-3129-1-git-send-email-xinhui....@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- include/asm-generic/qspinlock.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 05f05f1..9f0681b 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
