From 33940d09937276cd3c81f2874faf43e37c2db0e2 Mon Sep 17 00:00:00 2001 From: Joern Engel Date: Tue, 16 Sep 2014 16:23:12 -0400 Subject: target: encapsulate smp_mb__after_atomic() The target code has a rather generous helping of smp_mb__after_atomic() throughout the code base. Most atomic operations were followed by one and none were preceded by smp_mb__before_atomic(), nor accompanied by a comment explaining the need for a barrier. Instead of trying to prove for every case whether or not it is needed, this patch introduces atomic_inc_mb() and atomic_dec_mb(), which explicitly include the memory barriers before and after the atomic operation. For now they are defined in a target header, although they could be of general use. Most of the existing atomic/mb combinations were replaced by the new helpers. In a few cases the atomic was sandwiched in spin_lock/spin_unlock and I simply removed the barrier. I suspect that in most cases the correct conversion would have been to drop the barrier. I also suspect that a few cases exist where a) the barrier was necessary and b) a second barrier before the atomic would have been necessary and got added by this patch. Signed-off-by: Joern Engel Signed-off-by: Nicholas Bellinger --- include/target/target_core_base.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/target') diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 9ec9864ecf38..b106240d8385 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -903,4 +903,18 @@ struct se_wwn { struct config_group fabric_stat_group; }; +static inline void atomic_inc_mb(atomic_t *v) +{ + smp_mb__before_atomic(); + atomic_inc(v); + smp_mb__after_atomic(); +} + +static inline void atomic_dec_mb(atomic_t *v) +{ + smp_mb__before_atomic(); + atomic_dec(v); + smp_mb__after_atomic(); +} + #endif /* TARGET_CORE_BASE_H */ -- cgit v1.2.3-59-g8ed1b