From ce332f662deb545c8a4f3f58debcca26bb2e44b0 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Mon, 4 Nov 2013 22:36:17 +0200 Subject: [PATCH] srcu: API for barrier after srcu read unlock srcu read lock/unlock include a full memory barrier but that's an implementation detail. Add an API for make memory fencing explicit for users that need this barrier, to make sure we can change it as needed without breaking all users. Acked-by: "Paul E. McKenney" Reviewed-by: Paul E. McKenney Signed-off-by: Michael S. Tsirkin Signed-off-by: Gleb Natapov --- include/linux/srcu.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index c114614..9b058ee 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -237,4 +237,18 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) __srcu_read_unlock(sp, idx); } +/** + * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock + * + * Converts the preceding srcu_read_unlock into a two-way memory barrier. + * + * Call this after srcu_read_unlock, to guarantee that all memory operations + * that occur after smp_mb__after_srcu_read_unlock will appear to happen after + * the preceding srcu_read_unlock. + */ +static inline void smp_mb__after_srcu_read_unlock(void) +{ + /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ +} + #endif -- 2.7.4