From d85b62f18d543c663cbdd6061054efeb9e66cee7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 28 Nov 2016 12:08:49 -0800 Subject: srcu: Force full grace-period ordering If a process invokes synchronize_srcu(), is delayed just the right amount of time, and thus does not sleep when waiting for the grace period to complete, there is no ordering between the end of the grace period and the code following the synchronize_srcu(). Similarly, there can be a lack of ordering between the end of the SRCU grace period and callback invocation. This commit adds the necessary ordering. Reported-by: Lance Roy Signed-off-by: Paul E. McKenney [ paulmck: Further smp_mb() adjustment per email with Lance Roy. ] --- include/linux/rcupdate.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 01f71e1d2e94..6ade6a52d9d4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1161,5 +1161,17 @@ do { \ ftrace_dump(oops_dump_mode); \ } while (0) +/* + * Place this after a lock-acquisition primitive to guarantee that + * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies + * if the UNLOCK and LOCK are executed by the same CPU or if the + * UNLOCK and LOCK operate on the same lock variable. + */ +#ifdef CONFIG_PPC +#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ +#else /* #ifdef CONFIG_PPC */ +#define smp_mb__after_unlock_lock() do { } while (0) +#endif /* #else #ifdef CONFIG_PPC */ + #endif /* __LINUX_RCUPDATE_H */ -- cgit v1.2.3