Re: [PATCH v2 tip/core/rcu 02/39] rcu: Make arch select smp_mb__after_unlock_lock() strength
From: Josh Triplett <josh@joshtriplett.org>
Date: 2017-04-18 00:19:47
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On Mon, Apr 17, 2017 at 04:44:49PM -0700, Paul E. McKenney wrote:
The definition of smp_mb__after_unlock_lock() is currently smp_mb() for CONFIG_PPC and a no-op otherwise. It would be better to instead provide an architecture-selectable Kconfig option, and select the strength of smp_mb__after_unlock_lock() based on that option. This commit therefore creates ARCH_WEAK_RELEASE_ACQUIRE, has PPC select it, and bases the definition of smp_mb__after_unlock_lock() on this new ARCH_WEAK_RELEASE_ACQUIRE Kconfig option. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <redacted> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <redacted> Cc: Boqun Feng <redacted> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <redacted> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: <redacted>
Seems sensible. Reviewed-by: Josh Triplett <josh@joshtriplett.org>
quoted hunk ↗ jump to hunk
arch/Kconfig | 3 +++ arch/powerpc/Kconfig | 1 + include/linux/rcupdate.h | 6 +++--- 3 files changed, 7 insertions(+), 3 deletions(-)diff --git a/arch/Kconfig b/arch/Kconfig index cd211a14a88f..adefaf344239 100644 --- a/arch/Kconfig +++ b/arch/Kconfig@@ -320,6 +320,9 @@ config HAVE_CMPXCHG_LOCAL config HAVE_CMPXCHG_DOUBLE bool +config ARCH_WEAK_RELEASE_ACQUIRE + bool + config ARCH_WANT_IPC_PARSE_VERSION booldiff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 97a8bc8a095c..7a5c9b764cd2 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig@@ -99,6 +99,7 @@ config PPC select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if PPC64 select ARCH_WANT_IPC_PARSE_VERSION + select ARCH_WEAK_RELEASE_ACQUIRE select BINFMT_ELF select BUILDTIME_EXTABLE_SORT select CLONE_BACKWARDSdiff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index de88b33c0974..e6146d0074f8 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h@@ -1127,11 +1127,11 @@ do { \ * 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 +#ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE #define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ -#else /* #ifdef CONFIG_PPC */ +#else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ #define smp_mb__after_unlock_lock() do { } while (0) -#endif /* #else #ifdef CONFIG_PPC */ +#endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ #endif /* __LINUX_RCUPDATE_H */-- 2.5.2