From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753760Ab3KCPRb (ORCPT ); Sun, 3 Nov 2013 10:17:31 -0500 Received: from merlin.infradead.org ([205.233.59.134]:48247 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752603Ab3KCPR3 (ORCPT ); Sun, 3 Nov 2013 10:17:29 -0500 Date: Sun, 3 Nov 2013 16:17:04 +0100 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Victor Kaplansky , Oleg Nesterov , Anton Blanchard , Benjamin Herrenschmidt , Frederic Weisbecker , LKML , Linux PPC dev , Mathieu Desnoyers , Michael Ellerman , Michael Neuling , Linus Torvalds Subject: [RFC] arch: Introduce new TSO memory barrier smp_tmb() Message-ID: <20131103151704.GJ19466@laptop.lan> References: <20131028132634.GO19466@laptop.lan> <20131028163418.GD4126@linux.vnet.ibm.com> <20131028201735.GA15629@redhat.com> <20131030092725.GL4126@linux.vnet.ibm.com> <20131030112526.GI16117@laptop.programming.kicks-ass.net> <20131031064015.GV4126@linux.vnet.ibm.com> <20131101145634.GH19466@laptop.lan> <20131102173239.GB3947@linux.vnet.ibm.com> <20131103144017.GA25118@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131103144017.GA25118@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) X-Bad-Reply: References and In-Reply-To but no 'Re:' in Subject. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 03, 2013 at 06:40:17AM -0800, Paul E. McKenney wrote: > If there was an smp_tmb(), I would likely use it in rcu_assign_pointer(). Well, I'm obviously all for introducing this new barrier, for it will reduce a full mfence on x86 to a compiler barrier. And ppc can use lwsync as opposed to sync afaict. Not sure ARM can do better. --- Subject: arch: Introduce new TSO memory barrier smp_tmb() A few sites could be downgraded from smp_mb() to smp_tmb() and a few site should be upgraded to smp_tmb() that are now using smp_wmb(). XXX hope PaulMck explains things better.. X86 (!OOSTORE), SPARC have native TSO memory models and smp_tmb() reduces to barrier(). PPC can use lwsync instead of sync For the other archs, have smp_tmb map to smp_mb, as the stronger barrier is always correct but possibly suboptimal. Suggested-by: Paul McKenney Not-Signed-off-by: Peter Zijlstra --- arch/alpha/include/asm/barrier.h | 2 ++ arch/arc/include/asm/barrier.h | 2 ++ arch/arm/include/asm/barrier.h | 2 ++ arch/arm64/include/asm/barrier.h | 2 ++ arch/avr32/include/asm/barrier.h | 1 + arch/blackfin/include/asm/barrier.h | 1 + arch/cris/include/asm/barrier.h | 2 ++ arch/frv/include/asm/barrier.h | 1 + arch/h8300/include/asm/barrier.h | 2 ++ arch/hexagon/include/asm/barrier.h | 1 + arch/ia64/include/asm/barrier.h | 2 ++ arch/m32r/include/asm/barrier.h | 2 ++ arch/m68k/include/asm/barrier.h | 1 + arch/metag/include/asm/barrier.h | 3 +++ arch/microblaze/include/asm/barrier.h | 1 + arch/mips/include/asm/barrier.h | 3 +++ arch/mn10300/include/asm/barrier.h | 2 ++ arch/parisc/include/asm/barrier.h | 1 + arch/powerpc/include/asm/barrier.h | 2 ++ arch/s390/include/asm/barrier.h | 1 + arch/score/include/asm/barrier.h | 1 + arch/sh/include/asm/barrier.h | 2 ++ arch/sparc/include/asm/barrier_32.h | 1 + arch/sparc/include/asm/barrier_64.h | 3 +++ arch/tile/include/asm/barrier.h | 2 ++ arch/unicore32/include/asm/barrier.h | 1 + arch/x86/include/asm/barrier.h | 3 +++ arch/xtensa/include/asm/barrier.h | 1 + 28 files changed, 48 insertions(+) diff --git a/arch/alpha/include/asm/barrier.h b/arch/alpha/include/asm/barrier.h index ce8860a0b32d..02ea63897038 100644 --- a/arch/alpha/include/asm/barrier.h +++ b/arch/alpha/include/asm/barrier.h @@ -18,12 +18,14 @@ __asm__ __volatile__("mb": : :"memory") #ifdef CONFIG_SMP #define __ASM_SMP_MB "\tmb\n" #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #else #define __ASM_SMP_MB #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while (0) diff --git a/arch/arc/include/asm/barrier.h b/arch/arc/include/asm/barrier.h index f6cb7c4ffb35..456c790fa1ad 100644 --- a/arch/arc/include/asm/barrier.h +++ b/arch/arc/include/asm/barrier.h @@ -22,10 +22,12 @@ /* TODO-vineetg verify the correctness of macros here */ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #endif diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h index 60f15e274e6d..bc88a8505673 100644 --- a/arch/arm/include/asm/barrier.h +++ b/arch/arm/include/asm/barrier.h @@ -51,10 +51,12 @@ #ifndef CONFIG_SMP #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #else #define smp_mb() dmb(ish) +#define smp_tmb() smp_mb() #define smp_rmb() smp_mb() #define smp_wmb() dmb(ishst) #endif diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h index d4a63338a53c..ec0531f4892f 100644 --- a/arch/arm64/include/asm/barrier.h +++ b/arch/arm64/include/asm/barrier.h @@ -33,10 +33,12 @@ #ifndef CONFIG_SMP #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #else #define smp_mb() asm volatile("dmb ish" : : : "memory") +#define smp_tmb() asm volatile("dmb ish" : : : "memory") #define smp_rmb() asm volatile("dmb ishld" : : : "memory") #define smp_wmb() asm volatile("dmb ishst" : : : "memory") #endif diff --git a/arch/avr32/include/asm/barrier.h b/arch/avr32/include/asm/barrier.h index 0961275373db..6c6ccb9cf290 100644 --- a/arch/avr32/include/asm/barrier.h +++ b/arch/avr32/include/asm/barrier.h @@ -20,6 +20,7 @@ # error "The AVR32 port does not support SMP" #else # define smp_mb() barrier() +# define smp_tmb() barrier() # define smp_rmb() barrier() # define smp_wmb() barrier() # define smp_read_barrier_depends() do { } while(0) diff --git a/arch/blackfin/include/asm/barrier.h b/arch/blackfin/include/asm/barrier.h index ebb189507dd7..100f49121a18 100644 --- a/arch/blackfin/include/asm/barrier.h +++ b/arch/blackfin/include/asm/barrier.h @@ -40,6 +40,7 @@ #endif /* !CONFIG_SMP */ #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define set_mb(var, value) do { var = value; mb(); } while (0) diff --git a/arch/cris/include/asm/barrier.h b/arch/cris/include/asm/barrier.h index 198ad7fa6b25..679c33738b4c 100644 --- a/arch/cris/include/asm/barrier.h +++ b/arch/cris/include/asm/barrier.h @@ -12,11 +12,13 @@ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/frv/include/asm/barrier.h b/arch/frv/include/asm/barrier.h index 06776ad9f5e9..60354ce13ba0 100644 --- a/arch/frv/include/asm/barrier.h +++ b/arch/frv/include/asm/barrier.h @@ -20,6 +20,7 @@ #define read_barrier_depends() do { } while (0) #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do {} while(0) diff --git a/arch/h8300/include/asm/barrier.h b/arch/h8300/include/asm/barrier.h index 9e0aa9fc195d..e8e297fa4e9a 100644 --- a/arch/h8300/include/asm/barrier.h +++ b/arch/h8300/include/asm/barrier.h @@ -16,11 +16,13 @@ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/hexagon/include/asm/barrier.h b/arch/hexagon/include/asm/barrier.h index 1041a8e70ce8..2dd5b2ad4d21 100644 --- a/arch/hexagon/include/asm/barrier.h +++ b/arch/hexagon/include/asm/barrier.h @@ -28,6 +28,7 @@ #define smp_rmb() barrier() #define smp_read_barrier_depends() barrier() #define smp_wmb() barrier() +#define smp_tmb() barrier() #define smp_mb() barrier() #define smp_mb__before_atomic_dec() barrier() #define smp_mb__after_atomic_dec() barrier() diff --git a/arch/ia64/include/asm/barrier.h b/arch/ia64/include/asm/barrier.h index 60576e06b6fb..a5f92146b091 100644 --- a/arch/ia64/include/asm/barrier.h +++ b/arch/ia64/include/asm/barrier.h @@ -42,11 +42,13 @@ #ifdef CONFIG_SMP # define smp_mb() mb() +# define smp_tmb() mb() # define smp_rmb() rmb() # define smp_wmb() wmb() # define smp_read_barrier_depends() read_barrier_depends() #else # define smp_mb() barrier() +# define smp_tmb() barrier() # define smp_rmb() barrier() # define smp_wmb() barrier() # define smp_read_barrier_depends() do { } while(0) diff --git a/arch/m32r/include/asm/barrier.h b/arch/m32r/include/asm/barrier.h index 6976621efd3f..a6fa29facd7a 100644 --- a/arch/m32r/include/asm/barrier.h +++ b/arch/m32r/include/asm/barrier.h @@ -79,12 +79,14 @@ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #define set_mb(var, value) do { (void) xchg(&var, value); } while (0) #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while (0) diff --git a/arch/m68k/include/asm/barrier.h b/arch/m68k/include/asm/barrier.h index 445ce22c23cb..8ecf52c87847 100644 --- a/arch/m68k/include/asm/barrier.h +++ b/arch/m68k/include/asm/barrier.h @@ -13,6 +13,7 @@ #define set_mb(var, value) ({ (var) = (value); wmb(); }) #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() ((void)0) diff --git a/arch/metag/include/asm/barrier.h b/arch/metag/include/asm/barrier.h index c90bfc6bf648..eb179fbce580 100644 --- a/arch/metag/include/asm/barrier.h +++ b/arch/metag/include/asm/barrier.h @@ -50,6 +50,7 @@ static inline void wmb(void) #ifndef CONFIG_SMP #define fence() do { } while (0) #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #else @@ -70,11 +71,13 @@ static inline void fence(void) *flushptr = 0; } #define smp_mb() fence() +#define smp_tmb() fence() #define smp_rmb() fence() #define smp_wmb() barrier() #else #define fence() do { } while (0) #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #endif diff --git a/arch/microblaze/include/asm/barrier.h b/arch/microblaze/include/asm/barrier.h index df5be3e87044..d573c170a717 100644 --- a/arch/microblaze/include/asm/barrier.h +++ b/arch/microblaze/include/asm/barrier.h @@ -21,6 +21,7 @@ #define set_wmb(var, value) do { var = value; wmb(); } while (0) #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h index 314ab5532019..535e699eec3b 100644 --- a/arch/mips/include/asm/barrier.h +++ b/arch/mips/include/asm/barrier.h @@ -144,15 +144,18 @@ #if defined(CONFIG_WEAK_ORDERING) && defined(CONFIG_SMP) # ifdef CONFIG_CPU_CAVIUM_OCTEON # define smp_mb() __sync() +# define smp_tmb() __sync() # define smp_rmb() barrier() # define smp_wmb() __syncw() # else # define smp_mb() __asm__ __volatile__("sync" : : :"memory") +# define smp_tmb() __asm__ __volatile__("sync" : : :"memory") # define smp_rmb() __asm__ __volatile__("sync" : : :"memory") # define smp_wmb() __asm__ __volatile__("sync" : : :"memory") # endif #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #endif diff --git a/arch/mn10300/include/asm/barrier.h b/arch/mn10300/include/asm/barrier.h index 2bd97a5c8af7..a345b0776e5f 100644 --- a/arch/mn10300/include/asm/barrier.h +++ b/arch/mn10300/include/asm/barrier.h @@ -19,11 +19,13 @@ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define set_mb(var, value) do { xchg(&var, value); } while (0) #else /* CONFIG_SMP */ #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define set_mb(var, value) do { var = value; mb(); } while (0) diff --git a/arch/parisc/include/asm/barrier.h b/arch/parisc/include/asm/barrier.h index e77d834aa803..f53196b589ec 100644 --- a/arch/parisc/include/asm/barrier.h +++ b/arch/parisc/include/asm/barrier.h @@ -25,6 +25,7 @@ #define rmb() mb() #define wmb() mb() #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() mb() #define smp_wmb() mb() #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h index ae782254e731..d7e8a560f1fe 100644 --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h @@ -46,11 +46,13 @@ #endif #define smp_mb() mb() +#define smp_tmb() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") #define smp_rmb() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") #define smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory") #define smp_read_barrier_depends() read_barrier_depends() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h index 16760eeb79b0..f0409a874243 100644 --- a/arch/s390/include/asm/barrier.h +++ b/arch/s390/include/asm/barrier.h @@ -24,6 +24,7 @@ #define wmb() mb() #define read_barrier_depends() do { } while(0) #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() diff --git a/arch/score/include/asm/barrier.h b/arch/score/include/asm/barrier.h index 0eacb6471e6d..865652083dde 100644 --- a/arch/score/include/asm/barrier.h +++ b/arch/score/include/asm/barrier.h @@ -5,6 +5,7 @@ #define rmb() barrier() #define wmb() barrier() #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() diff --git a/arch/sh/include/asm/barrier.h b/arch/sh/include/asm/barrier.h index 72c103dae300..f8dce7926432 100644 --- a/arch/sh/include/asm/barrier.h +++ b/arch/sh/include/asm/barrier.h @@ -39,11 +39,13 @@ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/sparc/include/asm/barrier_32.h b/arch/sparc/include/asm/barrier_32.h index c1b76654ee76..1037ce189cee 100644 --- a/arch/sparc/include/asm/barrier_32.h +++ b/arch/sparc/include/asm/barrier_32.h @@ -8,6 +8,7 @@ #define read_barrier_depends() do { } while(0) #define set_mb(__var, __value) do { __var = __value; mb(); } while(0) #define smp_mb() __asm__ __volatile__("":::"memory") +#define smp_tmb() __asm__ __volatile__("":::"memory") #define smp_rmb() __asm__ __volatile__("":::"memory") #define smp_wmb() __asm__ __volatile__("":::"memory") #define smp_read_barrier_depends() do { } while(0) diff --git a/arch/sparc/include/asm/barrier_64.h b/arch/sparc/include/asm/barrier_64.h index 95d45986f908..0f3c2fdb86b8 100644 --- a/arch/sparc/include/asm/barrier_64.h +++ b/arch/sparc/include/asm/barrier_64.h @@ -34,6 +34,7 @@ do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \ * memory ordering than required by the specifications. */ #define mb() membar_safe("#StoreLoad") +#define tmb() __asm__ __volatile__("":::"memory") #define rmb() __asm__ __volatile__("":::"memory") #define wmb() __asm__ __volatile__("":::"memory") @@ -43,10 +44,12 @@ do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \ #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() tmb() #define smp_rmb() rmb() #define smp_wmb() wmb() #else #define smp_mb() __asm__ __volatile__("":::"memory") +#define smp_tmb() __asm__ __volatile__("":::"memory") #define smp_rmb() __asm__ __volatile__("":::"memory") #define smp_wmb() __asm__ __volatile__("":::"memory") #endif diff --git a/arch/tile/include/asm/barrier.h b/arch/tile/include/asm/barrier.h index a9a73da5865d..cad3c6ae28bf 100644 --- a/arch/tile/include/asm/barrier.h +++ b/arch/tile/include/asm/barrier.h @@ -127,11 +127,13 @@ mb_incoherent(void) #ifdef CONFIG_SMP #define smp_mb() mb() +#define smp_tmb() mb() #define smp_rmb() rmb() #define smp_wmb() wmb() #define smp_read_barrier_depends() read_barrier_depends() #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while (0) diff --git a/arch/unicore32/include/asm/barrier.h b/arch/unicore32/include/asm/barrier.h index a6620e5336b6..8b341fffbda6 100644 --- a/arch/unicore32/include/asm/barrier.h +++ b/arch/unicore32/include/asm/barrier.h @@ -18,6 +18,7 @@ #define rmb() barrier() #define wmb() barrier() #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define read_barrier_depends() do { } while (0) diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h index c6cd358a1eec..480201d83af1 100644 --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -86,14 +86,17 @@ # define smp_rmb() barrier() #endif #ifdef CONFIG_X86_OOSTORE +# define smp_tmb() mb() # define smp_wmb() wmb() #else +# define smp_tmb() barrier() # define smp_wmb() barrier() #endif #define smp_read_barrier_depends() read_barrier_depends() #define set_mb(var, value) do { (void)xchg(&var, value); } while (0) #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #define smp_read_barrier_depends() do { } while (0) diff --git a/arch/xtensa/include/asm/barrier.h b/arch/xtensa/include/asm/barrier.h index ef021677d536..7839db843ea5 100644 --- a/arch/xtensa/include/asm/barrier.h +++ b/arch/xtensa/include/asm/barrier.h @@ -20,6 +20,7 @@ #error smp_* not defined #else #define smp_mb() barrier() +#define smp_tmb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() #endif