From ab3f02fc237211f0583c1e7ba3bf504747be9b8d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 12 May 2015 10:52:27 +0200 Subject: [PATCH] locking/arch: Add WRITE_ONCE() to set_mb() Since we assume set_mb() to result in a single store followed by a full memory barrier, employ WRITE_ONCE(). Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/arm/include/asm/barrier.h | 2 +- arch/arm64/include/asm/barrier.h | 2 +- arch/ia64/include/asm/barrier.h | 2 +- arch/metag/include/asm/barrier.h | 2 +- arch/mips/include/asm/barrier.h | 2 +- arch/powerpc/include/asm/barrier.h | 2 +- arch/s390/include/asm/barrier.h | 2 +- arch/sparc/include/asm/barrier_64.h | 2 +- arch/x86/include/asm/barrier.h | 2 +- arch/x86/um/asm/barrier.h | 2 +- include/asm-generic/barrier.h | 2 +- include/linux/compiler.h | 2 +- 12 files changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h index d2f81e6b8c1c..993150aea681 100644 --- a/arch/arm/include/asm/barrier.h +++ b/arch/arm/include/asm/barrier.h @@ -81,7 +81,7 @@ do { \ #define read_barrier_depends() do { } while(0) #define smp_read_barrier_depends() do { } while(0) -#define set_mb(var, value) do { var = value; smp_mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0) #define smp_mb__before_atomic() smp_mb() #define smp_mb__after_atomic() smp_mb() diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h index 71f19c4dc0de..ff7de78d01b8 100644 --- a/arch/arm64/include/asm/barrier.h +++ b/arch/arm64/include/asm/barrier.h @@ -114,7 +114,7 @@ do { \ #define read_barrier_depends() do { } while(0) #define smp_read_barrier_depends() do { } while(0) -#define set_mb(var, value) do { var = value; smp_mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0) #define nop() asm volatile("nop"); #define smp_mb__before_atomic() smp_mb() diff --git a/arch/ia64/include/asm/barrier.h b/arch/ia64/include/asm/barrier.h index f6769eb2bbf9..03117e7b2ab8 100644 --- a/arch/ia64/include/asm/barrier.h +++ b/arch/ia64/include/asm/barrier.h @@ -82,7 +82,7 @@ do { \ * acquire vs release semantics but we can't discuss this stuff with * Linus just yet. Grrr... */ -#define set_mb(var, value) do { (var) = (value); mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0) /* * The group barrier in front of the rsm & ssm are necessary to ensure diff --git a/arch/metag/include/asm/barrier.h b/arch/metag/include/asm/barrier.h index d703d8e26a65..97eb018a2933 100644 --- a/arch/metag/include/asm/barrier.h +++ b/arch/metag/include/asm/barrier.h @@ -84,7 +84,7 @@ static inline void fence(void) #define read_barrier_depends() do { } while (0) #define smp_read_barrier_depends() do { } while (0) -#define set_mb(var, value) do { var = value; smp_mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0) #define smp_store_release(p, v) \ do { \ diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h index 2b8bbbcb9be0..cff1bbdaa74a 100644 --- a/arch/mips/include/asm/barrier.h +++ b/arch/mips/include/asm/barrier.h @@ -113,7 +113,7 @@ #endif #define set_mb(var, value) \ - do { var = value; smp_mb(); } while (0) + do { WRITE_ONCE(var, value); smp_mb(); } while (0) #define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory") diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h index a3bf5be111ff..2a072e48780d 100644 --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h @@ -34,7 +34,7 @@ #define rmb() __asm__ __volatile__ ("sync" : : : "memory") #define wmb() __asm__ __volatile__ ("sync" : : : "memory") -#define set_mb(var, value) do { var = value; mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0) #ifdef __SUBARCH_HAS_LWSYNC # define SMPWMB LWSYNC diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h index 8d724718ec21..b66cd53d35fc 100644 --- a/arch/s390/include/asm/barrier.h +++ b/arch/s390/include/asm/barrier.h @@ -36,7 +36,7 @@ #define smp_mb__before_atomic() smp_mb() #define smp_mb__after_atomic() smp_mb() -#define set_mb(var, value) do { var = value; mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0) #define smp_store_release(p, v) \ do { \ diff --git a/arch/sparc/include/asm/barrier_64.h b/arch/sparc/include/asm/barrier_64.h index 76648941fea7..125fec7512f4 100644 --- a/arch/sparc/include/asm/barrier_64.h +++ b/arch/sparc/include/asm/barrier_64.h @@ -41,7 +41,7 @@ do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \ #define dma_wmb() wmb() #define set_mb(__var, __value) \ - do { __var = __value; membar_safe("#StoreLoad"); } while(0) + do { WRITE_ONCE(__var, __value); membar_safe("#StoreLoad"); } while(0) #ifdef CONFIG_SMP #define smp_mb() mb() diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h index 959e45b81fe2..9de5cde133a1 100644 --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -40,7 +40,7 @@ #define smp_mb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() -#define set_mb(var, value) do { var = value; barrier(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0) #endif /* SMP */ #define read_barrier_depends() do { } while (0) diff --git a/arch/x86/um/asm/barrier.h b/arch/x86/um/asm/barrier.h index 7e8a1a650435..cc0cb01f346d 100644 --- a/arch/x86/um/asm/barrier.h +++ b/arch/x86/um/asm/barrier.h @@ -39,7 +39,7 @@ #define smp_mb() barrier() #define smp_rmb() barrier() #define smp_wmb() barrier() -#define set_mb(var, value) do { var = value; barrier(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0) #define read_barrier_depends() do { } while (0) #define smp_read_barrier_depends() do { } while (0) diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index f5c40b0fadc2..3938716b44d7 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -67,7 +67,7 @@ #endif #ifndef set_mb -#define set_mb(var, value) do { (var) = (value); mb(); } while (0) +#define set_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0) #endif #ifndef smp_mb__before_atomic diff --git a/include/linux/compiler.h b/include/linux/compiler.h index a7c0941d10da..03e227ba481c 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -250,7 +250,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) #define WRITE_ONCE(x, val) \ - ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; }) + ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) #endif /* __KERNEL__ */