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) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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__ */