[ARM] 4241/1: Define mb() as compiler barrier on a uniprocessor system

Currently, the mb() is defined as a DMB operation on ARMv6, even for
UP systems. This patch defines mb() as a compiler barrier only. For
the SMP case, the smp_* variants should be used anyway and the patch
defines them as DMB.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 19 insertions, 21 deletions

diff --git a/include/asm-arm/system.h b/include/asm-arm/system.h
index f4386906b200..f06d8a43fdee 100644
--- a/include/asm-arm/system.h
+++ b/include/asm-arm/system.h
@@ -167,11 +167,25 @@ extern unsigned int user_debug;
                                     : : "r" (0) : "memory")
 #define dmb() __asm__ __volatile__ ("" : : : "memory")
 #endif
-#define mb() dmb()
-#define rmb() mb()
-#define wmb() mb()
-#define read_barrier_depends() do { } while(0)
-#define set_mb(var, value)  do { var = value; mb(); } while (0)
+
+#define mb()                    barrier()
+#define rmb()                   barrier()
+#define wmb()                   barrier()
+#define read_barrier_depends()  do { } while(0)
+
+#ifdef CONFIG_SMP
+#define smp_mb()                dmb()
+#define smp_rmb()               dmb()
+#define smp_wmb()               dmb()
+#define smp_read_barrier_depends()      read_barrier_depends()
+#else
+#define smp_mb()                barrier()
+#define smp_rmb()               barrier()
+#define smp_wmb()               barrier()
+#define smp_read_barrier_depends()      read_barrier_depends()
+#endif /* CONFIG_SMP */
+
+#define set_mb(var, value)      do { var = value; smp_mb(); } while (0)
 #define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
 
 extern unsigned long cr_no_alignment;   /* defined in entry-armv.S */
@@ -243,22 +257,6 @@ static inline void sched_cacheflush(void)
 {
 }
 
-#ifdef CONFIG_SMP
-
-#define smp_mb()                mb()
-#define smp_rmb()               rmb()
-#define smp_wmb()               wmb()
-#define smp_read_barrier_depends()              read_barrier_depends()
-
-#else
-
-#define smp_mb()                barrier()
-#define smp_rmb()               barrier()
-#define smp_wmb()               barrier()
-#define smp_read_barrier_depends()              do { } while(0)
-
-#endif /* CONFIG_SMP */
-
 #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
 /*
  * On the StrongARM, "swp" is terminally broken since it bypasses the