[PATCH 19/24] make atomic_read() behave consistently on sparc64
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From: Chris Snook <hidden>
Date: 2007-08-09 14:13:42
Also in:
linux-arch, lkml
From: Chris Snook <redacted> Purify volatile use for atomic[64]_t on sparc64. Signed-off-by: Chris Snook <redacted>
--- linux-2.6.23-rc2-orig/include/asm-sparc64/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-sparc64/atomic.h 2007-08-09 07:48:01.000000000 -0400@@ -11,14 +11,18 @@ #include <linux/types.h> #include <asm/system.h> -typedef struct { volatile int counter; } atomic_t; -typedef struct { volatile __s64 counter; } atomic64_t; +typedef struct { int counter; } atomic_t; +typedef struct { __s64 counter; } atomic64_t; #define ATOMIC_INIT(i) { (i) } #define ATOMIC64_INIT(i) { (i) } -#define atomic_read(v) ((v)->counter) -#define atomic64_read(v) ((v)->counter) +/* + * Casting to volatile here minimizes the need for barriers, + * without having to declare the type itself as volatile. + */ +#define atomic_read(v) (*(volatile int *)&(v)->counter) +#define atomic64_read(v) (*(volatile __s64 *)&(v)->counter) #define atomic_set(v, i) (((v)->counter) = i) #define atomic64_set(v, i) (((v)->counter) = i)