[PATCH 9/24] make atomic_read() behave consistently on ia64
From: Chris Snook <hidden>
Date: 2007-08-09 13:51:48
Also in:
linux-arch, lkml
From: Chris Snook <redacted> Purify volatile use for atomic[64]_t on ia64. Signed-off-by: Chris Snook <redacted>
--- linux-2.6.23-rc2-orig/include/asm-ia64/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-ia64/atomic.h 2007-08-09 06:53:48.000000000 -0400@@ -17,18 +17,18 @@ #include <asm/intrinsics.h> #include <asm/system.h> -/* - * On IA-64, counter must always be volatile to ensure that that the - * memory accesses are ordered. - */ -typedef struct { volatile __s32 counter; } atomic_t; -typedef struct { volatile __s64 counter; } atomic64_t; +typedef struct { __s32 counter; } atomic_t; +typedef struct { __s64 counter; } atomic64_t; #define ATOMIC_INIT(i) ((atomic_t) { (i) }) #define ATOMIC64_INIT(i) ((atomic64_t) { (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 __s32 *)&(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))