[PATCH 9/24] make atomic_read() behave consistently on ia64

Chris Snook
2007-08-09T13:51:48Z

From: Chris Snook <csnook@redhat.com>

Purify volatile use for atomic[64]_t on ia64.

Signed-off-by: Chris Snook <csnook@redhat.com>

--- 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))