[PATCH 18/24] make atomic_read() behave consistently on sh

From: Chris Snook
Date: Thu Aug 09 2007 - 10:11:27 EST


From: Chris Snook <csnook@xxxxxxxxxx>

Purify volatile use for atomic_t on sh.

Signed-off-by: Chris Snook <csnook@xxxxxxxxxx>

--- linux-2.6.23-rc2-orig/include/asm-sh/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-sh/atomic.h 2007-08-09 07:21:33.000000000 -0400
@@ -7,11 +7,15 @@
*
*/

-typedef struct { volatile int counter; } atomic_t;
+typedef struct { int counter; } atomic_t;

#define ATOMIC_INIT(i) ( (atomic_t) { (i) } )

-#define atomic_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 atomic_set(v,i) ((v)->counter = (i))

#include <linux/compiler.h>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/