Subject: [PATCH 2/24] make atomic_read() behave consistently on arm

From: Chris Snook <[email-masked]>
Date: Thu, 9 Aug 2007 09:30:28 -0400

From: Chris Snook <[email-masked]>

Purify volatile use for atomic_t on arm.

Signed-off-by: Chris Snook <[email-masked]>

--- linux-2.6.23-rc2-orig/include/asm-arm/atomic.h	2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-arm/atomic.h	2007-08-09 06:30:40.000000000 -0400
@@ -14,13 +14,17 @@
 #include <linux/compiler.h>
 #include <asm/system.h>
 
-typedef struct { volatile int counter; } atomic_t;
+typedef struct { int counter; } atomic_t;
 
 #define ATOMIC_INIT(i)	{ (i) }
 
 #ifdef __KERNEL__
 
-#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)
 
 #if __LINUX_ARM_ARCH__ >= 6