2007-08-09 13:31:22

by Chris Snook

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

From: Chris Snook <[email protected]>

Purify volatile use for atomic_t on arm.

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

--- 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

2007-08-09 16:09:48

by Russell King

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

On Thu, Aug 09, 2007 at 09:30:28AM -0400, Chris Snook wrote:
> From: Chris Snook <[email protected]>
>
> Purify volatile use for atomic_t on arm.
>
> Signed-off-by: Chris Snook <[email protected]>

Acked-by: Russell King <[email protected]>

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: