* [PATCH 2/24] make atomic_read() behave consistently on arm
@ 2007-08-09 13:30 Chris Snook
2007-08-09 16:06 ` Russell King
0 siblings, 1 reply; 2+ messages in thread
From: Chris Snook @ 2007-08-09 13:30 UTC (permalink / raw)
To: linux-kernel, linux-arch, torvalds
Cc: netdev, akpm, ak, heiko.carstens, davem, schwidefsky, wensong,
horms, wjiang, cfriesen, zlynx, rpjday, jesper.juhl
From: Chris Snook <csnook@redhat.com>
Purify volatile use for atomic_t on arm.
Signed-off-by: Chris Snook <csnook@redhat.com>
--- 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
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH 2/24] make atomic_read() behave consistently on arm
2007-08-09 13:30 [PATCH 2/24] make atomic_read() behave consistently on arm Chris Snook
@ 2007-08-09 16:06 ` Russell King
0 siblings, 0 replies; 2+ messages in thread
From: Russell King @ 2007-08-09 16:06 UTC (permalink / raw)
To: Chris Snook
Cc: linux-kernel, linux-arch, torvalds, netdev, akpm, ak,
heiko.carstens, davem, schwidefsky, wensong, horms, wjiang,
cfriesen, zlynx, rpjday, jesper.juhl
On Thu, Aug 09, 2007 at 09:30:28AM -0400, Chris Snook wrote:
> From: Chris Snook <csnook@redhat.com>
>
> Purify volatile use for atomic_t on arm.
>
> Signed-off-by: Chris Snook <csnook@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
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