On Fri, 19 Oct 2007, Nick Piggin wrote:
> Of course, we can avoid the fence altogether on x86 as well, because
> it simply isn't needed for release semantics.
So we can generally switch to using wmb there?
__clear_bit_unlock: A write barrier is sufficient for release semantics
Switch the smb_mb that causes a fence instruction to be issued on x86
to a write barrier which issues no instruction on x86.
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Index: linux-2.6/include/asm-generic/bitops/lock.h
===================================================================
--- linux-2.6.orig/include/asm-generic/bitops/lock.h 2007-10-19 04:08:58.000000000 -0700
+++ linux-2.6/include/asm-generic/bitops/lock.h 2007-10-19 04:09:17.000000000 -0700
@@ -37,7 +37,7 @@ do { \
*/
#define __clear_bit_unlock(nr, addr) \
do { \
- smp_mb(); \
+ smp_wmb(); \
__clear_bit(nr, addr); \
} while (0)
-
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