[PATCH] define have_arch_cmpxchg()

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

define have_arch_cmpxchg()

* Christoph Lameter (clameter@sgi.com) wrote:
> If we really want to do this then the implementation of all of these 
> components need to result in competitive performance on all platforms.
> 
Here is the first of 2 proposed patches to keep the same performances on
architectures that does not implement cmpxchg_local.

Add have_arch_cmpxchg(), which can be used within the body of functions to
select between irq disable and local_cmpxchg.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
 include/linux/hardirq.h |    6 ++++++
 1 file changed, 6 insertions(+)

Index: slab/include/linux/hardirq.h
===================================================================
--- slab.orig/include/linux/hardirq.h	2007-08-22 10:27:07.000000000 -0400
+++ slab/include/linux/hardirq.h	2007-08-22 10:27:46.000000000 -0400
@@ -149,4 +149,10 @@ extern void irq_exit(void);
 #define nmi_enter()		do { lockdep_off(); __irq_enter(); } while (0)
 #define nmi_exit()		do { __irq_exit(); lockdep_on(); } while (0)
 
+#ifdef __HAVE_ARCH_CMPXCHG
+#define have_arch_cmpxchg()	1
+#else
+#define have_arch_cmpxchg()	0
+#endif
+
 #endif /* LINUX_HARDIRQ_H */

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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