[patch 21/28] Add cmpxchg_local to ppc

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

Add a local processor version of cmpxchg for ppc.

Implements __cmpxchg_u32_local and uses it for 32 bits cmpxchg_local.
It uses the non NMI safe cmpxchg_local_generic for 1, 2 and 8 bytes
cmpxchg_local.

From: Gunnar Larisch <gl@denx.de>
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Gunnar Larisch <gl@denx.de>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: clameter@sgi.com
CC: benh@kernel.crashing.org
---
 include/asm-ppc/system.h |   51 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

Index: linux-2.6-lttng/include/asm-ppc/system.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-ppc/system.h	2007-10-31 17:32:43.000000000 -0400
+++ linux-2.6-lttng/include/asm-ppc/system.h	2007-10-31 18:24:26.000000000 -0400
@@ -208,12 +208,34 @@ __cmpxchg_u32(volatile unsigned int *p, 
 	return prev;
 }
 
+static __inline__ unsigned long
+__cmpxchg_u32_local(volatile unsigned int *p, unsigned int old,
+	unsigned int new)
+{
+	unsigned int prev;
+
+	__asm__ __volatile__ ("\n\
+1:	lwarx	%0,0,%2 \n\
+	cmpw	0,%0,%3 \n\
+	bne	2f \n"
+	PPC405_ERR77(0,%2)
+"	stwcx.	%4,0,%2 \n\
+	bne-	1b\n"
+"2:"
+	: "=&r" (prev), "=m" (*p)
+	: "r" (p), "r" (old), "r" (new), "m" (*p)
+	: "cc", "memory");
+
+	return prev;
+}
+
 /* This function doesn't exist, so you'll get a linker error
    if something tries to do an invalid cmpxchg().  */
 extern void __cmpxchg_called_with_bad_pointer(void);
 
 static __inline__ unsigned long
-__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
+__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new,
+	unsigned int size)
 {
 	switch (size) {
 	case 4:
@@ -227,7 +249,7 @@ __cmpxchg(volatile void *ptr, unsigned l
 	return old;
 }
 
-#define cmpxchg(ptr,o,n)						 \
+#define cmpxchg(ptr, o, n)						 \
   ({									 \
      __typeof__(*(ptr)) _o_ = (o);					 \
      __typeof__(*(ptr)) _n_ = (n);					 \
@@ -235,6 +257,31 @@ __cmpxchg(volatile void *ptr, unsigned l
 				    (unsigned long)_n_, sizeof(*(ptr))); \
   })
 
+#include <asm-generic/cmpxchg-local.h>
+
+static inline unsigned long __cmpxchg_local(volatile void *ptr,
+				      unsigned long old,
+				      unsigned long new, int size)
+{
+	switch (size) {
+	case 4:
+		return __cmpxchg_u32_local(ptr, old, new);
+	default:
+		return __cmpxchg_local_generic(ptr, old, new, size);
+	}
+
+	return old;
+}
+
+/*
+ * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
+ * them available.
+ */
+#define cmpxchg_local(ptr, o, n)				  	\
+	((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o),	\
+			(unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
+
 #define arch_align_stack(x) (x)
 
 #endif /* __KERNEL__ */

-- 
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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