[PATCH] Cast cmpxchg and cmpxchg_local result for 386 and 486

[Mathieu Desnoyers]

Vegard Nossum <vegard.nossum@xxxxxxxxx> :
> Hi,
>
> I get these warnings when compiling mm/slub.c in linux-2.6.git:
>
> mm/slub.c: In function 'slab_alloc':
> mm/slub.c:1637: warning: assignment makes pointer from integer without a cast
> mm/slub.c:1637: warning: assignment makes pointer from integer without a cast
> mm/slub.c: In function 'slab_free':
> mm/slub.c:1796: warning: assignment makes pointer from integer without a cast
> mm/slub.c:1796: warning: assignment makes pointer from integer without a cast
>
> The actual lines are calls to cmpxchg_local(). This is probably
> because I'm compiling with M386. I'm guessing the source of the
> warnings is in include/asm-x86/cmpxchg_32.h, lines 283 and 286. Config
> attached.

Christoph Lameter <clameter@xxxxxxx>
Hmmm.. That cmpxchg local needs to be fixed? Mathieu?

Yes, a cast is needed in the 386 and 486 code because the type is a pointer. In
every other integer case the original cmpxchg code (and the cmpxchg_local which
has been copied from it) worked fine, but since we touch a pointer, the type
needs to be casted in the cmpxchg_local and cmpxchg macros.

The more recent code (586+) does not have this problem (the cast is already
there).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Christoph Lameter <clameter@xxxxxxx>
CC: Vegard Nossum <vegard.nossum@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: akpm@xxxxxxxxxxxxxxxxxxxx
---
 include/asm-x86/cmpxchg_32.h |   32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

Index: linux-2.6-lttng/include/asm-x86/cmpxchg_32.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86/cmpxchg_32.h	2008-02-10 06:26:50.000000000 -0500
+++ linux-2.6-lttng/include/asm-x86/cmpxchg_32.h	2008-02-10 06:41:43.000000000 -0500
@@ -269,22 +269,26 @@
 ({									\
 	__typeof__(*(ptr)) __ret;					\
 	if (likely(boot_cpu_data.x86 > 3))				\
-		__ret = __cmpxchg((ptr), (unsigned long)(o),		\
-					(unsigned long)(n), sizeof(*(ptr))); \
+		__ret = (__typeof__(*(ptr)))__cmpxchg((ptr),		\
+				(unsigned long)(o), (unsigned long)(n),	\
+				sizeof(*(ptr)));			\
 	else								\
-		__ret = cmpxchg_386((ptr), (unsigned long)(o),		\
-					(unsigned long)(n), sizeof(*(ptr))); \
+		__ret = (__typeof__(*(ptr)))cmpxchg_386((ptr),		\
+				(unsigned long)(o), (unsigned long)(n),	\
+				sizeof(*(ptr)));			\
 	__ret;								\
 })
 #define cmpxchg_local(ptr, o, n)					\
 ({									\
 	__typeof__(*(ptr)) __ret;					\
 	if (likely(boot_cpu_data.x86 > 3))				\
-		__ret = __cmpxchg_local((ptr), (unsigned long)(o),	\
-					(unsigned long)(n), sizeof(*(ptr))); \
+		__ret = (__typeof__(*(ptr)))__cmpxchg_local((ptr),	\
+				(unsigned long)(o), (unsigned long)(n),	\
+				sizeof(*(ptr)));			\
 	else								\
-		__ret = cmpxchg_386((ptr), (unsigned long)(o),		\
-					(unsigned long)(n), sizeof(*(ptr))); \
+		__ret = (__typeof__(*(ptr)))cmpxchg_386((ptr),		\
+				(unsigned long)(o), (unsigned long)(n),	\
+				sizeof(*(ptr)));			\
 	__ret;								\
 })
 #endif
@@ -301,10 +305,12 @@
 ({									\
 	__typeof__(*(ptr)) __ret;					\
 	if (likely(boot_cpu_data.x86 > 4))				\
-		__ret = __cmpxchg64((ptr), (unsigned long long)(o),	\
+		__ret = __typeof__(*(ptr))__cmpxchg64((ptr),		\
+				(unsigned long long)(o),		\
 				(unsigned long long)(n));		\
 	else								\
-		__ret = cmpxchg_486_u64((ptr), (unsigned long long)(o),	\
+		__ret = __typeof__(*(ptr))cmpxchg_486_u64((ptr),	\
+				(unsigned long long)(o),		\
 				(unsigned long long)(n));		\
 	__ret;								\
 })
@@ -312,10 +318,12 @@
 ({									\
 	__typeof__(*(ptr)) __ret;					\
 	if (likely(boot_cpu_data.x86 > 4))				\
-		__ret = __cmpxchg64_local((ptr), (unsigned long long)(o), \
+		__ret = __typeof__(*(ptr))__cmpxchg64_local((ptr),	\
+				(unsigned long long)(o),		\
 				(unsigned long long)(n));		\
 	else								\
-		__ret = cmpxchg_486_u64((ptr), (unsigned long long)(o),	\
+		__ret = __typeof__(*(ptr))cmpxchg_486_u64((ptr),	\
+				(unsigned long long)(o),		\
 				(unsigned long long)(n));		\
 	__ret;								\
 })
-- 
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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