[patch 48/71] parisc: fix ldcw inline assembler

[Greg KH]

2.6.30-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Helge Deller <deller@xxxxxx>

commit 7d17e2763129ea307702fcdc91f6e9d114b65c2d upstream.

There are two reasons to expose the memory *a in the asm:

1) To prevent the compiler from discarding a preceeding write to *a, and
2) to prevent it from caching *a in a register over the asm.

The change has had a few days testing with a SMP build of 2.6.22.19
running on a rp3440.

This patch is about the correctness of the __ldcw() macro itself.
The use of the macro should be confined to small inline functions
to try to limit the effect of clobbering memory on GCC's optimization
of loads and stores.

Signed-off-by: Dave Anglin <dave.anglin@xxxxxxxxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Kyle McMartin <kyle@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/parisc/include/asm/system.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/parisc/include/asm/system.h
+++ b/arch/parisc/include/asm/system.h
@@ -168,8 +168,8 @@ static inline void set_eiem(unsigned lon
 /* LDCW, the only atomic read-write operation PA-RISC has. *sigh*.  */
 #define __ldcw(a) ({						\
 	unsigned __ret;						\
-	__asm__ __volatile__(__LDCW " 0(%1),%0"			\
-		: "=r" (__ret) : "r" (a));			\
+	__asm__ __volatile__(__LDCW " 0(%2),%0"			\
+		: "=r" (__ret), "+m" (*(a)) : "r" (a));		\
 	__ret;							\
 })
 


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