[PATCH] arm: xen: correct barriers in xchg_xen_ulong

[Ian Campbell]

We can use an smp_wmb rather than a wmb here and we also need one after the
exchange. Spotted by Rob Herring.

Signed-off-by: Ian Campbell <ijc@xxxxxxxxxxxxxx>
---
 arch/arm/include/asm/xen/events.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/xen/events.h b/arch/arm/include/asm/xen/events.h
index 5c27696..0e1f59e 100644
--- a/arch/arm/include/asm/xen/events.h
+++ b/arch/arm/include/asm/xen/events.h
@@ -25,7 +25,7 @@ static inline xen_ulong_t xchg_xen_ulong(xen_ulong_t *ptr, xen_ulong_t val)
 	xen_ulong_t oldval;
 	unsigned int tmp;
 
-	wmb();
+	smp_wmb();
 	asm volatile("@ xchg_xen_ulong\n"
 		"1:     ldrexd  %0, %H0, [%3]\n"
 		"       strexd  %1, %2, %H2, [%3]\n"
@@ -34,6 +34,7 @@ static inline xen_ulong_t xchg_xen_ulong(xen_ulong_t *ptr, xen_ulong_t val)
 		: "=&r" (oldval), "=&r" (tmp)
 		: "r" (val), "r" (ptr)
 		: "memory", "cc");
+	smp_wmb();
 	return oldval;
 }
 
-- 
1.7.10.4



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/