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make atomic_read() behave consistently on s390

PATCH In review Chris Snook 2 participants 2 messages Aug 9, 2007

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Networking Network drivers Generic include/asm header files Atomic infrastructure
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Chris Snook

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PATCH 16/24 make atomic_read() behave consistently on s390

From: Chris Snook <[email protected]>

Make atomic[64]_read() volatile on s390, to ensure memory is actually read each time.

Signed-off-by Chris Snook <[email protected]>
include/asm-s390/atomic.h +6 -2
@@ -67,7 +67,11 @@ typedef struct {
 
 #endif /* __GNUC__ */
 
-#define atomic_read(v)          ((v)->counter)
+/*
+ * Casting to volatile here minimizes the need for barriers,
+ * without having to declare the type itself as volatile.
+ */
+#define atomic_read(v)          (*(volatile int *)&(v)->counter)
 #define atomic_set(v,i)         (((v)->counter) = (i))
 
 static __inline__ int atomic_add_return(int i, atomic_t * v)

@@ -182,7 +186,7 @@ typedef struct {
 
 #endif /* __GNUC__ */
 
-#define atomic64_read(v)          ((v)->counter)
+#define atomic64_read(v)          (*(volatile long long *)&(v)->counter)
 #define atomic64_set(v,i)         (((v)->counter) = (i))
 
 static __inline__ long long atomic64_add_return(long long i, atomic64_t * v)