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

STALE6948d

2 messages, 2 authors, 2007-08-09 · open the first message on its own page

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

From: Chris Snook <hidden>
Date: 2007-08-09 14:07:41 

From: Chris Snook <redacted>

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

Signed-off-by: Chris Snook <redacted>

--- linux-2.6.23-rc2-orig/include/asm-s390/atomic.h	2007-08-08 17:48:53.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-s390/atomic.h	2007-08-09 07:18:56.000000000 -0400
@@ -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)

Re: [PATCH 16/24] make atomic_read() behave consistently on s390

From: Martin Schwidefsky <hidden>
Date: 2007-08-09 14:33:58 

On Thu, 2007-08-09 at 10:06 -0400, Chris Snook wrote:
From: Chris Snook <redacted>

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

Signed-off-by: Chris Snook <redacted>
Acked-by: Martin Schwidefsky <redacted>

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.
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