* [PATCH 16/24] make atomic_read() behave consistently on s390
@ 2007-08-09 14:06 Chris Snook
2007-08-09 14:36 ` Martin Schwidefsky
0 siblings, 1 reply; 2+ messages in thread
From: Chris Snook @ 2007-08-09 14:06 UTC (permalink / raw)
To: linux-kernel, linux-arch, torvalds
Cc: netdev, akpm, ak, heiko.carstens, davem, schwidefsky, wensong,
horms, wjiang, cfriesen, zlynx, rpjday, jesper.juhl
From: Chris Snook <csnook@redhat.com>
Make atomic[64]_read() volatile on s390, to ensure memory is actually read
each time.
Signed-off-by: Chris Snook <csnook@redhat.com>
--- 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)
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH 16/24] make atomic_read() behave consistently on s390
2007-08-09 14:06 [PATCH 16/24] make atomic_read() behave consistently on s390 Chris Snook
@ 2007-08-09 14:36 ` Martin Schwidefsky
0 siblings, 0 replies; 2+ messages in thread
From: Martin Schwidefsky @ 2007-08-09 14:36 UTC (permalink / raw)
To: Chris Snook
Cc: linux-kernel, linux-arch, torvalds, netdev, akpm, ak,
heiko.carstens, davem, wensong, horms, wjiang, cfriesen, zlynx,
rpjday, jesper.juhl
On Thu, 2007-08-09 at 10:06 -0400, Chris Snook wrote:
> From: Chris Snook <csnook@redhat.com>
>
> Make atomic[64]_read() volatile on s390, to ensure memory is actually read
> each time.
>
> Signed-off-by: Chris Snook <csnook@redhat.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
^ permalink raw reply [flat|nested] 2+ messages in thread
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