* [PATCH 7/24] make atomic_read() behave consistently on h8300
@ 2007-08-09 13:44 Chris Snook
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From: Chris Snook @ 2007-08-09 13:44 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_read() volatile on h8300. This ensures that busy-waiting
for an interrupt handler to change an atomic_t won't get compiled to an
infinite loop, consistent with SMP architectures.
Signed-off-by: Chris Snook <csnook@redhat.com>
--- linux-2.6.23-rc2-orig/include/asm-h8300/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-h8300/atomic.h 2007-08-09 06:45:43.000000000 -0400
@@ -9,7 +9,11 @@
typedef struct { int counter; } atomic_t;
#define ATOMIC_INIT(i) { (i) }
-#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)
#include <asm/system.h>
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