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make atomic_read() behave consistently on blackfin

PATCH In review Chris Snook 1 participant 1 message 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 4/24 make atomic_read() behave consistently on blackfin

From: Chris Snook <[email protected]>

Make atomic_read() volatile on blackfin. 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 <[email protected]>
include/asm-blackfin/atomic.h +5 -1
@@ -18,7 +18,11 @@ typedef struct {
 } 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)
 
 static __inline__ void atomic_add(int i, atomic_t * v)