make atomic_read() behave consistently on sparc

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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2007-08-09 14:15 UTC #0 lore raw

PATCH 20/24 make atomic_read() behave consistently on sparc

From: Chris Snook <[email protected]>

Purify volatile use for atomic_t on sparc.
Leave atomic24_t alone, since it's only used by sparc-specific code.

Signed-off-by Chris Snook <[email protected]>

include/asm-sparc/atomic.h +6 -2

@@ -13,7 +13,7 @@
 
 #include <linux/types.h>
 
-typedef struct { volatile int counter; } atomic_t;
+typedef struct { int counter; } atomic_t;
 
 #ifdef __KERNEL__

@@ -61,7 +61,11 @@ extern int atomic_cmpxchg(atomic_t *, in
 extern int atomic_add_unless(atomic_t *, int, int);
 extern void atomic_set(atomic_t *, int);
 
-#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_add(i, v)	((void)__atomic_add_return( (int)(i), (v)))
 #define atomic_sub(i, v)	((void)__atomic_add_return(-(int)(i), (v)))