[PATCH 12/24] make atomic_read() behave consistently on m68k
From: Chris Snook <hidden>
Date: 2007-08-09 13:59:23
Also in:
linux-arch, lkml
From: Chris Snook <redacted> Make atomic_read() volatile on m68k. 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 <redacted>
--- linux-2.6.23-rc2-orig/include/asm-m68k/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-m68k/atomic.h 2007-08-09 06:58:24.000000000 -0400@@ -16,7 +16,11 @@ 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) static inline void atomic_add(int i, atomic_t *v)