[PATCH 6/24] make atomic_read() behave consistently on frv

Chris Snook
2007-08-09T13:43:18Z

From: Chris Snook <csnook@redhat.com>

Make atomic_read() volatile on frv. 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-frv/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-frv/atomic.h 2007-08-09 06:41:48.000000000 -0400
@@ -40,7 +40,12 @@ 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))

#ifndef CONFIG_FRV_OUTOFLINE_ATOMIC_OPS