X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;f=include%2Flinux%2Fcompiler.h;h=c8bd2daf95ec51e0f42ad05e6b8c13be1300ce16;hb=e9f76354ce83a20c7768ad37caa033f6506b4f96;hp=dcae0c8d97e6e2d04a8db04494e899eb403e1c18;hpb=03414e57ad9875d0c8bfa5a4a65813cb2157372e;p=linux-2.6-omap-h63xx.git

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index dcae0c8d97e..c8bd2daf95e 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -182,4 +182,16 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 # define __section(S) __attribute__ ((__section__(#S)))
 #endif
 
+/*
+ * Prevent the compiler from merging or refetching accesses.  The compiler
+ * is also forbidden from reordering successive instances of ACCESS_ONCE(),
+ * but only when the compiler is aware of some particular ordering.  One way
+ * to make the compiler aware of ordering is to put the two invocations of
+ * ACCESS_ONCE() in different C statements.
+ *
+ * This macro does absolutely -nothing- to prevent the CPU from reordering,
+ * merging, or refetching absolutely anything at any time.
+ */
+#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
+
 #endif /* __LINUX_COMPILER_H */