diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-10 19:51:16 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-10 19:51:16 -0700 |
commit | 9c3cdc1f83a6e07092392ff4aba6466517dbd1d0 (patch) | |
tree | 4dc890f607da4f85ca3a66770e4bce109879e69b /include/linux/compiler.h | |
parent | 3ed43c745d2ce0c4ca15ad406285d1cc7e8ceec3 (diff) | |
download | linux-stable-9c3cdc1f83a6e07092392ff4aba6466517dbd1d0.tar.gz linux-stable-9c3cdc1f83a6e07092392ff4aba6466517dbd1d0.tar.bz2 linux-stable-9c3cdc1f83a6e07092392ff4aba6466517dbd1d0.zip |
Move ACCESS_ONCE() to <linux/compiler.h>
It actually makes much more sense there, and we do tend to need it for
non-RCU usage too. Moving it to <linux/compiler.h> will allow some
other cases that have open-coded the same logic to use the same helper
function that RCU has used.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r-- | include/linux/compiler.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index dcae0c8d97e6..c8bd2daf95ec 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 */ |