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| author | Lachlan McIlroy <lachlan@redback.melbourne.sgi.com> | 2008-05-19 15:09:05 +1000 |
|---|---|---|
| committer | Lachlan McIlroy <lachlan@redback.melbourne.sgi.com> | 2008-05-19 15:09:05 +1000 |
| commit | c203e45f069af47ca7623e4dcd8c00bfba2722e4 (patch) | |
| tree | 4563115b6565dcfd97015c1c9366fb3d07cabf19 /include/linux/compiler.h | |
| parent | a94477da38e0b261a7ecea71f4c95a3bcd5be69c (diff) | |
| parent | b8291ad07a7f3b5b990900f0001198ac23ba893e (diff) | |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-linus
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 */ |