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Commit 9c3cdc1f authored by Linus Torvalds's avatar Linus Torvalds
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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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3ed43c74

include/linux/compiler.h

+12 −0
Original line number Diff line number Diff line
@@ -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 */

include/linux/rcupdate.h

+0 −12
Original line number Diff line number Diff line
@@ -131,18 +131,6 @@ struct rcu_head { 
 */

#define rcu_read_unlock_bh() __rcu_read_unlock_bh()



/*

 * 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))



/**

 * rcu_dereference - fetch an RCU-protected pointer in an

 * RCU read-side critical section.  This pointer may later