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Commit 9c3cdc1f83a6e07092392ff4aba6466517dbd1d0

Authored by Linus Torvalds
1 parent 3ed43c745d
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 2 changed files with 12 additions and 12 deletions Side-by-side Diff

include/linux/compiler.h
Diff comments   View file @ 9c3cdc1
... ... @@ -182,5 +182,17 @@
182 182 # define __section(S) __attribute__ ((__section__(#S)))
183 183 #endif
184 184  
  185 +/*
  186 + * Prevent the compiler from merging or refetching accesses. The compiler
  187 + * is also forbidden from reordering successive instances of ACCESS_ONCE(),
  188 + * but only when the compiler is aware of some particular ordering. One way
  189 + * to make the compiler aware of ordering is to put the two invocations of
  190 + * ACCESS_ONCE() in different C statements.
  191 + *
  192 + * This macro does absolutely -nothing- to prevent the CPU from reordering,
  193 + * merging, or refetching absolutely anything at any time.
  194 + */
  195 +#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
  196 +
185 197 #endif /* __LINUX_COMPILER_H */
include/linux/rcupdate.h
Diff comments   View file @ 9c3cdc1
... ... @@ -131,18 +131,6 @@
131 131 */
132 132 #define rcu_read_unlock_bh() __rcu_read_unlock_bh()
133 133  
134   -/*
135   - * Prevent the compiler from merging or refetching accesses. The compiler
136   - * is also forbidden from reordering successive instances of ACCESS_ONCE(),
137   - * but only when the compiler is aware of some particular ordering. One way
138   - * to make the compiler aware of ordering is to put the two invocations of
139   - * ACCESS_ONCE() in different C statements.
140   - *
141   - * This macro does absolutely -nothing- to prevent the CPU from reordering,
142   - * merging, or refetching absolutely anything at any time.
143   - */
144   -#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
145   -
146 134 /**
147 135 * rcu_dereference - fetch an RCU-protected pointer in an
148 136 * RCU read-side critical section. This pointer may later