rcu: remove redundant ACCESS_ONCE definition from rcupreempt.c

Remove the redundant definition of ACCESS_ONCE() from rcupreempt.c in
favor of the one in compiler.h.  Also merge the comment header from
rcupreempt.c's definition into that in compiler.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index c8bd2daf95ec..8322141ee480 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -190,7 +190,9 @@ extern void __chk_io_ptr(const volatile void __iomem *);
  * 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.
+ * merging, or refetching absolutely anything at any time.  Its main intended
+ * use is to mediate communication between process-level code and irq/NMI
+ * handlers, all running on the same CPU.
  */
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))