linux-kernel - [PATCH tip/cor/rcu] remove redundant ACCESS

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Message-ID: <20080817195036.GA27585@linux.vnet.ibm.com>
Date:	Sun, 17 Aug 2008 12:50:36 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, akpm@...ux-foundation.org, dipankar@...ibm.com,
	josht@...ux.vnet.ibm.com, rostedt@...dmis.org, dvhltc@...ibm.com,
	niv@...ibm.com
Subject: [PATCH tip/cor/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@...ux.vnet.ibm.com>
---

 include/linux/compiler.h |    4 +++-
 kernel/rcupreempt.c      |    8 --------
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index c8bd2da..8322141 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))
 
diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 2782793..ca4bbbe 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -59,14 +59,6 @@
 #include <linux/rcupreempt_trace.h>
 
 /*
- * Macro that prevents the compiler from reordering accesses, but does
- * absolutely -nothing- to prevent CPUs from reordering.  This is used
- * only to mediate communication between mainline code and hardware
- * interrupt and NMI handlers.
- */
-#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
-
-/*
  * PREEMPT_RCU data structures.
  */
 
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