[patch 3/4] Markers - Remove ACCESS_ONCE

[Mathieu Desnoyers]

As Paul pointed out, the ACCESS_ONCE are not needed because we already have the
explicit surrounding memory barriers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Christoph Hellwig <hch@xxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxx>
CC: Mike Mason <mmlnx@xxxxxxxxxx>
CC: Dipankar Sarma <dipankar@xxxxxxxxxx>
CC: David Smith <dsmith@xxxxxxxxxx>
CC: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: Adrian Bunk <adrian.bunk@xxxxxxxxx>
---
 kernel/marker.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Index: linux-2.6-lttng/kernel/marker.c
===================================================================
--- linux-2.6-lttng.orig/kernel/marker.c	2008-03-19 18:30:26.000000000 -0400
+++ linux-2.6-lttng/kernel/marker.c	2008-03-19 18:32:16.000000000 -0400
@@ -109,13 +109,13 @@ void marker_probe_cb(const struct marker
 	 * modules and they insure RCU read coherency.
 	 */
 	preempt_disable();
-	ptype = ACCESS_ONCE(mdata->ptype);
+	ptype = mdata->ptype;
 	if (likely(!ptype)) {
 		marker_probe_func *func;
 		/* Must read the ptype before ptr. They are not data dependant,
 		 * so we put an explicit smp_rmb() here. */
 		smp_rmb();
-		func = ACCESS_ONCE(mdata->single.func);
+		func = mdata->single.func;
 		/* Must read the ptr before private data. They are not data
 		 * dependant, so we put an explicit smp_rmb() here. */
 		smp_rmb();
@@ -133,7 +133,7 @@ void marker_probe_cb(const struct marker
 		 * in the fast path, so put the explicit barrier here.
 		 */
 		smp_read_barrier_depends();
-		multi = ACCESS_ONCE(mdata->multi);
+		multi = mdata->multi;
 		for (i = 0; multi[i].func; i++) {
 			va_start(args, fmt);
 			multi[i].func(multi[i].probe_private, call_private, fmt,
@@ -161,13 +161,13 @@ void marker_probe_cb_noarg(const struct 
 	char ptype;
 
 	preempt_disable();
-	ptype = ACCESS_ONCE(mdata->ptype);
+	ptype = mdata->ptype;
 	if (likely(!ptype)) {
 		marker_probe_func *func;
 		/* Must read the ptype before ptr. They are not data dependant,
 		 * so we put an explicit smp_rmb() here. */
 		smp_rmb();
-		func = ACCESS_ONCE(mdata->single.func);
+		func = mdata->single.func;
 		/* Must read the ptr before private data. They are not data
 		 * dependant, so we put an explicit smp_rmb() here. */
 		smp_rmb();
@@ -183,7 +183,7 @@ void marker_probe_cb_noarg(const struct 
 		 * in the fast path, so put the explicit barrier here.
 		 */
 		smp_read_barrier_depends();
-		multi = ACCESS_ONCE(mdata->multi);
+		multi = mdata->multi;
 		for (i = 0; multi[i].func; i++)
 			multi[i].func(multi[i].probe_private, call_private, fmt,
 				&args);

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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