linux-kernel - [PATCH UPDATED 1/2] trace_events_filter: use rcu_assign_pointer() when setting ftrace_event

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Message-ID: <20111123164949.GA29639@google.com>
Date:	Wed, 23 Nov 2011 08:49:49 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH UPDATED 1/2] trace_events_filter: use rcu_assign_pointer()
 when setting ftrace_event_call->filter

ftrace_event_call->filter is sched RCU protected but didn't use
rcu_assign_pointer().  Use it.

TODO: Add proper __rcu annotation to call->filter and all its users.

-v2: Use RCU_INIT_POINTER() for %NULL clearing as suggested by Eric.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Eric Dumazet <eric.dumazet@...il.com>
---
 kernel/trace/trace_events_filter.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: work/kernel/trace/trace_events_filter.c
===================================================================
--- work.orig/kernel/trace/trace_events_filter.c
+++ work/kernel/trace/trace_events_filter.c
@@ -1686,7 +1686,7 @@ static int replace_system_preds(struct e
 		 * replace the filter for the call.
 		 */
 		filter = call->filter;
-		call->filter = filter_item->filter;
+		rcu_assign_pointer(call->filter, filter_item->filter);
 		filter_item->filter = filter;
 
 		fail = false;
@@ -1741,7 +1741,7 @@ int apply_event_filter(struct ftrace_eve
 		filter = call->filter;
 		if (!filter)
 			goto out_unlock;
-		call->filter = NULL;
+		RCU_INIT_POINTER(call->filter, NULL);
 		/* Make sure the filter is not being used */
 		synchronize_sched();
 		__free_filter(filter);
@@ -1782,7 +1782,7 @@ out:
 	 * string
 	 */
 	tmp = call->filter;
-	call->filter = filter;
+	rcu_assign_pointer(call->filter, filter);
 	if (tmp) {
 		/* Make sure the call is done with the filter */
 		synchronize_sched();
--
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