[PATCH] tracing: Add rcu annotation around file->filter accesses

[Steven Rostedt]

From: Steven Rostedt <rost...@goodmis.org>

Running sparse on trace_events_filter.c triggered several warnings about
file->filter being accessed directly even though it's annotated with __rcu.

Add rcu_dereference() around it and shuffle the logic slightly so that
it's always referenced via accessor functions.

Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c 
b/kernel/trace/trace_events_filter.c
index 711520081741..ea8b364b6818 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1250,7 +1250,9 @@ static void append_filter_err(struct trace_array *tr,
 
 static inline struct event_filter *event_filter(struct trace_event_file *file)
 {
-       return file->filter;
+       return rcu_dereference_protected(file->filter,
+                                        lockdep_is_held(&event_mutex));
+
 }
 
 /* caller must hold event_mutex */
@@ -1320,7 +1322,7 @@ void free_event_filter(struct event_filter *filter)
 static inline void __remove_filter(struct trace_event_file *file)
 {
        filter_disable(file);
-       remove_filter_string(file->filter);
+       remove_filter_string(event_filter(file));
 }
 
 static void filter_free_subsystem_preds(struct trace_subsystem_dir *dir,
@@ -1405,7 +1407,7 @@ static void try_delay_free_filter(struct event_filter 
*filter)
 
 static inline void __free_subsystem_filter(struct trace_event_file *file)
 {
-       __free_filter(file->filter);
+       __free_filter(event_filter(file));
        file->filter = NULL;
 }
 
@@ -1465,7 +1467,7 @@ static void filter_free_subsystem_filters(struct 
trace_subsystem_dir *dir,
        list_for_each_entry(file, &tr->events, list) {
                if (file->system != dir || !file->filter)
                        continue;
-               __free_filter(file->filter);
+               __free_subsystem_filter(file);
        }
        __free_filter(filter);
 }
-- 
2.47.2