tracing: Add rcu annotation around file->filter accesses

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.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250607102821.6c7effbf@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 7115200817410b1ba177cbf8e89ab8ffd60d1d34..ea8b364b6818fae7e4fbc78ebfea948fa7e8cec1 100644 (file)
--- 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);
 }