tracing: Fix rcu handling of event_trigger_data filter field

The filter field of the event_trigger_data structure is protected under
RCU sched locks. It was not annotated as such, and after doing so,
sparse pointed out several locations that required fix ups.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Tested-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 0380cab..02b592f 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1057,7 +1057,7 @@ struct event_trigger_data {
        int                             ref;
        struct event_trigger_ops        *ops;
        struct event_command            *cmd_ops;
-       struct event_filter             *filter;
+       struct event_filter __rcu       *filter;
        char                            *filter_str;
        void                            *private_data;
        struct list_head                list;

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 12ac8a5..f6dd115 100644 (file)
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -67,6 +67,7 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
 {
        struct event_trigger_data *data;
        enum event_trigger_type tt = ETT_NONE;
+       struct event_filter *filter;
 
        if (list_empty(&file->triggers))
                return tt;
@@ -76,7 +77,8 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
                        data->ops->func(data);
                        continue;
                }
-               if (data->filter && !filter_match_preds(data->filter, rec))
+               filter = rcu_dereference(data->filter);
+               if (filter && !filter_match_preds(filter, rec))
                        continue;
                if (data->cmd_ops->post_trigger) {
                        tt |= data->cmd_ops->trigger_type;
@@ -703,7 +705,7 @@ static int set_trigger_filter(char *filter_str,
        if (ret)
                goto out;
  assign:
-       tmp = data->filter;
+       tmp = rcu_access_pointer(data->filter);
 
        rcu_assign_pointer(data->filter, filter);
 
@@ -719,7 +721,7 @@ static int set_trigger_filter(char *filter_str,
        if (filter_str) {
                data->filter_str = kstrdup(filter_str, GFP_KERNEL);
                if (!data->filter_str) {
-                       free_event_filter(data->filter);
+                       free_event_filter(rcu_access_pointer(data->filter));
                        data->filter = NULL;
                        ret = -ENOMEM;
                }