tracing/filters: add filter_mutex to protect filter predicates

This patch adds a filter_mutex to prevent the filter predicates from
being accessed concurrently by various external functions.

It's based on a previous patch by Li Zefan:
        "[PATCH 7/7] tracing/filters: make filter preds RCU safe"

v2 changes:

- fixed wrong value returned in a add_subsystem_pred() failure case
  noticed by Li Zefan.

[ Impact: fix trace filter corruption/crashes on parallel access ]

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: paulmck@linux.vnet.ibm.com
LKML-Reference: <1239946028.6639.13.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8817c18..247948e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -757,13 +757,15 @@ struct filter_pred {
 };
 
 extern void filter_free_pred(struct filter_pred *pred);
-extern void filter_print_preds(struct filter_pred **preds, int n_preds,
+extern void filter_print_preds(struct ftrace_event_call *call,
 			       struct trace_seq *s);
 extern int filter_parse(char **pbuf, struct filter_pred *pred);
 extern int filter_add_pred(struct ftrace_event_call *call,
 			   struct filter_pred *pred);
 extern void filter_disable_preds(struct ftrace_event_call *call);
 extern void filter_free_subsystem_preds(struct event_subsystem *system);
+extern void filter_print_subsystem_preds(struct event_subsystem *system,
+					 struct trace_seq *s);
 extern int filter_add_subsystem_pred(struct event_subsystem *system,
 				     struct filter_pred *pred);