tracing/profile: fix profile_disable vs module_unload

If the correspoding module is unloaded before ftrace_profile_disable()
is called, event->profile_disable() won't be called, which can
cause oops:

  # insmod trace-events-sample.ko
  # perf record -f -a -e sample:foo_bar sleep 3 &
  # sleep 1
  # rmmod trace_events_sample
  # insmod trace-events-sample.ko
  OOPS!
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A9214E3.2070807@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_event_profile.c

@@ -5,6 +5,7 @@
  *
  */
 
+#include <linux/module.h>
 #include "trace.h"
 
 int ftrace_profile_enable(int event_id)
@@ -14,7 +15,8 @@ int ftrace_profile_enable(int event_id)
 
 	mutex_lock(&event_mutex);
 	list_for_each_entry(event, &ftrace_events, list) {
-		if (event->id == event_id && event->profile_enable) {
+		if (event->id == event_id && event->profile_enable &&
+		    try_module_get(event->mod)) {
 			ret = event->profile_enable(event);
 			break;
 		}
@@ -32,6 +34,7 @@ void ftrace_profile_disable(int event_id)
 	list_for_each_entry(event, &ftrace_events, list) {
 		if (event->id == event_id) {
 			event->profile_disable(event);
+			module_put(event->mod);
 			break;
 		}
 	}