3 files changed, 19 insertions, 4 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 6c81f9c..aa08be6 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1050,12 +1050,13 @@ static void trace_module_remove_events(struct module *mod)
 	struct ftrace_event_call *call, *p;
 	bool found = false;
 
+	down_write(&trace_event_mutex);
 	list_for_each_entry_safe(call, p, &ftrace_events, list) {
 		if (call->mod == mod) {
 			found = true;
 			ftrace_event_enable_disable(call, 0);
 			if (call->event)
-				unregister_ftrace_event(call->event);
+				__unregister_ftrace_event(call->event);
 			debugfs_remove_recursive(call->dir);
 			list_del(&call->list);
 			trace_destroy_fields(call);
@@ -1079,6 +1080,7 @@ static void trace_module_remove_events(struct module *mod)
 	 */
 	if (found)
 		tracing_reset_current_online_cpus();
+	up_write(&trace_event_mutex);
 }
 
 static int trace_module_notify(struct notifier_block *self,
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index c05aff4..7938f3a 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -14,7 +14,7 @@
 /* must be a power of 2 */
 #define EVENT_HASHSIZE	128
 
-static DECLARE_RWSEM(trace_event_mutex);
+DECLARE_RWSEM(trace_event_mutex);
 
 DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
 EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
@@ -702,6 +702,16 @@ int register_ftrace_event(struct trace_event *event)
 }
 EXPORT_SYMBOL_GPL(register_ftrace_event);
 
+/*
+ * Used by module code with the trace_event_mutex held for write.
+ */
+int __unregister_ftrace_event(struct trace_event *event)
+{
+	hlist_del(&event->node);
+	list_del(&event->list);
+	return 0;
+}
+
 /**
  * unregister_ftrace_event - remove a no longer used event
  * @event: the event to remove
@@ -709,8 +719,7 @@ EXPORT_SYMBOL_GPL(register_ftrace_event);
 int unregister_ftrace_event(struct trace_event *event)
 {
 	down_write(&trace_event_mutex);
-	hlist_del(&event->node);
-	list_del(&event->list);
+	__unregister_ftrace_event(event);
 	up_write(&trace_event_mutex);
 
 	return 0;
diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h
index ac240e7..d38bec4 100644
--- a/kernel/trace/trace_output.h
+++ b/kernel/trace/trace_output.h
@@ -27,6 +27,10 @@ extern struct trace_event *ftrace_find_event(int type);
 extern enum print_line_t trace_nop_print(struct trace_iterator *iter,
 					 int flags);
 
+/* used by module unregistering */
+extern int __unregister_ftrace_event(struct trace_event *event);
+extern struct rw_semaphore trace_event_mutex;
+
 #define MAX_MEMHEX_BYTES	8
 #define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)