tracing: add trace_event_read_lock()

[pandora-kernel.git] / kernel / trace / trace_output.c

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 489c0e8..7136420 100644 (file)
--- 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 DEFINE_MUTEX(trace_event_mutex);
+static DECLARE_RWSEM(trace_event_mutex);
 static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
 
 static int next_event_type = __TRACE_LAST_TYPE + 1;
@@ -466,6 +466,7 @@ static int task_state_char(unsigned long state)
  * @type: the type of event to look for
  *
  * Returns an event of type @type otherwise NULL
+ * Called with trace_event_read_lock() held.
  */
 struct trace_event *ftrace_find_event(int type)
 {
@@ -475,7 +476,7 @@ struct trace_event *ftrace_find_event(int type)
 
        key = type & (EVENT_HASHSIZE - 1);
 
-       hlist_for_each_entry_rcu(event, n, &event_hash[key], node) {
+       hlist_for_each_entry(event, n, &event_hash[key], node) {
                if (event->type == type)
                        return event;
        }
@@ -513,6 +514,16 @@ static int trace_search_list(struct list_head **list)
        return last + 1;
 }
 
+void trace_event_read_lock(void)
+{
+       down_read(&trace_event_mutex);
+}
+
+void trace_event_read_unlock(void)
+{
+       up_read(&trace_event_mutex);
+}
+
 /**
  * register_ftrace_event - register output for an event type
  * @event: the event type to register
@@ -533,7 +544,7 @@ int register_ftrace_event(struct trace_event *event)
        unsigned key;
        int ret = 0;
 
-       mutex_lock(&trace_event_mutex);
+       down_write(&trace_event_mutex);
 
        if (WARN_ON(!event))
                goto out;
@@ -581,11 +592,11 @@ int register_ftrace_event(struct trace_event *event)
 
        key = event->type & (EVENT_HASHSIZE - 1);
 
-       hlist_add_head_rcu(&event->node, &event_hash[key]);
+       hlist_add_head(&event->node, &event_hash[key]);
 
        ret = event->type;
  out:
-       mutex_unlock(&trace_event_mutex);
+       up_write(&trace_event_mutex);
 
        return ret;
 }
@@ -597,10 +608,10 @@ EXPORT_SYMBOL_GPL(register_ftrace_event);
  */
 int unregister_ftrace_event(struct trace_event *event)
 {
-       mutex_lock(&trace_event_mutex);
+       down_write(&trace_event_mutex);
        hlist_del(&event->node);
        list_del(&event->list);
-       mutex_unlock(&trace_event_mutex);
+       up_write(&trace_event_mutex);
 
        return 0;
 }