perf_events: Fix read() bogus counts when in error state
[linux-2.6.git] / kernel / perf_event.c
index f8c7939..0b9ca2d 100644 (file)
@@ -338,7 +338,16 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
                event->group_leader->nr_siblings--;
 
        update_event_times(event);
-       event->state = PERF_EVENT_STATE_OFF;
+
+       /*
+        * If event was in error state, then keep it
+        * that way, otherwise bogus counts will be
+        * returned on read(). The only way to get out
+        * of error state is by explicit re-enabling
+        * of the event
+        */
+       if (event->state > PERF_EVENT_STATE_OFF)
+               event->state = PERF_EVENT_STATE_OFF;
 
        /*
         * If this was a group event with sibling events then