BUG/MEDIUM: lua/notification: memory leak

The thread patches adds refcount for notifications. The notifications are
used with the Lua cosocket. These refcount free the notifications when
the session is cleared. In the Lua task case, it not have sessions, so
the nofications are never cleraed.

This patch adds a garbage collector for signals. The garbage collector
just clean the notifications for which the end point is disconnected.

This patch should be backported in 1.8

include/proto/task.h

@@ -326,6 +326,26 @@ static inline void notification_purge(struct list *purge)
 	}
 }
 
+/* In some cases, the disconnected notifications must be cleared.
+ * This function just release memory blocs. The purge list is not
+ * locked because it is owned by only one process. Before browsing
+ * this list, the caller must ensure to be the only one browser.
+ * The "com" is not locked because when com->task is NULL, the
+ * notification is no longer used.
+ */
+static inline void notification_gc(struct list *purge)
+{
+	struct notification *com, *back;
+
+	/* Delete all pending communication signals. */
+	list_for_each_entry_safe (com, back, purge, purge_me) {
+		if (com->task)
+			continue;
+		LIST_DEL(&com->purge_me);
+		pool_free(pool_head_notification, com);
+	}
+}
+
 /* This function sends signals. It wakes all the tasks attached
  * to a list head, and remove the signal, and free the used
  * memory. The wake list is not locked because it is owned by

src/hlua.c

@@ -5510,6 +5510,7 @@ static struct task *hlua_process_task(struct task *task)
 		break;
 
 	case HLUA_E_AGAIN: /* co process or timeout wake me later. */
+		notification_gc(&hlua->com);
 		if (hlua->wake_time != TICK_ETERNITY)
 			task->expire = hlua->wake_time;
 		break;