Fix: rotation: hang on destroy when using scheduled rotation based on timer

Observed issue
==============

The following scenario results in a hang for `lttng destroy`:

lttng create test
lttng enable-event -u -a
lttng enable-rotation --timer 100000
lttng start
lttng stop
lttng start
lttng destroy

Cause
=====

There is an imbalance in how many times we start the rotation timer.

The rotation timer is only removed on `lttng destroy` or when disabling
a time-based-rotation. On the other hand, the timer is "started"
on `lttng start` and when enabling a time based rotation.

The imbalance emerging from a start/stop/start sequence would prevent the
teardown of the session object since each time the timer is started a
reference to the session is held.

Solution
========

Do not start the rotation schedule timer if it was already launched.

Known drawbacks
=========

None.

Change-Id: Ic5b8938166358fe7629187bebdf02a09e90846c0
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-sessiond/cmd.cpp b/src/bin/lttng-sessiond/cmd.cpp
index 0ca7f217244bd81d7cba98431347d60e7f61c9b4..0e9821eb693f327fa7b69c74f104df1b0398bfea 100644 (file)
--- a/src/bin/lttng-sessiond/cmd.cpp
+++ b/src/bin/lttng-sessiond/cmd.cpp
@@ -2818,7 +2818,7 @@ int cmd_start_trace(struct ltt_session *session)
         */
        session->rotated_after_last_stop = false;
 
-       if (session->rotate_timer_period) {
+       if (session->rotate_timer_period && !session->rotation_schedule_timer_enabled) {
                int int_ret = timer_session_rotation_schedule_timer_start(
                                session, session->rotate_timer_period);