- if (!session) {
- ERR("Missing LTT session to get discarded events");
- goto end;
- }
- if (!session->ust_session) {
- ERR("Missing UST session to get discarded events");
+ if (!session || !session->ust_session) {
+ /*
+ * Not finding the session is not an error because there are
+ * multiple ways the channels can be torn down.
+ *
+ * 1) The session daemon can initiate the destruction of the
+ * ust app session after receiving a destroy command or
+ * during its shutdown/teardown.
+ * 2) The application, since we are in per-pid tracing, is
+ * unregistering and tearing down its ust app session.
+ *
+ * Both paths are protected by the session list lock which
+ * ensures that the accounting of lost packets and discarded
+ * events is done exactly once. The session is then unpublished
+ * from the session list, resulting in this condition.
+ */