Fix: sessiond: rotation thread: fatal error when not finding a session

The rotation thread implements scheduled rotations (by size) by
registering a trigger that monitors the session's consumed size and
notifies when the next rotation's size threshold is exceeded.

The notification is delivered asynchronously which doesn't prevent
the session from being destroyed before the rotation thread has
had the time to process the notification (and perform a rotation).

Since it is possible for a session to be destroyed by the time the
notification is processed, the rotation thread shouldn't handle
this eventuality as a fatal error (shutting down the thread).

Note that nobody reported this issue nor did I attempt to reproduce it.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I588054bad3542854851f28d34f2c758bdf420a34

diff --git a/src/bin/lttng-sessiond/rotation-thread.cpp b/src/bin/lttng-sessiond/rotation-thread.cpp
index 8754d48a1d2eeb519d2273cba67332c01bf50f31..ecc4c3ea730513a16845dc42dd1aacecc798fb27 100644 (file)
--- a/src/bin/lttng-sessiond/rotation-thread.cpp
+++ b/src/bin/lttng-sessiond/rotation-thread.cpp
@@ -25,6 +25,7 @@
 #include <lttng/notification/channel-internal.h>
 #include <lttng/rotate-internal.h>
 #include <lttng/location-internal.h>
+#include <lttng/condition/condition-internal.h>
 
 #include "rotation-thread.h"
 #include "lttng-sessiond.h"
@@ -659,10 +660,15 @@ int handle_condition(const struct lttng_condition *condition,
        session_lock_list();
        session = session_find_by_name(condition_session_name);
        if (!session) {
-               ret = -1;
-               session_unlock_list();
-               ERR("Session \"%s\" not found",
+               DBG("Failed to find session while handling notification: notification type = %s, session name = `%s`",
+                               lttng_condition_type_str(condition_type),
                                condition_session_name);
+               /*
+                * Not a fatal error: a session can be destroyed before we get
+                * the chance to handle the notification.
+                */
+               ret = 0;
+               session_unlock_list();
                goto end;
        }
        session_lock(session);