[Bug 732226] New: Races when sessions time out

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=732226
  GStreamer | gst-rtsp-server | git

           Summary: Races when sessions time out
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-rtsp-server
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: ognyan.tonchev at axis.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


I am having trouble because of a race in gst-rtsp-server when expired sessions
are being removed. In my case the GSource responsible for cleaning up the
timed-out sessions is attached to the application default context. The GSource
is set up the following way:

source = gst_rtsp_session_pool_create_watch ()
g_source_set_callback (source, (GSourceFunc) session_timeout_cb, NULL, NULL);

And the GSource callback looks like this:

session_timeout_cb(pool) {
  gst_rtsp_session_pool_filter (pool, remove_expired_session, NULL);
}

remove_expired_session() {
  if (gst_rtsp_session_is_expired (session)) {
    return GST_RTSP_FILTER_REMOVE;
  }
  return GST_RTSP_FILTER_KEEP;
}

And this code introduces a race in rtsp-client.c. The race is between the week
reference callback client_session_finalized () run in the main context and the
rest of the functions in RTSPClient manipulating the internal sessions list
(the code does not even keep hard references to the sessions) from clients own
context.

The result I am getting is segmentation faults of different kind when the
server is under high load and sessions start to expire.

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