[Bug 755232] New: dashdemux: demux->cancelled is not properly protected

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=755232

            Bug ID: 755232
           Summary: dashdemux: demux->cancelled is not properly protected
    Classification: Platform
           Product: GStreamer
           Version: git master
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: florin.apostol at oregan.net
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

When a variable is shared between 2 threads, both read and write operations on
the variable must be performed with the same lock taken.

I've done an analysis on how demux->cancelled variable is locked before access:

write access, variable set to FALSE
gst_adaptive_demux_start_tasks: GST_MANIFEST_LOCK

write access, variable set to TRUE
gst_adaptive_demux_stop_tasks: no lock taken!

read accesses:
gst_adaptive_demux_stream_wait_manifest_update: GST_MANIFEST_LOCK
gst_adaptive_demux_stream_download_uri: stream->fragment_download_lock
gst_adaptive_demux_stream_download_header_fragment: no lock taken!
gst_adaptive_demux_stream_download_loop: sometimes GST_OBJECT_LOCK (demux) +
GST_MANIFEST_LOCK, sometimes GST_OBJECT_LOCK (demux), sometimes
fragment_download_lock

Seems that different readers use different locks and the writer
(gst_adaptive_demux_stop_tasks) does not use any lock!

What lock should be used for this variable? Or gst_adaptive_demux_stop_tasks
function should grab all 3 locks when setting it?

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