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gstrtspsrc: Do not emit signal 'no-more-pads' too early

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Due to race condition it was previously possible that
gst_element_add_pad was not completed for each RTSP stream before
signal 'no-more-pads' was emitted.

Race condition explained:
Lets say two RTSP streams are created: Video and Audio.
1. Callback new_manager_pad is called for the Video stream =>
   stream->added=TRUE.
   all_added=FALSE because both streams are not yet added.
   Call gst_element_add_pad and emit signal 'pad-added' for Video stream.
2. Callback new_manager_pad is called for Audio stream =>
   stream->added=TRUE.
   all_added=TRUE because both streams are added.
   Call gst_element_add_pad and emit signal 'pad-added' for Audio stream.
3. Lets say gst_element_add_pad for the audio stream completes before
   the video stream. Since the audio stream already has all_added==TRUE
   this will result in the signal 'no-more-pads' to be emitted before
   gst_element_add_pad for the video stream is completed.

Solution is to move the logic that sets added=True and checks if all
streams are added to after gst_element_add_pad. This will make sure
signal 'no-more-pads' is not emitted until all code in
gst_element_add_pad is completed for all streams.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8832>
This commit is contained in:
Gustav Fahlen 2025-04-10 11:31:28 +02:00 committed by GStreamer Marge Bot
parent c4bfa73391
commit e649072584
1 changed files with 23 additions and 19 deletions
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42
subprojects/gst-plugins-good/gst/rtsp/gstrtspsrc.c
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@ -3910,25 +3910,6 @@ new_manager_pad (GstElement * manager, GstPad * pad, GstRTSPSrc * src)
/* save SSRC */
stream->ssrc = ssrc;
/* we'll add it later see below */
stream->added = TRUE;
/* check if we added all streams */
all_added = TRUE;
for (ostreams = src->streams; ostreams; ostreams = g_list_next (ostreams)) {
GstRTSPStream *ostream = (GstRTSPStream *) ostreams->data;
GST_DEBUG_OBJECT (src, "stream %p, container %d, added %d, setup %d",
ostream, ostream->container, ostream->added, ostream->setup);
/* if we find a stream for which we did a setup that is not added, we
* need to wait some more */
if (ostream->setup && !ostream->added) {
all_added = FALSE;
break;
}
}
GST_RTSP_STATE_UNLOCK (src);
/* create a new pad we will use to stream to */
@ -3967,6 +3948,29 @@ new_manager_pad (GstElement * manager, GstPad * pad, GstRTSPSrc * src)
gst_element_add_pad (GST_ELEMENT_CAST (src), stream->srcpad);
}
GST_RTSP_STATE_LOCK (src);
/* Setting added after gst_element_add_pad will make
sure callbacks for signal 'pad-added' will always
finish before signal 'no-more-pads' is executed. */
stream->added = TRUE;
/* check if we added all streams */
all_added = TRUE;
for (ostreams = src->streams; ostreams; ostreams = g_list_next (ostreams)) {
GstRTSPStream *ostream = (GstRTSPStream *) ostreams->data;
GST_DEBUG_OBJECT (src, "stream %p, container %d, added %d, setup %d",
ostream, ostream->container, ostream->added, ostream->setup);
/* if we find a stream for which we did a setup that is not added, we
* need to wait some more */
if (ostream->setup && !ostream->added) {
all_added = FALSE;
break;
}
}
GST_RTSP_STATE_UNLOCK (src);
if (all_added) {
GST_DEBUG_OBJECT (src, "We added all streams");
/* when we get here, all stream are added and we can fire the no-more-pads