[GStreamer][WebRTC] Avoid returning FLUSHING when it is not the case in GStreamerMedi...

https://bugs.webkit.org/show_bug.cgi?id=194087

Basically GstFlowCombiner was mostly designed for element that have 1 sinkpad and several srcpad
meaning that it makes sense that when any of the downstream pad is returning flushing, you should
return FLUSHING upstream. But in our case we have several sinkpads and FLUSHING should be returned
*only* if the internally linked srcpad is FLUSHING otherwise we might end up setting the upstream
source element task to PAUSED (because downstream returned flushing) on a branch that was not
flushing!

Patch by Thibault Saunier <tsaunier@igalia.com> on 2019-01-31
Reviewed by Philippe Normand.

This is a theorical race we can't really cover with tests.

* platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp:
(WebCore::webkitMediaStreamSrcChain):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@240782 268f45cc-cd09-0410-ab3c-d52691b4dbfc

diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index 8169133..8485d7d 100644 (file)
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,22 @@
+2019-01-31  Thibault Saunier  <tsaunier@igalia.com>
+
+        [GStreamer][WebRTC] Avoid returning FLUSHING when it is not the case in GStreamerMediaStreamSource
+        https://bugs.webkit.org/show_bug.cgi?id=194087
+
+        Basically GstFlowCombiner was mostly designed for element that have 1 sinkpad and several srcpad
+        meaning that it makes sense that when any of the downstream pad is returning flushing, you should
+        return FLUSHING upstream. But in our case we have several sinkpads and FLUSHING should be returned
+        *only* if the internally linked srcpad is FLUSHING otherwise we might end up setting the upstream
+        source element task to PAUSED (because downstream returned flushing) on a branch that was not
+        flushing!
+
+        Reviewed by Philippe Normand.
+
+        This is a theorical race we can't really cover with tests.
+
+        * platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp:
+        (WebCore::webkitMediaStreamSrcChain):
+

 2019-01-31  Zalan Bujtas  <zalan@apple.com>
 
         [LFC] Margin before/after/start/end initial value is 0 and not auto.
 2019-01-31  Zalan Bujtas  <zalan@apple.com>
 
         [LFC] Margin before/after/start/end initial value is 0 and not auto.

diff --git a/Source/WebCore/platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp b/Source/WebCore/platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp
index 927d986..c391c4c 100644 (file)
--- a/Source/WebCore/platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp
+++ b/Source/WebCore/platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp
@@ -368,11 +368,14 @@ typedef struct {
 
 static GstFlowReturn webkitMediaStreamSrcChain(GstPad* pad, GstObject* parent, GstBuffer* buffer)
 {
 
 static GstFlowReturn webkitMediaStreamSrcChain(GstPad* pad, GstObject* parent, GstBuffer* buffer)
 {

-    GstFlowReturn result;
+    GstFlowReturn result, chain_result;

     GRefPtr<WebKitMediaStreamSrc> self = adoptGRef(WEBKIT_MEDIA_STREAM_SRC(gst_object_get_parent(parent)));
 
     GRefPtr<WebKitMediaStreamSrc> self = adoptGRef(WEBKIT_MEDIA_STREAM_SRC(gst_object_get_parent(parent)));
 

-    result = gst_flow_combiner_update_pad_flow(self.get()->flowCombiner, pad,
-        gst_proxy_pad_chain_default(pad, GST_OBJECT(self.get()), buffer));
+    chain_result = gst_proxy_pad_chain_default(pad, GST_OBJECT(self.get()), buffer);
+    result = gst_flow_combiner_update_pad_flow(self.get()->flowCombiner, pad, chain_result);
+
+    if (result == GST_FLOW_FLUSHING)
+        return chain_result;

 
     return result;
 }
 
     return result;
 }