From 6c6384e9cd0c906c12bfbcd8c6c95d135d4632cc Mon Sep 17 00:00:00 2001
From: Guillaume Desmottes <guillaume.desmottes@onestream.live>
Date: Tue, 3 Oct 2023 09:15:11 +0200
Subject: [PATCH] gst-utils: prevent dead lock when requesting key unit

Sending the UpstreamForceKeyUnitEvent using gst_element_send_event()
internally takes the state lock. If appsink is pre-rolling we are also
holding the preroll lock.

This may result in a dead lock with the thread doing the state change as
this one takes the state lock and then the pre-roll lock.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1318>
---
 gstreamer-utils/src/streamproducer.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gstreamer-utils/src/streamproducer.rs b/gstreamer-utils/src/streamproducer.rs
index cf892cfe9..ceba37125 100644
--- a/gstreamer-utils/src/streamproducer.rs
+++ b/gstreamer-utils/src/streamproducer.rs
@@ -320,7 +320,9 @@ impl StreamProducer {
         drop(consumers);
 
         if needs_keyframe_request {
-            appsink.send_event(
+            // Do not use `gst_element_send_event()` as it takes the state lock which may lead to dead locks.
+            let pad = appsink.static_pad("sink").unwrap();
+            pad.push_event(
                 gst_video::UpstreamForceKeyUnitEvent::builder()
                     .all_headers(true)
                     .build(),