Work around deadlock when destroying J2KEncoder with a full writer queue (#2784).v2.16.83

This feels like a hack, but I can't think of a nicer way to do it.

The interruption disable makes sense because when we destroy encoder threads
during a DCP encode (because a remote server goes away, for example) we don't
want any frames to be lost due to the encode thread being interrupted between
taking the frame off the queue and sending it to the writer.

When we're destroying the encoder we don't care about this, but I can't see
how you'd differentiate.

Maybe the encoder queue could have two lists: to-do and in-progress;
the encoder thread atomically moves a frame from to-do to in-progress,
but then how do you know when the in-progress ones are orphaned and need
to be re-added to the main queue.

You could make the writer return saying "no" if the queue is full (rather
than blocking and waiting for the queue to empty) but that seems wasteful
as then the frame would be re-encoded.

1 files changed, 83 insertions, 0 deletions

diff --git a/test/j2k_encoder_test.cc b/test/j2k_encoder_test.cc
new file mode 100644
index 000000000..bc3bd97b2
--- /dev/null
+++ b/test/j2k_encoder_test.cc
@@ -0,0 +1,83 @@
+/*
+    Copyright (C) 2024 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "lib/config.h"
+#include "lib/cross.h"
+#include "lib/image.h"
+#include "lib/j2k_encoder.h"
+#include "lib/player_video.h"
+#include "lib/raw_image_proxy.h"
+#include "lib/writer.h"
+#include "test.h"
+extern "C" {
+#include <libavutil/pixfmt.h>
+}
+#include <boost/test/unit_test.hpp>
+
+
+using std::make_shared;
+using std::weak_ptr;
+using boost::optional;
+
+
+BOOST_AUTO_TEST_CASE(j2k_encoder_deadlock_test)
+{
+	ConfigRestorer cr;
+
+	auto film = new_test_film2("j2k_encoder_deadlock_test");
+
+	/* Don't call ::start() on this Writer, so it can never write anything */
+	Writer writer(film, {});
+	writer.set_encoder_threads(4);
+
+	/* We want to test the case where the writer queue fills, and this can't happen unless there
+	 * are enough encoding threads (each of which will end up waiting for the writer to empty,
+	 * which will never happen).
+	 */
+	Config::instance()->set_master_encoding_threads(4);
+	J2KEncoder encoder(film, writer);
+	encoder.begin();
+
+	for (int i = 0; i < 26; ++i) {
+		auto image = make_shared<Image>(AV_PIX_FMT_RGB24, dcp::Size(1998, 1080), Image::Alignment::PADDED);
+		auto image_proxy = make_shared<RawImageProxy>(image);
+		encoder.encode(
+			std::make_shared<PlayerVideo>(
+				image_proxy,
+				Crop(),
+				optional<double>(),
+				dcp::Size(1998, 1080),
+				dcp::Size(1998, 1080),
+				Eyes::BOTH,
+				Part::WHOLE,
+				optional<ColourConversion>(),
+				VideoRange::VIDEO,
+				weak_ptr<Content>(),
+				optional<Frame>(),
+				false
+				),
+			{}
+			);
+	}
+
+	dcpomatic_sleep_seconds(10);
+}
+