From 6425b4f9f56f5b98124cf7b006ede4ec8d86a567 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Wed, 14 Dec 2016 08:15:33 +0100
Subject: [PATCH] output/MultipleOutputs: parallelize AudioOutput destruction

Reduce latency by stopping all AudioOutputs asynchronously.
---
 src/output/Internal.hxx        |  3 ++-
 src/output/MultipleOutputs.cxx |  5 ++++-
 src/output/OutputControl.cxx   | 13 +++++++++++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/output/Internal.hxx b/src/output/Internal.hxx
index a6f0d9d2e..6f45a44e7 100644
--- a/src/output/Internal.hxx
+++ b/src/output/Internal.hxx
@@ -283,7 +283,8 @@ public:
 	void StartThread();
 	void StopThread();
 
-	void Finish();
+	void BeginDestroy();
+	void FinishDestroy();
 
 	bool IsOpen() const {
 		return open;
diff --git a/src/output/MultipleOutputs.cxx b/src/output/MultipleOutputs.cxx
index d5b6340d0..6f846faaa 100644
--- a/src/output/MultipleOutputs.cxx
+++ b/src/output/MultipleOutputs.cxx
@@ -43,8 +43,11 @@ MultipleOutputs::MultipleOutputs(MixerListener &_mixer_listener)
 
 MultipleOutputs::~MultipleOutputs()
 {
+	/* parallel destruction */
 	for (auto i : outputs)
-		i->Finish();
+		i->BeginDestroy();
+	for (auto i : outputs)
+		i->FinishDestroy();
 }
 
 static AudioOutput *
diff --git a/src/output/OutputControl.cxx b/src/output/OutputControl.cxx
index e7221a171..01bca7ae8 100644
--- a/src/output/OutputControl.cxx
+++ b/src/output/OutputControl.cxx
@@ -274,13 +274,22 @@ AudioOutput::StopThread()
 }
 
 void
-AudioOutput::Finish()
+AudioOutput::BeginDestroy()
 {
 	if (mixer != nullptr)
 		mixer_auto_close(mixer);
 
+	if (thread.IsDefined()) {
+		const ScopeLock protect(mutex);
+		CommandAsync(Command::KILL);
+	}
+}
+
+void
+AudioOutput::FinishDestroy()
+{
 	if (thread.IsDefined())
-		StopThread();
+		thread.Join();
 
 	audio_output_free(this);
 }