From 70f13a3ff3a96d9991e739a11a42bb62c0f71be6 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Wed, 8 Apr 2020 19:56:33 -0600
Subject: [PATCH] use RCU to manage JACK backend's container of ports

---
 libs/backends/jack/jack_audiobackend.cc |  9 +++++-
 libs/backends/jack/jack_audiobackend.h  |  4 +--
 libs/backends/jack/jack_portengine.cc   | 42 ++++++++++++++++++++-----
 3 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/libs/backends/jack/jack_audiobackend.cc b/libs/backends/jack/jack_audiobackend.cc
index 254dfa4147..37f5855cf1 100644
--- a/libs/backends/jack/jack_audiobackend.cc
+++ b/libs/backends/jack/jack_audiobackend.cc
@@ -64,6 +64,7 @@ JACKAudioBackend::JACKAudioBackend (AudioEngine& e, AudioBackendInfo& info, boos
 	, _target_systemic_output_latency (0)
 	, _current_sample_rate (0)
 	, _current_buffer_size (0)
+	, _jack_ports (new JackPorts)
 	, _session (0)
 {
 	_jack_connection->Connected.connect_same_thread (jack_connection_connection, boost::bind (&JACKAudioBackend::when_connected_to_jack, this));
@@ -72,7 +73,13 @@ JACKAudioBackend::JACKAudioBackend (AudioEngine& e, AudioBackendInfo& info, boos
 
 JACKAudioBackend::~JACKAudioBackend()
 {
-	_jack_ports.clear ();
+	{
+		RCUWriter<JackPorts> writer (_jack_ports);
+		boost::shared_ptr<JackPorts> jp = writer.get_copy ();
+		jp->clear ();
+	}
+
+	_jack_ports.flush ();
 }
 
 string
diff --git a/libs/backends/jack/jack_audiobackend.h b/libs/backends/jack/jack_audiobackend.h
index 1cde158025..449ad2ffc5 100644
--- a/libs/backends/jack/jack_audiobackend.h
+++ b/libs/backends/jack/jack_audiobackend.h
@@ -302,8 +302,8 @@ class JACKAudioBackend : public AudioBackend {
     static void _registration_callback (jack_port_id_t, int, void *);
     static void _connect_callback (jack_port_id_t, jack_port_id_t, int, void *);
 
-	typedef std::map<void*,boost::shared_ptr<JackPort> > JackPorts;
-	mutable JackPorts _jack_ports; /* can be modified in ::get_port_by_name () */
+    typedef std::map<void*,boost::shared_ptr<JackPort> > JackPorts;
+    mutable SerializedRCUManager<JackPorts> _jack_ports; /* can be modified in ::get_port_by_name () */
 
     void connect_callback (jack_port_id_t, jack_port_id_t, int);
 
diff --git a/libs/backends/jack/jack_portengine.cc b/libs/backends/jack/jack_portengine.cc
index 36da7c8962..18a9792ff2 100644
--- a/libs/backends/jack/jack_portengine.cc
+++ b/libs/backends/jack/jack_portengine.cc
@@ -182,16 +182,24 @@ JACKAudioBackend::get_port_by_name (const std::string& name) const
 		return PortEngine::PortPtr();
 	}
 
-	/* check if we have a shared_ptr<JackPort> for this already */
+	boost::shared_ptr<JackPorts> ports = _jack_ports.reader ();
 
-	JackPorts::const_iterator i =  _jack_ports.find (jack_port);
+	JackPorts::const_iterator i =  ports->find (jack_port);
 
-	if (i != _jack_ports.end()) {
+	if (i != ports->end()) {
 		return i->second;
 	}
 
-	boost::shared_ptr<JackPort> jp (new JackPort (jack_port));
-	_jack_ports.insert (std::make_pair (jack_port, jp));
+	boost::shared_ptr<JackPort> jp;
+
+	{
+		RCUWriter<JackPorts> writer (_jack_ports);
+		boost::shared_ptr<JackPorts> ports = writer.get_copy();
+		jp.reset (new JackPort (jack_port));
+		ports->insert (std::make_pair (jack_port, jp));
+	}
+
+	_jack_ports.flush ();
 
 	return jp;
 }
@@ -505,9 +513,18 @@ JACKAudioBackend::register_port (const std::string& shortname, ARDOUR::DataType
 		return PortEngine::PortPtr();
 	}
 
-	 boost::shared_ptr<JackPort> jp (new JackPort (jack_port));
+	boost::shared_ptr<JackPort> jp;
 
-	 _jack_ports.insert (std::make_pair (jack_port, jp));
+	{
+		RCUWriter<JackPorts> writer (_jack_ports);
+		boost::shared_ptr<JackPorts> ports = writer.get_copy();
+
+		jp.reset (new JackPort (jack_port));
+
+		ports->insert (std::make_pair (jack_port, jp));
+	}
+
+	_jack_ports.flush();
 
 	 return jp;
 }
@@ -517,7 +534,16 @@ JACKAudioBackend::unregister_port (PortHandle port)
 {
 	GET_PRIVATE_JACK_POINTER (_priv_jack);
 	boost::shared_ptr<JackPort> jp = boost::dynamic_pointer_cast<JackPort>(port);
-	_jack_ports.erase (jp->jack_ptr);
+
+	{
+		RCUWriter<JackPorts> writer (_jack_ports);
+		boost::shared_ptr<JackPorts> ports = writer.get_copy();
+
+		ports->erase (jp->jack_ptr);
+	}
+
+	_jack_ports.flush ();
+
 	(void) jack_port_unregister (_priv_jack, jp->jack_ptr);
 }