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Prevent deadlock when disconnecting

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The backend holds `_port_callback_mutex` while disconnecting ports.
In some cases disconnecting a port can drop the last reference
resulting in a port-deletion from the connection handler.
This in turn will eventually aquire the `_port_callback_mutex`
and deadlock.

This is now circumvented by using atomic operations instead of
taking a lock to set the `_port_change_flag`.

The flag is also used to trigger a latency update in some cases,
atomic is preferable to taking a lock to set this flag.

--

Full bt: https://paste.debian.net/1184056/
Short:

#1  in pthread_mutex_lock ()
#2  in ARDOUR::PortEngineSharedImpl::port_connect_add_remove_callback()
#3  in ARDOUR::BackendPort::~BackendPort()
#4  in ARDOUR::DummyPort::~DummyPort()
#6  in ARDOUR::DummyAudioPort::~DummyAudioPort()
#7  in boost::checked_delete<ARDOUR::BackendPort>(ARDOUR::BackendPort*)
#12 in boost::shared_ptr<ARDOUR::ProtoPort>::reset()
#13 in ARDOUR::Port::drop()
#14 in ARDOUR::Port::~Port()
#15 in ARDOUR::AudioPort::~AudioPort()
#17 in ARDOUR::AudioEngine::add_pending_port_deletion(ARDOUR::Port*)
#20 in boost::detail::sp_counted_base::release()
#37 in ARDOUR::PortManager::connect_callback() at libs/ardour/port_manager.cc:788
#38 in ARDOUR::DummyAudioBackend::main_process_thread() at libs/backends/dummy/dummy_audiobackend.cc:1018
This commit is contained in:
Robin Gareus 2021-02-04 21:04:40 +01:00
parent 30da8c00b5
commit 634d325e5d
No known key found for this signature in database
GPG key ID: A090BCE02CF57F04
7 changed files with 21 additions and 29 deletions
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7
libs/ardour/ardour/port_engine_shared.h
View file

@ -183,7 +183,8 @@ protected:
std::vector<PortConnectData *> _port_connection_queue; std::vector<PortConnectData *> _port_connection_queue;
pthread_mutex_t _port_callback_mutex; pthread_mutex_t _port_callback_mutex;
bool _port_change_flag;
gint _port_change_flag; /* atomic */
void port_connect_callback (const std::string& a, const std::string& b, bool conn) { void port_connect_callback (const std::string& a, const std::string& b, bool conn) {
pthread_mutex_lock (&_port_callback_mutex); pthread_mutex_lock (&_port_callback_mutex);
@ -192,9 +193,7 @@ protected:
} }
void port_connect_add_remove_callback () { void port_connect_add_remove_callback () {
pthread_mutex_lock (&_port_callback_mutex); g_atomic_int_set (&_port_change_flag, 1);
_port_change_flag = true;
pthread_mutex_unlock (&_port_callback_mutex);
} }
virtual void update_system_port_latencies (); virtual void update_system_port_latencies ();

4
libs/ardour/port_engine_shared.cc
View file

@ -190,7 +190,7 @@ BackendPort::update_connected_latency (bool for_playback)
PortEngineSharedImpl::PortEngineSharedImpl (PortManager& mgr, std::string const & str) PortEngineSharedImpl::PortEngineSharedImpl (PortManager& mgr, std::string const & str)
: _instance_name (str) : _instance_name (str)
, _port_change_flag (false) , _port_change_flag (0)
, _portmap (new PortMap) , _portmap (new PortMap)
, _ports (new PortIndex) , _ports (new PortIndex)
{ {
@ -435,8 +435,8 @@ PortEngineSharedImpl::clear_ports ()
_ports.flush (); _ports.flush ();
_portmap.flush (); _portmap.flush ();
g_atomic_int_set (&_port_change_flag, 0);
pthread_mutex_lock (&_port_callback_mutex); pthread_mutex_lock (&_port_callback_mutex);
_port_change_flag = false;
_port_connection_queue.clear(); _port_connection_queue.clear();
pthread_mutex_unlock (&_port_callback_mutex); pthread_mutex_unlock (&_port_callback_mutex);
} }

5
libs/backends/alsa/alsa_audiobackend.cc
View file

@ -984,7 +984,7 @@ AlsaAudioBackend::_start (bool for_latency_measurement)
engine.reconnect_ports (); engine.reconnect_ports ();
_run = true; _run = true;
_port_change_flag = false; g_atomic_int_set (&_port_change_flag, 0);
if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, PBD_RT_PRI_MAIN, PBD_RT_STACKSIZE_PROC, if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, PBD_RT_PRI_MAIN, PBD_RT_STACKSIZE_PROC,
&_main_thread, pthread_process, this)) &_main_thread, pthread_process, this))
@ -2039,9 +2039,8 @@ AlsaAudioBackend::main_process_thread ()
bool connections_changed = false; bool connections_changed = false;
bool ports_changed = false; bool ports_changed = false;
if (!pthread_mutex_trylock (&_port_callback_mutex)) { if (!pthread_mutex_trylock (&_port_callback_mutex)) {
if (_port_change_flag) { if (g_atomic_int_compare_and_exchange (&_port_change_flag, 1, 0)) {
ports_changed = true; ports_changed = true;
_port_change_flag = false;
} }
if (!_port_connection_queue.empty ()) { if (!_port_connection_queue.empty ()) {
connections_changed = true; connections_changed = true;

15
libs/backends/coreaudio/coreaudio_backend.cc
View file

@ -640,7 +640,7 @@ CoreAudioBackend::_start (bool for_latency_measurement)
_preinit = true; _preinit = true;
_run = true; _run = true;
_port_change_flag = false; g_atomic_int_set (&_port_change_flag, 0);
if (_midi_driver_option == _("CoreMidi")) { if (_midi_driver_option == _("CoreMidi")) {
_midiio->set_enabled(true); _midiio->set_enabled(true);
@ -698,7 +698,7 @@ CoreAudioBackend::_start (bool for_latency_measurement)
engine.reconnect_ports (); engine.reconnect_ports ();
// force an initial registration_callback() & latency re-compute // force an initial registration_callback() & latency re-compute
_port_change_flag = true; g_atomic_int_set (&_port_change_flag, 1);
pre_process (); pre_process ();
_dsp_load_calc.reset (); _dsp_load_calc.reset ();
@ -988,7 +988,7 @@ CoreAudioBackend::coremidi_rediscover()
#ifndef NDEBUG #ifndef NDEBUG
printf("unregister MIDI Output: %s\n", (*it)->name().c_str()); printf("unregister MIDI Output: %s\n", (*it)->name().c_str());
#endif #endif
_port_change_flag = true; g_atomic_int_set (&_port_change_flag, 1);
unregister_port((*it)); unregister_port((*it));
it = _system_midi_out.erase(it); it = _system_midi_out.erase(it);
} }
@ -1008,7 +1008,7 @@ CoreAudioBackend::coremidi_rediscover()
#ifndef NDEBUG #ifndef NDEBUG
printf("unregister MIDI Input: %s\n", (*it)->name().c_str()); printf("unregister MIDI Input: %s\n", (*it)->name().c_str());
#endif #endif
_port_change_flag = true; g_atomic_int_set (&_port_change_flag, 1);
unregister_port((*it)); unregister_port((*it));
it = _system_midi_in.erase(it); it = _system_midi_in.erase(it);
} }
@ -1034,7 +1034,7 @@ CoreAudioBackend::coremidi_rediscover()
BackendPortPtr pp = boost::dynamic_pointer_cast<BackendPort>(p); BackendPortPtr pp = boost::dynamic_pointer_cast<BackendPort>(p);
pp->set_hw_port_name(_midiio->port_name(i, true)); pp->set_hw_port_name(_midiio->port_name(i, true));
_system_midi_in.push_back(pp); _system_midi_in.push_back(pp);
_port_change_flag = true; g_atomic_int_set (&_port_change_flag, 1);
} }
for (size_t i = 0; i < _midiio->n_midi_outputs(); ++i) { for (size_t i = 0; i < _midiio->n_midi_outputs(); ++i) {
@ -1057,7 +1057,7 @@ CoreAudioBackend::coremidi_rediscover()
BackendPortPtr pp = boost::dynamic_pointer_cast<BackendPort>(p); BackendPortPtr pp = boost::dynamic_pointer_cast<BackendPort>(p);
pp->set_hw_port_name(_midiio->port_name(i, false)); pp->set_hw_port_name(_midiio->port_name(i, false));
_system_midi_out.push_back(pp); _system_midi_out.push_back(pp);
_port_change_flag = true; g_atomic_int_set (&_port_change_flag, 1);
} }
@ -1229,9 +1229,8 @@ CoreAudioBackend::pre_process ()
bool connections_changed = false; bool connections_changed = false;
bool ports_changed = false; bool ports_changed = false;
if (!pthread_mutex_trylock (&_port_callback_mutex)) { if (!pthread_mutex_trylock (&_port_callback_mutex)) {
if (_port_change_flag) { if (g_atomic_int_compare_and_exchange (&_port_change_flag, 1, 0)) {
ports_changed = true; ports_changed = true;
_port_change_flag = false;
} }
if (!_port_connection_queue.empty ()) { if (!_port_connection_queue.empty ()) {
connections_changed = true; connections_changed = true;

5
libs/backends/dummy/dummy_audiobackend.cc
View file

@ -460,7 +460,7 @@ DummyAudioBackend::_start (bool /*for_latency_measurement*/)
} }
engine.reconnect_ports (); engine.reconnect_ports ();
_port_change_flag = false; g_atomic_int_set (&_port_change_flag, 0);
if (pbd_pthread_create (PBD_RT_STACKSIZE_PROC, &_main_thread, pthread_process, this)) { if (pbd_pthread_create (PBD_RT_STACKSIZE_PROC, &_main_thread, pthread_process, this)) {
PBD::error << _("DummyAudioBackend: cannot start.") << endmsg; PBD::error << _("DummyAudioBackend: cannot start.") << endmsg;
@ -1006,9 +1006,8 @@ DummyAudioBackend::main_process_thread ()
bool connections_changed = false; bool connections_changed = false;
bool ports_changed = false; bool ports_changed = false;
if (!pthread_mutex_trylock (&_port_callback_mutex)) { if (!pthread_mutex_trylock (&_port_callback_mutex)) {
if (_port_change_flag) { if (g_atomic_int_compare_and_exchange (&_port_change_flag, 1, 0)) {
ports_changed = true; ports_changed = true;
_port_change_flag = false;
} }
if (!_port_connection_queue.empty ()) { if (!_port_connection_queue.empty ()) {
connections_changed = true; connections_changed = true;

7
libs/backends/portaudio/portaudio_backend.cc
View file

@ -636,8 +636,6 @@ PortAudioBackend::_start (bool for_latency_measurement)
_measure_latency = for_latency_measurement; _measure_latency = for_latency_measurement;
_port_change_flag = false;
if (_midi_driver_option == winmme_driver_name) { if (_midi_driver_option == winmme_driver_name) {
_midiio->set_enabled(true); _midiio->set_enabled(true);
//_midiio->set_port_changed_callback(midi_port_change, this); //_midiio->set_port_changed_callback(midi_port_change, this);
@ -674,7 +672,7 @@ PortAudioBackend::_start (bool for_latency_measurement)
_run = true; _run = true;
engine.reconnect_ports (); engine.reconnect_ports ();
_port_change_flag = false; g_atomic_int_set (&_port_change_flag, 0);
_dsp_calc.reset (); _dsp_calc.reset ();
@ -1728,9 +1726,8 @@ PortAudioBackend::process_port_connection_changes ()
bool connections_changed = false; bool connections_changed = false;
bool ports_changed = false; bool ports_changed = false;
if (!pthread_mutex_trylock (&_port_callback_mutex)) { if (!pthread_mutex_trylock (&_port_callback_mutex)) {
if (_port_change_flag) { if (g_atomic_int_compare_and_exchange (&_port_change_flag, 1, 0)) {
ports_changed = true; ports_changed = true;
_port_change_flag = false;
} }
if (!_port_connection_queue.empty ()) { if (!_port_connection_queue.empty ()) {
connections_changed = true; connections_changed = true;

7
libs/backends/pulseaudio/pulseaudio_backend.cc
View file

@ -625,7 +625,7 @@ PulseAudioBackend::_start (bool /*for_latency_measurement*/)
engine.reconnect_ports (); engine.reconnect_ports ();
_run = true; _run = true;
_port_change_flag = false; g_atomic_int_set (&_port_change_flag, 0);
if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, PBD_RT_PRI_MAIN, PBD_RT_STACKSIZE_PROC, if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, PBD_RT_PRI_MAIN, PBD_RT_STACKSIZE_PROC,
&_main_thread, pthread_process, this)) { &_main_thread, pthread_process, this)) {
@ -1104,9 +1104,8 @@ PulseAudioBackend::main_process_thread ()
bool connections_changed = false; bool connections_changed = false;
bool ports_changed = false; bool ports_changed = false;
if (!pthread_mutex_trylock (&_port_callback_mutex)) { if (!pthread_mutex_trylock (&_port_callback_mutex)) {
if (_port_change_flag) { if (g_atomic_int_compare_and_exchange (&_port_change_flag, 1, 0)) {
ports_changed = true; ports_changed = true;
_port_change_flag = false;
} }
if (!_port_connection_queue.empty ()) { if (!_port_connection_queue.empty ()) {
connections_changed = true; connections_changed = true;