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Fix deadlock/race introduced in aaf301321

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Port::_connections_lock must not be locked when calling
port_engine.connect().
This commit is contained in:
Robin Gareus 2023-05-27 14:18:31 +02:00
parent abd27b765e
commit 10b2380b14
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 35 additions and 25 deletions
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60
libs/ardour/port.cc
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@ -714,54 +714,64 @@ Port::has_ext_connection () const
int
Port::reconnect ()
{
/* caller must hold process lock; intended to be used only after reestablish() */
int count = 0;
std::string const bid (AudioEngine::instance()->backend_id (receives_input ()));
Glib::Threads::RWLock::WriterLock lm (_connections_lock);
std::vector <std::string> c_int, c_ext, f_int, f_ext;
Glib::Threads::RWLock::ReaderLock lm (_connections_lock);
if (_ext_connections.find (bid) != _ext_connections.end ()) {
if (_int_connections.empty () && _ext_connections[bid].empty ()) {
return 0; /* OK */
}
count = _int_connections.size() + _ext_connections[bid].size();
c_int.insert (c_int.end(), _int_connections.begin(), _int_connections.end());
c_ext.insert (c_ext.end(), _ext_connections.at(bid).begin(), _ext_connections.at(bid).end());
} else {
if (_int_connections.empty ()) {
return 0; /* OK */
}
count = _int_connections.size();
c_int.insert (c_int.end(), _int_connections.begin(), _int_connections.end());
}
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() Connect %1 to %2 destinations\n",name(), count));
/* Must hold the lock while calling port_engine.connect. It could lead to deadlock:
*
* XXBackend::main_process_thread -> PortManager::connect_callback
* -> Port::port_connected_or_disconnected -> Port::insert_connection -> take WriterLock
*/
lm.release ();
count = 0;
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() Connect %1 to %2 destinations\n",name(), c_int.size () + c_ext.size ()));
ConnectionSet::iterator i = _int_connections.begin();
while (i != _int_connections.end()) {
ConnectionSet::iterator current = i++;
if (connect_internal (*current)) {
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() failed to connect %1 to %2\n", name(), (*current)));
_int_connections.erase (current);
int count = 0;
for (auto const& c : c_int) {
if (connect_internal (c)) {
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() failed to connect %1 to %2\n", name(), (c)));
f_int.push_back (c);
} else {
++count;
}
}
if (_ext_connections.find (bid) != _ext_connections.end ()) {
i = _ext_connections[bid].begin();
while (i != _ext_connections[bid].end()) {
ConnectionSet::iterator current = i++;
if (connect_internal (*current)) {
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() failed to connect %1 to %2\n", name(), (*current)));
_ext_connections[bid].erase (current);
} else {
++count;
}
for (auto const& c : c_ext) {
if (connect_internal (c)) {
DEBUG_TRACE (DEBUG::Ports, string_compose ("Port::reconnect() failed to connect %1 to %2\n", name(), (c)));
f_ext.push_back (c);
} else {
++count;
}
}
lm.acquire ();
for (auto const& c : f_int) {
_int_connections.erase (c);
}
for (auto const& c : f_ext) {
_ext_connections[bid].erase (c);
}
return count == 0 ? -1 : 0;
}