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Fix deletion of VCA with slaved controls.

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The crashed previously because:
 A VCA is-a Automatable is-a Evoral::ControlSet

 After VCA's d'tor completes ~Automatable runs and emits signal to
 DropReferences of all master-controls.

 This in turn calls SlavableAutomationControl::master_going_away()
 for slaved parameters for the given master-control

 In ::master_going_away() the weak-pointer reference to the master's
 AutomationControl (owned by the destroyed VCA) is still valid.

 Execution is in the d'tor of Automatable which is-a ControlSet and
 the ContolSet keeps a reference to the Control and hence also to the
 AutomationControl which is-a Evoral::Control.

 So master_going_away() locks a boost::shared_ptr<ARDOUR::AutomationControl>
 which is actually the MuteControl owned by the VCA.
 It calls SlavableAutomationControl::remove_master() which
 in turn calls MuteControl::pre_remove_master() which uses the
 MuteMaster API to retrieve the value. The MuteMaster however is the
 VCA that has just been destroyed.


The solution is twofold:
 1) emit "drop_references" from the VCA d'tor itself,
    before the VCA is destroyed.

 2) disconnect a slaved control from the master's drop_references signal
    when un-assigning a master-control.
This commit is contained in:
Robin Gareus 2017-06-09 22:54:09 +02:00
parent 8502aa18c5
commit a1b4f9b8ab
4 changed files with 14 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

2
libs/ardour/ardour/automation_control.h
View file

@ -62,7 +62,7 @@ class LIBARDOUR_API AutomationControl
PBD::Controllable::Flag flags=PBD::Controllable::Flag (0)
);
~AutomationControl ();
virtual ~AutomationControl ();
boost::shared_ptr<AutomationList> alist() const {
return boost::dynamic_pointer_cast<AutomationList>(_list);

4
libs/ardour/ardour/slavable_automation_control.h
View file

@ -36,7 +36,7 @@ class LIBARDOUR_API SlavableAutomationControl : public AutomationControl
PBD::Controllable::Flag flags=PBD::Controllable::Flag (0)
);
~SlavableAutomationControl ();
virtual ~SlavableAutomationControl ();
double get_value () const;
@ -110,7 +110,7 @@ class LIBARDOUR_API SlavableAutomationControl : public AutomationControl
mutable Glib::Threads::RWLock master_lock;
typedef std::map<PBD::ID,MasterRecord> Masters;
Masters _masters;
PBD::ScopedConnectionList masters_connections;
std::map<boost::weak_ptr<AutomationControl>, PBD::ScopedConnection> masters_connections;
void master_going_away (boost::weak_ptr<AutomationControl>);
double get_value_locked() const;

7
libs/ardour/slavable_automation_control.cc
View file

@ -222,8 +222,10 @@ SlavableAutomationControl::add_master (boost::shared_ptr<AutomationControl> m, b
avoiding holding a reference to the control in the binding
itself.
*/
m->DropReferences.connect_same_thread (masters_connections, boost::bind (&SlavableAutomationControl::master_going_away, this, boost::weak_ptr<AutomationControl>(m)));
assert (masters_connections.find (boost::weak_ptr<AutomationControl>(m)) == masters_connections.end());
PBD::ScopedConnection con;
m->DropReferences.connect_same_thread (con, boost::bind (&SlavableAutomationControl::master_going_away, this, boost::weak_ptr<AutomationControl>(m)));
masters_connections[boost::weak_ptr<AutomationControl>(m)] = con;
/* Store the connection inside the MasterRecord, so
that when we destroy it, the connection is destroyed
@ -326,6 +328,7 @@ SlavableAutomationControl::master_going_away (boost::weak_ptr<AutomationControl>
void
SlavableAutomationControl::remove_master (boost::shared_ptr<AutomationControl> m)
{
masters_connections.erase (boost::weak_ptr<AutomationControl>(m));
pre_remove_master (m);
{

6
libs/ardour/vca.cc
View file

@ -91,6 +91,12 @@ VCA::init ()
VCA::~VCA ()
{
DEBUG_TRACE (DEBUG::Destruction, string_compose ("delete VCA %1\n", number()));
{
Glib::Threads::Mutex::Lock lm (_control_lock);
for (Controls::const_iterator li = _controls.begin(); li != _controls.end(); ++li) {
boost::dynamic_pointer_cast<AutomationControl>(li->second)->drop_references ();
}
}
{
Glib::Threads::Mutex::Lock lm (number_lock);
if (_number == next_number - 1) {