ardour/livetrax
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use a lock when dealing with PresentationInfo::Change emission

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This allows us to emit the signal while still marking further emissions as blocked.
This in turns prevents handlers from recursively calling themselves.
This commit is contained in:
Paul Davis 2017-01-27 22:15:10 +01:00
parent cc82fc675b
commit 2a95d79014
2 changed files with 19 additions and 9 deletions
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1
libs/ardour/ardour/presentation_info.h
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@ -265,6 +265,7 @@ class LIBARDOUR_API PresentationInfo : public PBD::Stateful
color_t _color; color_t _color;
static PBD::PropertyChange _pending_static_changes; static PBD::PropertyChange _pending_static_changes;
static Glib::Threads::Mutex static_signal_lock;
static int _change_signal_suspended; static int _change_signal_suspended;
static void send_static_change (const PBD::PropertyChange&); static void send_static_change (const PBD::PropertyChange&);
}; };

27
libs/ardour/presentation_info.cc
View File

@ -40,6 +40,7 @@ using std::string;
string PresentationInfo::state_node_name = X_("PresentationInfo"); string PresentationInfo::state_node_name = X_("PresentationInfo");
PBD::Signal1<void,PropertyChange const &> PresentationInfo::Change; PBD::Signal1<void,PropertyChange const &> PresentationInfo::Change;
Glib::Threads::Mutex PresentationInfo::static_signal_lock;
int PresentationInfo::_change_signal_suspended = 0; int PresentationInfo::_change_signal_suspended = 0;
PBD::PropertyChange PresentationInfo::_pending_static_changes; PBD::PropertyChange PresentationInfo::_pending_static_changes;
@ -60,24 +61,30 @@ PresentationInfo::suspend_change_signal ()
void void
PresentationInfo::unsuspend_change_signal () PresentationInfo::unsuspend_change_signal ()
{ {
PropertyChange pc = _pending_static_changes; Glib::Threads::Mutex::Lock lm (static_signal_lock);
/* XXX some possible race condition here; _pending_static_changes could if (g_atomic_int_get (const_cast<gint*> (&_change_signal_suspended)) == 1) {
* be reset by another thread before or after we decrement.
*/
if (g_atomic_int_dec_and_test (const_cast<gint*> (&_change_signal_suspended))) { if (!_pending_static_changes.empty()) {
if (!pc.empty()) {
_pending_static_changes.clear ();
std::cerr << "PI change (unsuspended): "; std::cerr << "PI change (unsuspended): ";
for (PropertyChange::const_iterator x = pc.begin(); x != pc.end(); ++x) { for (PropertyChange::const_iterator x = _pending_static_changes.begin(); x != _pending_static_changes.end(); ++x) {
std::cerr << g_quark_to_string (*x) << ','; std::cerr << g_quark_to_string (*x) << ',';
} }
std::cerr << '\n'; std::cerr << '\n';
Change (pc); /* EMIT SIGNAL */ /* emit the signal with further emissions still
* blocked, so that if the handlers modify other PI
* states, the signal for that won't be sent while
* they are handling this one.
*/
Change (_pending_static_changes); /* EMIT SIGNAL */
_pending_static_changes.clear ();
} }
g_atomic_int_add (const_cast<gint*>(&_change_signal_suspended), -1);
} }
} }
@ -88,6 +95,8 @@ PresentationInfo::send_static_change (const PropertyChange& what_changed)
return; return;
} }
Glib::Threads::Mutex::Lock lm (static_signal_lock);
if (g_atomic_int_get (&_change_signal_suspended)) { if (g_atomic_int_get (&_change_signal_suspended)) {
_pending_static_changes.add (what_changed); _pending_static_changes.add (what_changed);
return; return;