fix deadlock in mutex'ed PresentationInfo code

[ardour.git] / libs / ardour / presentation_info.cc

diff --git a/libs/ardour/presentation_info.cc b/libs/ardour/presentation_info.cc
index 31f595a8c2fc9fdfabb0150049885b9a5ff844c3..64d2a35828ca3a2b9d2d6fc634689ff58bb36c33 100644 (file)
--- a/libs/ardour/presentation_info.cc
+++ b/libs/ardour/presentation_info.cc
@@ -61,14 +61,22 @@ PresentationInfo::suspend_change_signal ()
 void
 PresentationInfo::unsuspend_change_signal ()
 {
-       Glib::Threads::Mutex::Lock lm (static_signal_lock);
-
        if (g_atomic_int_get (const_cast<gint*> (&_change_signal_suspended)) == 1) {
 
-               if (!_pending_static_changes.empty()) {
+               /* atomically grab currently pending flags */
+
+               PropertyChange pc;
+
+               {
+                       Glib::Threads::Mutex::Lock lm (static_signal_lock);
+                       pc = _pending_static_changes;
+                       _pending_static_changes.clear ();
+               }
+
+               if (!pc.empty()) {
 
                        std::cerr << "PI change (unsuspended): ";
-                       for (PropertyChange::const_iterator x = _pending_static_changes.begin(); x != _pending_static_changes.end(); ++x) {
+                       for (PropertyChange::const_iterator x = pc.begin(); x != pc.end(); ++x) {
                                std::cerr << g_quark_to_string (*x) << ',';
                        }
                        std::cerr << '\n';
@@ -79,9 +87,7 @@ PresentationInfo::unsuspend_change_signal ()
                         * they are handling this one.
                         */
 
-                       Change (_pending_static_changes); /* EMIT SIGNAL */
-
-                       _pending_static_changes.clear ();
+                       Change (pc); /* EMIT SIGNAL */
                }
 
                g_atomic_int_add (const_cast<gint*>(&_change_signal_suspended), -1);
@@ -95,9 +101,9 @@ PresentationInfo::send_static_change (const PropertyChange& what_changed)
                return;
        }
 
-       Glib::Threads::Mutex::Lock lm (static_signal_lock);
 
        if (g_atomic_int_get (&_change_signal_suspended)) {
+               Glib::Threads::Mutex::Lock lm (static_signal_lock);
                _pending_static_changes.add (what_changed);
                return;
        }