Fix deadlock while recording MIDI controllers.

diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index c399b4e4381bff47430ea56cb8ca9176f8e70649..fe5c04be2585bf98b8f58e1dd3b653ddc98f6c01 100644 (file)
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -151,16 +151,9 @@ MidiRegion::clone (boost::shared_ptr<MidiSource> newsrc) const
        Evoral::MusicalTime const bend = bfc.from (_start + _length);
 
        {
+               /* Lock our source since we'll be reading from it.  write_to() will
+                  take a lock on newsrc. */
                Source::Lock lm (midi_source(0)->mutex());
-               /* ::write_to() will take the lock on newsrc.
-
-                  XXX taking the lock on our own source here seems
-                  partly sane and partly odd. We don't write the
-                  data to the newsrc from our source, but from
-                  the in memory copy. This whole thing (memory vs. disk, SMF
-                  versus MidiModel) is so f'ed up that its no wonder
-                  stuff is wierd sometimes.
-                */
                if (midi_source(0)->write_to (lm, newsrc, bbegin, bend)) {
                        return boost::shared_ptr<MidiRegion> ();
                }
@@ -425,9 +418,12 @@ MidiRegion::model_contents_changed ()
 {
        {
                /* Invalidate source iterator to force reading new contents even if the
-                  calls to read progress linearly. */
-               Glib::Threads::Mutex::Lock lm (midi_source(0)->mutex());
-               midi_source(0)->invalidate (lm);
+                  calls to read() progress linearly.  Try-lock only to avoid deadlock
+                  when called while writing with the source already locked. */
+               Glib::Threads::Mutex::Lock lm (midi_source(0)->mutex(), Glib::Threads::TRY_LOCK);
+               if (lm.locked()) {
+                       midi_source(0)->invalidate (lm);
+               }
        }
        send_change (PropertyChange (Properties::midi_data));
 }