Fix a deadlock in Futatabi when using MIDI devices.

[nageru] / shared / midi_device.h

diff --git a/shared/midi_device.h b/shared/midi_device.h
index a9f33d65c6516d835d909f3fa2407fa200b115c6..5b1c3ade4c4ea8c884f9b131f5caa735b082268c 100644 (file)
--- a/shared/midi_device.h
+++ b/shared/midi_device.h
@@ -47,7 +47,7 @@ public:
 
        void update_lights(const std::map<LightKey, uint8_t> &active_lights)
        {
-               std::lock_guard<std::mutex> lock(mu);
+               std::lock_guard<std::recursive_mutex> lock(mu);
                update_lights_lock_held(active_lights);
        }
 
@@ -60,8 +60,10 @@ private:
        std::atomic<bool> should_quit{false};
        int should_quit_fd;
 
-       mutable std::mutex mu;
-       MIDIReceiver *receiver;  // Under <mu>.
+       // Recursive because the MIDI receiver may update_lights() back while we are sending it stuff.
+       // TODO: Do we need this anymore after receiver is not under the lock?
+       mutable std::recursive_mutex mu;
+       MIDIReceiver *receiver;  // _Not_ under <mu>; everything on it should be thread-safe.
 
        std::thread midi_thread;
        std::map<LightKey, uint8_t> current_light_status;  // Keyed by note number. Under <mu>.