Fix a deadlock issue when shutting down ALSA cards.

[nageru] / audio_mixer.h

diff --git a/audio_mixer.h b/audio_mixer.h
index 23b020d43f77bb5765fd14efe55f18b588f6d75d..6e1d5a9458fbb1ef3d808d7cae162591a2ae878d 100644 (file)
--- a/audio_mixer.h
+++ b/audio_mixer.h
@@ -78,9 +78,14 @@ public:
        ~AudioMixer();
        void reset_resampler(DeviceSpec device_spec);
 
-       // frame_length is in TIMEBASE units.
-       void add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned num_samples, bmusb::AudioFormat audio_format, int64_t frame_length);
-       void add_silence(DeviceSpec device_spec, unsigned samples_per_frame, unsigned num_frames, int64_t frame_length);
+       // Add audio (or silence) to the given device's queue. Can return false if
+       // the lock wasn't successfully taken; if so, you should simply try again.
+       // (This is to avoid a deadlock where a card hangs on the mutex in add_audio()
+       // while we are trying to shut it down from another thread that also holds
+       // the mutex.) frame_length is in TIMEBASE units.
+       bool add_audio(DeviceSpec device_spec, const uint8_t *data, unsigned num_samples, bmusb::AudioFormat audio_format, int64_t frame_length);
+       bool add_silence(DeviceSpec device_spec, unsigned samples_per_frame, unsigned num_frames, int64_t frame_length);
+
        std::vector<float> get_output(double pts, unsigned num_samples, ResamplingQueue::RateAdjustmentPolicy rate_adjustment_policy);
 
        // See comments inside get_output().
@@ -219,7 +224,7 @@ private:
 
        unsigned num_cards;
 
-       mutable std::mutex audio_mutex;
+       mutable std::timed_mutex audio_mutex;
 
        AudioDevice video_cards[MAX_VIDEO_CARDS];  // Under audio_mutex.