Work around some deadlock issues when changing output card.

This feels pretty hackish and not necessarily safe, but it will
do for now. This should hopefully be a pretty rare operation.

diff --git a/mixer.cpp b/mixer.cpp
index e00fff89bd37ce3dd1f565f3eafbabb2ad9da4f0..855a73fcaf5969a63a4f27c8f487cf7273b84151 100644 (file)
--- a/mixer.cpp
+++ b/mixer.cpp
@@ -270,17 +270,26 @@ void Mixer::set_output_card(int card_index)
                CaptureCard *old_card = &cards[output_card_index];
                old_card->output->end_output();
 
-               old_card->capture->stop_dequeue_thread();
+               // Stop the fake card that we put into place.
+               // This needs to _not_ happen under the mutex, to avoid deadlock
+               // (delivering the last frame needs to take the mutex).
+               bmusb::CaptureInterface *fake_capture = old_card->capture.get();
+               lock.unlock();
+               fake_capture->stop_dequeue_thread();
+               lock.lock();
                old_card->capture = move(old_card->parked_capture);
                old_card->is_fake_capture = false;
                old_card->capture->start_bm_capture();
        }
 
        CaptureCard *card = &cards[card_index];
-       card->capture->stop_dequeue_thread();
+       bmusb::CaptureInterface *capture = card->capture.get();
+       lock.unlock();
+       capture->stop_dequeue_thread();
+       lock.lock();
        card->parked_capture = move(card->capture);
-       FakeCapture *capture = new FakeCapture(global_flags.width, global_flags.height, FAKE_FPS, OUTPUT_FREQUENCY, card_index, global_flags.fake_cards_audio);
-       configure_card(card_index, capture, /*is_fake_capture=*/true, card->output.release());
+       bmusb::CaptureInterface *fake_capture = new FakeCapture(global_flags.width, global_flags.height, FAKE_FPS, OUTPUT_FREQUENCY, card_index, global_flags.fake_cards_audio);
+       configure_card(card_index, fake_capture, /*is_fake_capture=*/true, card->output.release());
        card->queue_length_policy.reset(card_index);
        card->capture->start_bm_capture();
        card->output->start_output(bmdModeHD720p5994, pts_int);  // FIXME