This is a note to let you know that I've just added the patch titled ALSA: usb-audio: Fix implicit sync clearance at stopping stream to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-usb-audio-fix-implicit-sync-clearance-at-stopping-stream.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 988cc17552606be67a956cf8cd6ff504cfc5d643 Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@xxxxxxx> Date: Mon, 26 Apr 2021 08:33:49 +0200 Subject: ALSA: usb-audio: Fix implicit sync clearance at stopping stream From: Takashi Iwai <tiwai@xxxxxxx> commit 988cc17552606be67a956cf8cd6ff504cfc5d643 upstream. The recent endpoint management change for implicit feedback mode added a clearance of ep->sync_sink (formerly ep->sync_slave) pointer at snd_usb_endpoint_stop() to assure no leftover for the feedback from the already stopped capture stream. This turned out to cause a regression, however, when full-duplex streams were running and only a capture was stopped. Because of the above clearance of ep->sync_sink pointer, no more feedback is done, hence the playback will stall. This patch fixes the ep->sync_sink clearance to be done only after all endpoints are released, for addressing the regression. Reported-and-tested-by: Lucas Endres <jaffa225man@xxxxxxxxx> Fixes: bf6313a0ff76 ("ALSA: usb-audio: Refactor endpoint management") Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210426063349.18601-1-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/endpoint.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -1442,11 +1442,11 @@ void snd_usb_endpoint_stop(struct snd_us if (snd_BUG_ON(!atomic_read(&ep->running))) return; - if (ep->sync_source) - WRITE_ONCE(ep->sync_source->sync_sink, NULL); - - if (!atomic_dec_return(&ep->running)) + if (!atomic_dec_return(&ep->running)) { + if (ep->sync_source) + WRITE_ONCE(ep->sync_source->sync_sink, NULL); stop_urbs(ep, false); + } } /** Patches currently in stable-queue which might be from tiwai@xxxxxxx are queue-5.11/alsa-usb-audio-fix-implicit-sync-clearance-at-stopping-stream.patch queue-5.11/alsa-usb-audio-add-midi-quirk-for-vox-tonelab-ex.patch