Thank you for your contribution! Sashiko AI review found 2 potential issues to consider: - [Medium] ALSA: virtio: premature ACK admission in virtsnd_pcm_reset() during prepare - [Low] ALSA: virtio: misplaced Fixes trailer and inaccurate commit message --
commit d7d32fabac0905c34c390dcb86edfd7a2dc6b2c7 Author: Joonho Lee <[email protected]> > ALSA: virtio: Propagate PCM send failures through ACK > > virtsnd_pcm_msg_send() can fail while queueing a transfer. Restore the > failed message's length and notify the device about earlier messages > queued by the same call, so they do not remain stranded. > > Propagate errors through the indirect transfer callback and commit its > private cursor only after successful submission. Genuine transfer errors > arm stop_operating and return -EPIPE so ALSA can retire the stream. > > Close ACK admission under the PCM stream lock before sleeping teardown. > Keep the prepared state protected by the substream lock and reject ACK > through prepare and parameter changes. Reopen admission in the reset > callback while the core holds the PCM lock for its pointer rebase. An > ACK racing with teardown returns -EBADFD and preserves stop state. > > Keep the polling feature path unchanged. > > Fixes: fe981e67568c ("ALSA: virtio: use ack callback") > > Reject a stopped playback ACK before the XRUN path can rearm > stop_operating. For capture, allow the ordinary stopped tail only during > DRAINING and only while no transfer XRUN is latched. > > Latch a transfer failure before stopping PCM work. Once core reports the > member XRUN, ACK returns -EBADFD to avoid another linked XRUN. ACK during > prepare remains rejected until the core state reaches PREPARED. > Signed-off-by: Joonho Lee <[email protected]> [Severity: Low] This isn't a runtime bug, but the Fixes: trailer sits in the middle of the commit message rather than in the trailer block above Signed-off-by:, and the final paragraph states that ACK returns -EBADFD once the core reports XRUN whereas virtsnd_pcm_ack_state() returns -EPIPE for SNDRV_PCM_STATE_XRUN in this patch. > diff --git a/sound/virtio/virtio_pcm_ops.c b/sound/virtio/virtio_pcm_ops.c > index 1091100a4c982..983c6f83d1231 100644 > --- a/sound/virtio/virtio_pcm_ops.c > +++ b/sound/virtio/virtio_pcm_ops.c [ ... ] > @@ -461,41 +530,168 @@ virtsnd_pcm_cp_pointer(struct snd_pcm_substream > *substream) > > +/* The caller holds the PCM lock, also used by DROP and state transitions. */ > +static int virtsnd_pcm_ack_state(struct snd_pcm_substream *substream) > +{ > + switch (substream->runtime->state) { > + case SNDRV_PCM_STATE_XRUN: > + return -EPIPE; > + case SNDRV_PCM_STATE_PREPARED: > + case SNDRV_PCM_STATE_RUNNING: > + case SNDRV_PCM_STATE_PAUSED: > + case SNDRV_PCM_STATE_DRAINING: > + if (atomic_read(&substream->runtime->buffer_accessing) < 0) > + return -EBADFD; > + return 0; > + default: > + return -EBADFD; > + } > +} [ ... ] > +static int virtsnd_pcm_cp_ack(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); > + struct virtio_snd_queue *queue = virtsnd_pcm_queue(vss); > + struct virtsnd_pcm_transfer transfer = {}; > + int rc; > + > + rc = virtsnd_pcm_ack_state(substream); > + if (rc) > + return rc; > + > + scoped_guard(spinlock_irqsave, &queue->lock) { > + guard(spinlock)(&vss->lock); > + if (vss->preparing || !vss->prepared) > + return -EBADFD; > + /* Keep only the post-STOP capture tail available during drain. > */ > + if (vss->stopped && > + (vss->xfer_xrun || > + substream->runtime->state != SNDRV_PCM_STATE_DRAINING)) > + return -EBADFD; > + if (vss->xfer_xrun) { > + rc = -EPIPE; > + } else { > + transfer.indirect = vss->pcm_indirect; > + rc = snd_pcm_indirect_capture_transfer(substream, > + > &transfer.indirect, > + > virtsnd_pcm_trans_copy); > + if (!rc) > + rc = transfer.error; > + } > + if (rc) > + virtsnd_pcm_transfer_failed(vss); > + else > + vss->pcm_indirect = transfer.indirect; > + } > + if (rc) { > + dev_err(&vss->snd->vdev->dev, > + "SID %u: capture ACK transfer failed: %d\n", > + vss->sid, rc); > + return -EPIPE; > + } > + > + return 0; > +} > + > +/** > + * virtsnd_pcm_reset() - Reset PCM pointers and complete prepare admission. > + * @substream: Kernel ALSA substream. > + * > + * Context: PCM stream lock held. > + * Return: 0 on success, -errno on failure. > + */ > +static int virtsnd_pcm_reset(struct snd_pcm_substream *substream) > +{ > + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); > + int rc; > + > + rc = snd_pcm_lib_reset(substream); > + scoped_guard(spinlock_irqsave, &vss->lock) { > + if (vss->preparing) { > + vss->prepared = !rc; > + vss->preparing = false; > + } > + } > > - return snd_pcm_indirect_capture_transfer(substream, &vss->pcm_indirect, > - virtsnd_pcm_trans_copy); > + return rc; > } [Severity: Medium] Can virtsnd_pcm_reset() reopen ACK admission on a substream before snd_pcm_post_prepare() transitions the group to SNDRV_PCM_STATE_PREPARED? CPU0 CPU1 snd_pcm_prepare(s0) snd_pcm_action_nonatomic(...) snd_pcm_do_prepare(s1) virtsnd_pcm_sync_stop(s1) vss1->stopped = false virtsnd_pcm_prepare(s1) snd_pcm_reset_substream(s1, ...) virtsnd_pcm_reset(s1) vss1->prepared = true vss1->preparing = false snd_pcm_do_prepare(s2) ... (sleeps or fails) snd_pcm_sync_ptr(s1) pcm_lib_apply_appl_ptr(s1, ...) virtsnd_pcm_pb_ack(s1) / virtsnd_pcm_cp_ack(s1) <-- accepted before post_prepare In snd_pcm_action_group(), snd_pcm_do_prepare() runs sequentially on each linked member before snd_pcm_post_prepare() runs on any of them, and snd_pcm_action_nonatomic() only sets runtime->buffer_accessing to -1 on the ioctl target substream (and snd_pcm_sync_ptr() does not check buffer_accessing at all). If a linked member s1 entered prepare from PREPARED, PAUSED, or capture DRAINING, virtsnd_pcm_reset(s1) sets vss1->prepared = true and vss1->preparing = false and releases s1's PCM stream lock before s2 completes snd_pcm_do_prepare(s2). While s2 sleeps in snd_pcm_do_prepare(s2) (or permanently if s2 fails prepare, since snd_pcm_action_prepare has no undo_action), playback ACKs on s1 queue new TX buffers to the virtqueue before prepare completes. In addition, because virtsnd_pcm_cp_ack() only checks runtime->state != SNDRV_PCM_STATE_DRAINING when vss->stopped is true, a capture substream re-prepared from DRAINING has vss1->stopped == false after virtsnd_pcm_sync_stop(s1) and accepts capture ACKs while runtime->state is still DRAINING, driving vss1->pcm_indirect.sw_ready negative. -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=4
