Thank you for your contribution! Sashiko AI review found 2 potential issues to consider: - [Medium] ALSA: pcm: spurious MSTOP timer notification in snd_pcm_complete_prepare() - [Medium] ALSA: pcm: race window between snd_pcm_post_prepare() and prepare_complete() --
commit 8b0a0bce1c3b8b4ee1000c353fc111291e35293e Author: Joonho Lee <[email protected]> ALSA: pcm: notify drivers after linked prepare completes This commit adds an optional prepare_complete callback to struct snd_pcm_ops and invokes it under the PCM stream lock after single or linked prepare actions complete or fail. > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c > index e4c2fe70fa705..40ac7fb614567 100644 > --- a/sound/core/pcm_native.c > +++ b/sound/core/pcm_native.c [ ... ] > @@ -1350,6 +1352,13 @@ static int snd_pcm_action_group(const struct > action_ops *ops, > ops->undo_action(s1, state); > } > } > + if (ops->complete_action) { > + snd_pcm_group_for_each_entry(s1, substream) { > + ops->complete_action(s1, state, false); > + if (s1 == s) > + break; > + } > + } > s = NULL; /* unlock all */ > goto _unlock; > } > @@ -1357,6 +1366,10 @@ static int snd_pcm_action_group(const struct > action_ops *ops, > snd_pcm_group_for_each_entry(s, substream) { > ops->post_action(s, state); > } > + if (ops->complete_action) { > + snd_pcm_group_for_each_entry(s, substream) > + ops->complete_action(s, state, true); > + } [Severity: Medium] Can another caller observe SNDRV_PCM_STATE_PREPARED and invoke ops->ack() or ops->trigger() in the unlocked window between snd_pcm_post_prepare() and snd_pcm_complete_prepare()? snd_pcm_post_prepare() calls snd_pcm_set_state(), which acquires pcm_stream_lock_irq(substream), publishes SNDRV_PCM_STATE_PREPARED, and unlocks before snd_pcm_complete_prepare() re-acquires the stream lock to call ops->prepare_complete(). CPU0 CPU1 snd_pcm_prepare() ... snd_pcm_post_prepare(s) snd_pcm_set_state(s, PREPARED) lock(s) __snd_pcm_set_state(s, PREPARED) unlock(s) snd_pcm_common_ioctl() snd_pcm_sync_ptr(s) lock(s) pcm_lib_apply_appl_ptr(s) s->ops->ack(s) <-- rejected snd_pcm_complete_prepare(s, true) lock(s) s->ops->prepare_complete(s, true) unlock(s) Because the driver still has admission closed until prepare_complete() runs, concurrent SNDRV_PCM_IOCTL_SYNC_PTR or SNDRV_PCM_IOCTL_START calls seeing SNDRV_PCM_STATE_PREPARED can fail with -EBADFD. In addition, if a concurrent snd_pcm_drop(), snd_pcm_drain(), or snd_pcm_suspend_all() changes runtime->state during the unlocked window, snd_pcm_complete_prepare() still calls prepare_complete(substream, true) on success, or overwrites SNDRV_PCM_STATE_SUSPENDED with SNDRV_PCM_STATE_SETUP on failure. [ ... ] > @@ -2099,10 +2118,29 @@ static void snd_pcm_post_prepare(struct > snd_pcm_substream *substream, > snd_pcm_set_state(substream, SNDRV_PCM_STATE_PREPARED); > } > > +static void snd_pcm_complete_prepare(struct snd_pcm_substream *substream, > + snd_pcm_state_t state, bool success) > +{ > + if (!substream->ops->prepare_complete) > + return; > + > + guard(pcm_stream_lock_irq)(substream); > + if (!success && substream->runtime->state != > SNDRV_PCM_STATE_DISCONNECTED) { > + if (substream->runtime->state != SNDRV_PCM_STATE_SETUP) { > + __snd_pcm_set_state(substream->runtime, > SNDRV_PCM_STATE_SETUP); > + snd_pcm_timer_notify(substream, > SNDRV_TIMER_EVENT_MSTOP); > + } [Severity: Medium] Does snd_pcm_complete_prepare() emit a spurious SNDRV_TIMER_EVENT_MSTOP notification when prepare fails? In snd_pcm_prepare(), PAUSED and SUSPENDED streams are already stopped via snd_pcm_stop() before snd_pcm_action_prepare runs, and snd_pcm_pre_prepare() rejects RUNNING and playback DRAINING streams with -EBUSY. Any substream reaching this path with runtime->state != SNDRV_PCM_STATE_SETUP (such as a re-prepare from PREPARED, XRUN, or capture DRAINING) does not have an active master timer, so calling snd_pcm_timer_notify(substream, SNDRV_TIMER_EVENT_MSTOP) delivers a master-stop event with a zero or stale runtime->trigger_tstamp to attached slave timers. -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=4
