[alsa-devel] [PATCH] ASoC: rsnd: stop all working stream when .remove

[Kuninori Morimoto]

Hi Takashi

This is reply for old email.
This thread talked about hot-unplug during playback.

	aplay xxx &
	echo xxx > /sys/bus/platform/drivers/xxx/unbind

We need to stop all components on framework level.
And you kindly created its prototype solution.

> ---
> diff --git a/include/sound/core.h b/include/sound/core.h
> index 4104a9d1001f..5f181b875c2f 100644
> --- a/include/sound/core.h
> +++ b/include/sound/core.h
> @@ -133,6 +133,7 @@ struct snd_card {
>  	struct device card_dev;		/* cardX object for sysfs */
>  	const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
>  	bool registered;		/* card_dev is registered? */
> +	wait_queue_head_t remove_sleep;
>  
>  #ifdef CONFIG_PM
>  	unsigned int power_state;	/* power state */
> @@ -240,6 +241,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
>  		 struct snd_card **card_ret);
>  
>  int snd_card_disconnect(struct snd_card *card);
> +void snd_card_disconnect_sync(struct snd_card *card);
>  int snd_card_free(struct snd_card *card);
>  int snd_card_free_when_closed(struct snd_card *card);
>  void snd_card_set_id(struct snd_card *card, const char *id);
> diff --git a/sound/core/init.c b/sound/core/init.c
> index 32ebe2f6bc59..5cde6cc0d867 100644
> --- a/sound/core/init.c
> +++ b/sound/core/init.c
> @@ -255,6 +255,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
>  #ifdef CONFIG_PM
>  	init_waitqueue_head(&card->power_sleep);
>  #endif
> +	init_waitqueue_head(&card->remove_sleep);
>  
>  	device_initialize(&card->card_dev);
>  	card->card_dev.parent = parent;
> @@ -452,6 +453,17 @@ int snd_card_disconnect(struct snd_card *card)
>  }
>  EXPORT_SYMBOL(snd_card_disconnect);
>  
> +void snd_card_disconnect_sync(struct snd_card *card)
> +{
> +	snd_card_disconnect(card);
> +	spin_lock_irq(&card->files_lock);
> +	wait_event_lock_irq(card->remove_sleep,
> +			    list_empty(&card->files_list),
> +			    card->files_lock);
> +	spin_unlock_irq(&card->files_lock);
> +}
> +EXPORT_SYMBOL_GPL(snd_card_disconnect_sync);
> +
>  static int snd_card_do_free(struct snd_card *card)
>  {
>  #if IS_ENABLED(CONFIG_SND_MIXER_OSS)
> @@ -957,6 +969,8 @@ int snd_card_file_remove(struct snd_card *card, struct file *file)
>  			break;
>  		}
>  	}
> +	if (list_empty(&card->files_list))
> +		wake_up_all(&card->remove_sleep);
>  	spin_unlock(&card->files_lock);
>  	if (!found) {
>  		dev_err(card->dev, "card file remove problem (%p)\n", file);


I tried this patch, and noticed 2 issues (at this point).
I think below thing happen on this process.

 1) snd_pcm_dev_disconnect() is called
  - status will be SNDRV_PCM_STATE_DISCONNECTED;

 2) snd_pcm_release() is called
  - snd_pcm_release_substream() is called
   - snd_pcm_drop() is called

snd_pcm_drop() will call snd_pcm_stop(), and
it stops each driver. This is needed.
The issue will be happen if 1) happen before 2) (I think)

1st issue is

snd_pcm_drop() has this check

	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
		return -EBADFD;

if 1) happen before 2), snd_pcm_drop() returns immediately,
and doesn't call snd_pcm_stop().

I modified this as quick-hack locally.
Then, 2nd issue happen on snd_pcm_stop(). it will call snd_pcm_do_stop(),
and it has

	if (substream->runtime->trigger_master == substream &&
	    snd_pcm_running(substream))
		substream->ops->trigger(substream, SNDRV_PCM_TRIGGER_STOP);

Here, trigger isn't called, because snd_pcm_running() is 0.
This is because status is SNDRV_PCM_STATE_DISCONNECTED if 1) happen before 2).

I don't know detail of these status magic,
but do you have some idea/solution ?

Best regards
---
Kuninori Morimoto