[alsa-devel] [PATCH - JACK IO plug 1/2] jack: Avoid call to snd_pcm_avail_update() from JACK thread

[Takashi Iwai]

On Tue, 03 Jul 2018 13:58:06 +0200,
<twischer at de.adit-jv.com> wrote:
> 
> From: Timo Wischer <twischer at de.adit-jv.com>
> 
> snd_pcm_avail_update() can call snd_pcm_jack_stop() but
> snd_pcm_jack_stop() should not be called by the JACK thread.
> It should only be called by the thread how has called
> snd_pcm_jack_start().
> 
> In addition the execution of snd_pcm_avail_update() can take a while.
> Therefore it should not be called by the JACK thread to not block this
> thread.
> 
> Signed-off-by: Timo Wischer <twischer at de.adit-jv.com>

With that change, avail cannot be a negative, as
snd_pcm_ioplug_avail() returns snd_pcm_uframes_t.
A couple of checks are redundant and confuse readers as if it's still
a signed value.


Takashi


> 
> diff --git a/jack/pcm_jack.c b/jack/pcm_jack.c
> index e3df4d2..b643d93 100644
> --- a/jack/pcm_jack.c
> +++ b/jack/pcm_jack.c
> @@ -67,7 +67,7 @@ static int pcm_poll_block_check(snd_pcm_ioplug_t *io)
>  
>  	if (io->state == SND_PCM_STATE_RUNNING ||
>  	    (io->state == SND_PCM_STATE_PREPARED && io->stream == SND_PCM_STREAM_CAPTURE)) {
> -		avail = snd_pcm_avail_update(io->pcm);
> +		avail = snd_pcm_ioplug_avail(io, jack->hw_ptr, io->appl_ptr);
>  		if (avail >= 0 && avail < jack->min_avail) {
>  			while (read(io->poll_fd, &buf, sizeof(buf)) == sizeof(buf))
>  				;
> @@ -84,7 +84,7 @@ static int pcm_poll_unblock_check(snd_pcm_ioplug_t *io)
>  	snd_pcm_sframes_t avail;
>  	snd_pcm_jack_t *jack = io->private_data;
>  
> -	avail = snd_pcm_avail_update(io->pcm);
> +	avail = snd_pcm_ioplug_avail(io, jack->hw_ptr, io->appl_ptr);
>  	if (avail < 0 || avail >= jack->min_avail) {
>  		write(jack->fd, &buf, 1);
>  		return 1;
> -- 
> 2.7.4
>