Re: [PATCH] ALSA: pcm: update state after xrun

[Takashi Iwai <tiwai@suse.de>]

On Tue, 27 Oct 2026 14:12:33 +0100,
Mikael Magnusson wrote:
> 
> If the snd_pcm_update_hw_ptr call from snd_pcm_status is what triggers
> the xrun state (eg, as opposed to an IRQ), the returned status->state
> was stale and told userspace the device was still playing, so they could
> get confused about device state and hang indefinitely.
> 
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=222201
> Signed-off-by: Mikael Magnusson <mikachu@gmail.com>
> ---
>  sound/core/pcm_native.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 35152fae74..62a2bea043 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -1132,6 +1132,9 @@ int snd_pcm_status64(struct snd_pcm_substream *substream,
>  	status->trigger_tstamp_nsec = runtime->trigger_tstamp.tv_nsec;
>  	if (snd_pcm_running(substream)) {
>  		snd_pcm_update_hw_ptr(substream);
> +		/* update_hw_ptr may have put us in xrun state, update state */
> +		status->state = runtime->state;
> +		status->suspended_state = runtime->suspended_state;
>  		if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
>  			status->tstamp_sec = runtime->status->tstamp.tv_sec;
>  			status->tstamp_nsec =
> 

Thanks for the patch.  I can take this as-is, but what Sashiko
suggested in the review is also valid -- we may copy trigge_tstamp_*,
too.

Also, we don't have to always overwrite the values.  As a further
optimization, check the return value from snd_pcm_update_hw_ptr(), and
update only if it returns a negative (-EPIPE).

So, in the end, it'll be something like below.
Could you check whether this works for you?


thanks,

Takashi

-- 8< --
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -1131,7 +1131,13 @@ int snd_pcm_status64(struct snd_pcm_substream *substream,
 	status->trigger_tstamp_sec = runtime->trigger_tstamp.tv_sec;
 	status->trigger_tstamp_nsec = runtime->trigger_tstamp.tv_nsec;
 	if (snd_pcm_running(substream)) {
-		snd_pcm_update_hw_ptr(substream);
+		if (snd_pcm_update_hw_ptr(substream) < 0) {
+			/* update_hw_ptr may have put us in xrun state, update state */
+			status->state = runtime->state;
+			status->suspended_state = runtime->suspended_state;
+			status->trigger_tstamp_sec = runtime->trigger_tstamp.tv_sec;
+			status->trigger_tstamp_nsec = runtime->trigger_tstamp.tv_nsec;
+		}
 		if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
 			status->tstamp_sec = runtime->status->tstamp.tv_sec;
 			status->tstamp_nsec =