[alsa-devel] "Resource temporarily unavailable" while reading although poll returns POLLIN event

Jaroslav Kysela perex at perex.cz
Wed Apr 21 19:18:29 CEST 2010

On Wed, 21 Apr 2010, Stefan Schoenleitner wrote:

> Stefan Schoenleitner wrote:
>> Since a POLLIN event only occurs after at least a full period is available for
>> reading (as set up by snd_pcm_sw_params_set_avail_min() above)
>> and I only read after a POLLIN event occured on the capture device fd,
>> I really do not understand why I get the above error.
> By using snd_pcm_avail_update() I found out that polling on the PCMs
> *does not work at all*.
> Although I verified that avail_min is 160 frames, polling on the
> capture/playback PCMs returns a POLLIN/POLLOUT event even if the number
> of frames for reading/writing *is less than avail_main*.
> I also tried snd_pcm_wait() which should also wait until there are at
> least avail_min frames available for reading/writing.
> The result is the same: snd_pcm_avail_update() shows that it returns
> even if there are far less than avail_min frames available for processing.
> I suspect that this is a bug in ALSA ?

It might be. Could you post snd_pcm_dump() when you read less frames?


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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