[alsa-devel] Timer instability

[Lennart Poettering]

On Fri, 20.02.09 02:22, Lennart Poettering (mznyfn at 0pointer.de) wrote:

> > > 
> > > If necessary I could extract a test case for this, but my hope that
> > > you guys might have an idea what goes on without a test case, given
> > > that this smells so "overflowy" ;-)
> > > 
> > > And of course, how come ALSA triggers POLLIN if I asked it not to?
> > 
> > Are you using *_period_event() stuff?
> 
> Yes, I am. But ignore that part for now. I have now commented the use
> of that call. Now I certainly get more POLLOUTs as expected, but the
> real problem stays: after a few minutes _avail() will suddenly jump
> from next to zero to more then the hwbuf size in less than 1ms without
> any further inteference and with a buffer size of 350ms! There is
> something really wrong with the behaviour of _avail().
> 
> I can reproduce this only on ens1371 for now.

Actually it is worse than just the issue mentioned above. I also can
reproduce that _avail() tells me the device is almost completely full
(i.e. 370ms of data), and when i then go to sleep for 350ms then
afterwards _avail() will tell me that about 700ms are missing. From
the context the first _avail() was just wrong.

In summary: _avail() is completely unreliable on ens1371. It sometimes
returns values that are too high by once the buffer size, and
sometimes too low by once the buffer size.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
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