Re: [Qemu-devel] Intel HDA and ALSA audio driver hogging event loop

[Stefan Hajnoczi]

On Thu, Oct 20, 2016 at 10:08 AM, P J P <address@hidden> wrote:
>   Hello Gerd,
>
> +-- On Thu, 20 Oct 2016, Stefan Hajnoczi wrote --+
> | A RHEL 7.2 guest sometimes hangs when I play back a wav file on the
> | Intel HDA emulated sound card using the QEMU ALSA audio driver.
> |
> | intel_hda_xfer() transfers samples between the emulated card and the
> | QEMU audio subsystem.  The following case causes a problem:
> |     if (st->ctl & (1 << 26)) {
> |         /*
> |          * Wait with the next DMA xfer until the guest
> |          * has acked the buffer completion interrupt
> |          */
> |         return false;
> |     }
> |
> | If the guest hasn't acked the interrupt yet then Intel HDA returns
> | without providing any samples.  The QEMU ALSA driver keeps monitoring
> | the file descriptor so the next event loop iteration will try to
> | transfer samples again.
>
> I was looking at another loop issue in 'intel_hda_xfer'
>   -> https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg04682.html
>
> It does not address the above case, but maybe both could be fixed together.

These two issues are unrelated but I've reviewed your patch.

Stefan