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Re: [Qemu-devel] Intel HDA and ALSA audio driver hogging event loop
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] Intel HDA and ALSA audio driver hogging event loop |
Date: |
Thu, 20 Oct 2016 10:38:02 +0100 |
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