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Re: [Qemu-devel] [PATCH 2/3] block: use BDRV_POLL_WHILE() in bdrv_rw_vms
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From: |
Kevin Wolf |
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Subject: |
Re: [Qemu-devel] [PATCH 2/3] block: use BDRV_POLL_WHILE() in bdrv_rw_vmstate() |
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Date: |
Thu, 18 May 2017 09:57:59 +0200 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 17.05.2017 um 22:16 hat Eric Blake geschrieben:
> On 05/17/2017 12:09 PM, Stefan Hajnoczi wrote:
> > Calling aio_poll() directly may have been fine previously, but this is
> > the future, man!
>
> lol
>
> > The difference between an aio_poll() loop and
> > BDRV_POLL_WHILE() is that BDRV_POLL_WHILE() releases the AioContext
> > around aio_poll().
> >
> > This allows the IOThread to run fd handlers or BHs to complete the
> > request. Failure to release the AioContext causes deadlocks.
> >
> > Using BDRV_POLL_WHILE() partially fixes a 'savevm' hang with -object
> > iothread.
>
> I'm surprised at how many separate hangs we actually had!
How hard would it be to write some test cases for this? Dataplane has
a serious lack of automated testing.
Kevin
pgpc_HtekDvfA.pgp
Description: PGP signature
[Qemu-devel] [PATCH 3/3] migration: avoid recursive AioContext locking in save_vmstate(), Stefan Hajnoczi, 2017/05/17
Re: [Qemu-devel] [PATCH 0/3] block: fix 'savevm' hang with -object iothread, Paolo Bonzini, 2017/05/17