Re: [Qemu-devel] migration: qemu-coroutine-lock.c:141: qemu_co_mutex_unlock: Assertion `mutex->locked == 1' failed

[Alexey Kardashevskiy]

On 09/17/2014 07:25 PM, Paolo Bonzini wrote:
> Il 17/09/2014 11:06, Stefan Hajnoczi ha scritto:
>> I think the fundamental problem here is that the mirror block job 
>> on the source host does not synchronize with live migration.
> 
>> Remember the mirror block job iterates on the dirty bitmap
>> whenever it feels like.
> 
>> There is no guarantee that the mirror block job has quiesced before
>> migration handover takes place, right?
> 
> Libvirt does that.  Migration is started only once storage mirroring
> is out of the bulk phase, and the handover looks like:
> 
> 1) migration completes
> 
> 2) because the source VM is stopped, the disk has quiesced on the source
> 
> 3) libvirt sends block-job-complete
> 
> 4) libvirt receives BLOCK_JOB_COMPLETED.  The disk has now quiesced on
> the destination as well.
> 
> 5) the VM is started on the destination
> 
> 6) the NBD server is stopped on the destination and the source VM is quit.
> 
> It is actually a feature that storage migration is completed
> asynchronously with respect to RAM migration.  The problem is that
> qcow2_invalidate_cache happens between (3) and (5), and it doesn't
> like the concurrent I/O received by the NBD server.

How can it happen at all? I thought there are 2 channels/sockets - one for
live migration, one for NBD and they concur, nope?

btw any better idea of a hack to try? Testers are pushing me - they want to
upgrade the broken setup and I am blocking them :) Thanks!


-- 
Alexey