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

[Paolo Bonzini]

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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.

Paolo
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