Why VM gets crashed in the post-copy phase during live migration

Issue

• During live migration, VM gets crashed with below error in the vdsm logs.

2019-03-27 14:15:04,683+0100 INFO  (libvirt/events) [virt.vm] (vmId='11111111-1111-1111-1111-11111111') Migration switched to post-copy mode (vm:5651)

2019-03-27 14:15:34,692+0100 ERROR (vm/7ee242b8) [virt.vm] (vmId='11111111-1111-1111-1111-11111111') The vm start process failed (vm:949)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 893, in _startUnderlyingVm
    self._completeIncomingMigration()
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 4162, in _completeIncomingMigration
    self._attachLibvirtDomainAfterMigration(finished, timeout)
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 4227, in _attachLibvirtDomainAfterMigration
    self._sync_metadata()
  File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 5253, in _sync_metadata
    self._md_desc.dump(self._dom)
  File "/usr/lib/python2.7/site-packages/vdsm/virt/metadata.py", line 514, in dump
    0)
  File "/usr/lib/python2.7/site-packages/vdsm/virt/virdomain.py", line 106, in f
    raise toe
TimeoutError: Timed out during operation: cannot acquire state change lock (held by monitor=remoteDispatchDomainMigratePrepare3Params)