Re: [libvirt] [PATCH] Add migration APIs for libxl driver
On 03/16/2012 11:53 AM, Jim Fehlig wrote:
Question for other libvirt devs:
Many of the libxl driver functions use this pattern
- lock driver
- vm = virDomainFindByUUID // acquires dom obj lock
- unlock driver
- do stuff
- virDomainObjUnlock
In some cases, "do stuff" requires obtaining the driver lock (e.g.
removing a domain from driver's domain list), in which case there is
potential for deadlock. Any suggestions for preventing the deadlock
*and* avoiding locking the driver during long running operations?
See src/qemu/THREADS.txt. That gives the details on how to drop the
driver lock and even the domain object lock, by maintaining a reference
count and job condition on each domain to ensure that others can still
use the driver, just not for the domain whose job is still occupied.
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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