On Mon, May 11, 2009 at 12:47:38PM +0100, Mark McLoughlin wrote: > On Mon, 2009-05-11 at 12:11 +0100, Daniel P. Berrange wrote: > > Back in March I attempted to fix the event loop handling of deleted file > > handles > > > > http://www.redhat.com/archives/libvir-list/2009-March/msg00246.html > > > > but have merely succeeded in screwing it up in a different fun & exciting > > way. That patch fixed a case where there was a deleted file handle in the > > list at the time virEventRunOnce() starts. Which was nice. Not nice, though > > was that it then breaks the case where a file handle is deleted during the > > course of dispatching events afer poll(). Investigating this also identified > > that when we were marking a file handle as deleted, we were forgetting to > > run virEventInterrupt(), which meant that in some cases the main thread > > would not be woken up until the next event triggers. Not very critical, > > but at the same time, not good because it delays cleanup & release of > > resources. > > > > This series of patches fixes the problems, and more importantly, adds a > > unit test which cover these nasty edge cases. > > It's not obvious to me from your description, so for others, one of the > problems these patches fix is where destroying one running guest can > cause another to also be destroyed: > > https://bugzilla.redhat.com/499698 NB That's just one symptom. The core problem is that you end up with an off-by-1 error when dispatching the callbacks. ie, instead of dispatching the nth callback, we dispatch the nth+1 callbck. There are lots of different things registering callbacks so effects are pretty unpredictable. Normally the callbacks for running guests don't align, but if you restart libvirtd while a set of guests are running, you end up with all the guest callbacks registered in series, so are quite likely to see this double destroy. Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| -- Libvir-list mailing list Libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list