Re: [Qemu-devel] [PATCH] migration: fix crash in when incoming client channel setup fails

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jun 19, 2018 at 04:58:59PM +0100, Daniel P. Berrangé wrote:
> On Tue, Jun 19, 2018 at 04:45:05PM +0100, Dr. David Alan Gilbert wrote:
> > * Daniel P. Berrangé (berrange@redhat.com) wrote:
> > > The way we determine if we can start the incoming migration was
> > > changed to use migration_has_all_channels() in:
> > > 
> > >   commit 428d89084c709e568f9cd301c2f6416a54c53d6d
> > >   Author: Juan Quintela <quintela@redhat.com>
> > >   Date:   Mon Jul 24 13:06:25 2017 +0200
> > > 
> > >     migration: Create migration_has_all_channels
> > > 
> > > This method in turn calls multifd_recv_all_channels_created()
> > > which is hardcoded to always return 'true' when multifd is
> > > not in use.
> > > 
> > > This means that if channel initialization fails with normal
> > > migration, it'll never notice and attempt to start the
> > > incoming migration regardless.
> > 
> > I'm not sure if that was actually the cause, because older versions
> > had no check at all in socket_accept_incoming_migration.
> 
> Hmm, actually your write - it was a complicated series of refactorings
> for multifd, and I think I mis-identified. I'll do a proper bisect so
> we can have an accurate record.

Ok, this commit above introduces the latent bug, and then it is
activated by

  commit 36c2f8be2c4eb0003ac77a14910842b7ddd7337e
  Author: Juan Quintela <quintela@redhat.com>
  Date:   Wed Mar 7 08:40:52 2018 +0100

    migration: Delay start of migration main routines
    

Regards,
Daniel
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