Re: [PATCH] migration: Read state once

[Peter Xu <peterx@redhat.com>]

On Wed, Apr 13, 2022 at 12:33:29PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> The 'status' field for the migration is updated normally using
> an atomic operation from the migration thread.
> Most readers of it aren't that careful, and in most cases it doesn't
> matter.
> 
> In query_migrate->fill_source_migration_info the 'state'
> is read twice; the first time to decide which state fields to fill in,
> and then secondly to copy the state to the status field; that can end up
> with a status that's inconsistent; e.g. setting up the fields
> for 'setup' and then having an 'active' status.  In that case
> libvirt gets upset by the lack of ram info.
> The symptom is:
>    libvirt.libvirtError: internal error: migration was active, but no RAM info was set
> 
> Read the state exactly once in fill_source_migration_info.
> 
> This is a possible fix for:
> https://bugzilla.redhat.com/show_bug.cgi?id=2074205
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu