Re: [Xen-devel] [XTF PATCH] xtf-runner: fix two synchronisation issues

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Wei Liu writes ("Re: [XTF PATCH] xtf-runner: fix two synchronisation issues"):
> On Fri, Jul 29, 2016 at 03:21:52PM +0100, Ian Jackson wrote:
> > Wei Liu writes ("[XTF PATCH] xtf-runner: fix two synchronisation issues"):
> > > There were two synchronisation issues for the old code:
> > > 
> > > 1. There was no guarantee that guest console was ready before "xl
> > >    console" invocation.
> > 
> > Is this not a bug in xl console ?
> 
> I don't think so. It gives up when it can't get tty from xenstore. I
> think that's reasonable.

If you say
  xl create /etc/xen/foo.cfg
  xl console foo
then surely you shouldn't find that xl console fails because of some
race.

> > > 2. Poll xenstore guest console node to make sure console is available
> > >    before "xl console" invocation.
> > 
> > Users of things like xl shouldn't need to prat about in xenstore too.
> 
> What does this mean?

I mean that xenstore is part of the implementation of libxl, not part
of its public interface.  In this sense it is a bit like libxc.
libxl callers should (in general) not look at xenstore - and of
course they should therefore;2~ not need to do so.

If the xtf runner needs to look in xenstore (other than perhaps if
it's doing strange things there as part of its test cases) then that
means there is some interface or capability missing in libxl.

OTOH I'm slightly confused because I was under the impression that
there was a polling loop in xl console (xenconsole) already.

Maybe I don't understand your problem.

Ian.

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