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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jul 29, 2016 at 02:23:20PM +0100, Andrew Cooper wrote:
> On 29/07/16 14:12, Wei Liu wrote:
> > On Fri, Jul 29, 2016 at 02:06:56PM +0100, Andrew Cooper wrote:
> >> On 29/07/16 13:58, Wei Liu wrote:
> >>> On Fri, Jul 29, 2016 at 01:43:42PM +0100, Andrew Cooper wrote:
> >>>> On 29/07/16 13:07, Wei Liu wrote:
> >>>>> There were two synchronisation issues for the old code:
> >>>>>
> >>>>> 1. There was no guarantee that guest console was ready before "xl
> >>>>>    console" invocation.
> >>>>> 2. There was no guarantee that runner wouldn't not exit before all test
> >>> s/not//
> >>>
> >>>>>    guests were gone.
> >>>> Sorry, but I can't parse this.
> >>>>
> >>>> The runner existing before xl has torn down the guest is very
> >>>> deliberate, because some part of hvm guests is terribly slow to tear
> >>>> down; waiting synchronously for teardown tripled the wallclock time to
> >>>> run a load of tests back-to-back.
> >>>>
> >>> Then you won't know if a guest is leaked or it is being slowly destroyed
> >>> when a dead guest shows up in the snapshot of 'xl list'.
> >>>
> >>> Also consider that would make back-to-back tests that happen to have a
> >>> guest that has the same name as the one in previous test fail.
> >> test names are globally unique, so this isn't an issue.
> >>
> >> Also, the wait for `xl console` to complete shows that @releasedomain
> >> has been fired for the domain.
> >>
> > Are you suggesting waiting for "xl console" only is good enough?
> 
> The "stdout, _ = console.communicate()" line waits for `xl console` to
> exit.  (In fact, `xl` exec()'s `xenconosle`)
> 
> As we never put a CTRL-] into stdin, `xl console` only exits when the
> PTY shuts, which is when xenconsoled decided the domain has terminated.
> 
> So, yes - I think this is safe.
> 

TBH I would rather to be explicit in this regard. I would rather stick
with checking "xl create".

Wei.

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