Re: [Xen-devel] Domains not being destroyed properly

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Fri, 2011-06-24 at 15:15 +0100, Anthony Wright wrote:
> On 24/06/2011 14:45, Ian Campbell wrote:
> > On Fri, 2011-06-24 at 13:54 +0100, Anthony Wright wrote:
> >> A reaper would have to maintain a list of domains as they were before the
> >> notification to compare against the list after the notification to be
> >> able to issue a notification for the domain that has died. If that list
> >> got out of sync it would start issuing incorrect domain death 
> >> notifications.
> > You don't need to maintain a list, simply call libxl_list_domain() and
> > for each returned domain examine the flags and shutdown reason to
> > determine if it is dead (and why), dying or still running.
> >
> > Since you are explicitly arranging that nothing else will destroy
> > domains once they die so they will always be in that list when you get
> > to them.
> My original thought on reaper was that it was only responsible for
> helping notify user space applications of a domain's death,  but you
> seem to be suggesting that it should also be responsible for tidying up
> after a domain death as well. Isn't some other part of the system
> already fulfilling this role?

It would be xl, but you are using xl create -e which explicitly turns
off that behaviour.

> It seems that for 'xl create' this tidy up is already being done, and I
> had presumed the code for 'xl create -e' tidy up already exists but
> wasn't working correctly.

No, "xl create -e" means "don't babysit this domain waiting for it to
die. I, the user, will take care of cleaning it up manually when it
dies".

You said you were using -e because you didn't want a load of processes
sitting around to fulfil this requirement and so I suggested you might
like a single reaper daemon which takes case of it instead.

Ian.


>  If you're saying the 'xl create -e' tidy up
> code needs to be written, that's probably beyond my knowledge of xen,
> and in any case I'm not sure it should be in reaper. Reaper should
> notify user space of any domain destruction whether created by 'xl
> create -e' or 'xl create'. If reaper did the tidy up for 'xl create -e'
> it would have access to information needed to pass to the user space
> applications, however for an 'xl create' domain death this information
> may no longer be available since 'xl create' may have already tidied up.



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