Re: [Xen-devel] [PATCH] Add timeout to xenconsole to fix race condition in xm create -c

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Christian Limpach wrote:

> On 8/30/05, Anthony Liguori <aliguori@xxxxxxxxxx> wrote:
>  
>
> > This should address the problems people are having now.
> >
> > Wait a little bit for tty to appear.  There is a race condition that
> > occurs after xend creates a domain.  Since no event triggers consoled to
> > re-examine existing domains, we'll often not see the new pty by the time
> > we're here.  Since consoled sleeps for 2 second periods, a 5 second
> > timeout should keep us covered.
> >    
> I've applied this with slighly changed comments since xenconsoled now
> uses watches and should setup the tty almost immediately.  The race
> still exists though.
>  
Yes, what we really want is a event-dispatch mechanism.  It's something 
we've talked about a bit here but without flushing out any sort of 
actual design.
> > A xenstore watch isn't much better since we don't want to block forever
> > if given an invalid domain or worse yes, a domain that someone else has
> > connected to.
> >    
> It would improve the responsiveness but a timeout is still needed for
> the reasons you pointed out.
>
> Finally, there's still an issue with storing the console tty
> information in /console/<domid> -- there might be stale data from a
> previous domain having the same domid and the client might run before
> the console daemon has rewritten the tty entry.  I think this is best
> fixed by moving the console tty information into the domain's /domain
> tree.
>  
Rusty had some objections to this originally--this is why its not there 
now.  Rusty?
Regards,

Anthony Liguori

>    christian
>
>  

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