[systemd-devel] [PATCH 2/2] domain: grab the domain's parent lock only when needed

[Djalal Harouni]

On Sat, Mar 22, 2014 at 08:28:38PM +0100, Kay Sievers wrote:
> On Sat, Mar 22, 2014 at 7:56 PM, Djalal Harouni <tixxdz at opendz.org> wrote:
> > On Sat, Mar 22, 2014 at 07:37:38PM +0100, Kay Sievers wrote:
> >> On Sat, Mar 22, 2014 at 3:43 PM, Daniel Mack <daniel at zonque.org> wrote:
> >> >> Also it seems that now there is only support for one level of nested
> >> >> domains? will this be increased?
> >> >
> >> > I don't think so. What's your use case here?
> >>
> >> We never tried, but the code was supposed to allow stacking of them.
> >> I'll fix it.
> > Yes I was thinking of applications that create domains, they wont work
> > if they are inside a container domain!
> 
> Domain creation at the moment is limited to privileged processes,
Yes!

> because we have no limits for accounting or other safeguards in place.
> Domains are a conceptually bit closer to an OS container, applications
> should see a custom endpoint or can create their own private buses in
> the domain they run in.
Ok, thanks for the explanation.

> >> >> 2) What about creating custom endpoints on the bus that was already
> >> >> unrefed ? IMHO this is the same scenario!
> >> >
> >> > That shouldn't happen of course. We've been dealing with locking in that
> >> > area quite a bit, but we might have overlooked something. Please send a
> >> > patch if you see such an unsafe locking scenario.
> >> >
> >> >> Hmm perhaps this can be improved by taking a ref ASAP and revalidate
> >> >> objects by checking the "*->disconnected" ?
> >> >
> >> > ->disconnected isn't so much of an issue, and we do check for it where
> >> > necessary. Apart from that, users that store a pointer to any object
> >> > should take a reference, so it can't disappear underneath them. But
> >> > again, if you think we've overlooked anything, let us know. Reviewing
> >> > all these details is certainly much appreciated.
> >>
> >> I'll add a few more "disconnected checks" before we link into the
> >> parent objects.
> > Yes, I've located some sites, and I'm trying to do more tests...
> >
> > I'll get back to you, Thanks Daniel, Kay!
> 
> I've committed a few more guards which check for disconnected, right
> before we try to link into the parent object.
Yep, I see it now, commit e7f6ec74d3f that was fast ;-)

Thanks

-- 
Djalal Harouni
http://opendz.org