Re: Locking

[Julian King <jpk28 cus cam ac uk>]

> Indeed, as Michael says. If you have two gconfd processes, everything
> breaks.

Good, that means we did at least come close to understanding the
code.

Of all the locking code we've tried to fix this was probably the most
complex, but also probably the only one which wasn't terminally broken
anyway (If you are interested X has two bits of locking using hard links
and neither of them work, nfs or otherwise).

> If you are willing to limit each user's logins to one computer, a
> really simple solution is to move the lock to /tmp or /var which is
> normally a standard, local filesystem.

This would be sub-optimal in that we do have servers which people could
in principle access X applications from at the same time as the 
workstations, but may well be a tolerable work around.

> > a) Select at compile time
> > b) Select at run time via a configuration option
> > c) Select at run time via a command line option
> > d) (b) and (c) both options
> > e) Something else I've not thought of.
> 
> I think a) would generally be right, but b) sounds fine too. The way
> gconfd gets run c) doesn't really work out. e) might be good, who
> knows. ;-)

I think we would prefer (b) - because then RedHat (whose rpms we are
using) will pick up the changes and make our life easier - however 
before any of this is relevant we would need a fix which works.  :-)

(Ooh, was just about to send the mail when I noticed your Email address... :-)

> So the simple start is a --with-per-machine-lock configure option; if
> you can come up with a in-the-users-home-dir locking scheme that
> works, I'd be impressed (I have no idea how to do this without getting
> stale locks fairly often).

I'm not going to attempt to explain the details of what I think your
locking mechanism does here until I've had far more caffeine, however
I believe that we have the primitives available to us to make a 
functionally equivalent mechanism which works.  It is just that we
don't have Unix-style locks or hard links - we do, in theory have
mandatory locking, so we will see.

Cheers for the input guys.

One last question, if we do actually come up with a patch, where should
we send it, here to this list or somewhere else?

> Havoc

Julian