musings on session service mgmt

[Colin Walters]

On Fri, 2008-01-04 at 12:12 -0500, David Zeuthen wrote:
> On Fri, 2008-01-04 at 12:04 -0500, Colin Walters wrote:
> > Sending SIGHUP to all processes manually is fine; in theory actually the
> > kernel will do this for you when the process session group leader exits.
> > Now, whether something is correctly set as the process group leader in
> > the twisted desktop login stack is an open question.  A regression here
> > would mostly be masked by the fact that *almost* everything run from the
> > desktop does connect to X11.
> 
> Lots of programs (including GNOME ones) daemonizes e.g. creates their
> own process group etc. etc. so clearly we can't rely on this. 

There's no reason for programs to daemonize for the desktop session.  If
they are, it's a bug.  Most likely it's just a case of someone thinking
their program is l33t because it's a "daemon".

> That's why we need to iterate over the process list and send SIGHUP to
> processes matching the uid and XDG_SESSION_COOKIE (or other attribute
> but XDG_SESSION_COOKIE is what we have right now). It's not really
> rocket science.

It's also working around bugs in other apps; and I don't think the list
of buggy apps is very large.  GConf and bonobo are the two main
offenders.

> You are being vague here; I think you just use that term because Havoc
> said something vague about a babysitter execing stuff. The way I read
> this (it's vague so I'm guessing) sounds like it needs source code
> modification and if it isn't clear I don't think that's an option.

It doesn't require modifying apps.  The idea is just to have a binary
which monitors X11/DBus, and can fork()/exec() a child binary to
monitor.  If X11 goes away, it kills the child.  Thus the only thing
that needs to be modified is that the session startup script is changed
from:

some-random-daemon --args

to:

dbus-scope-to-session some-random-daemon --args

> > But I think (generally speaking) most
> > projects nowadays *should* gain a dbus dep, and if we can explain
> > clearly to them why it it useful, they would accept it.
> 
> I think that is what they call wishful thinking. Seriously.

Let's be more concrete here - what other apps are buggy?