Re: [gdm-list] [PATCH] fix race condition when setting the model for the face browser

[Ludwig Nussel <ludwig nussel suse de>]

Brian Cameron wrote:
> Ludwig:
> >> Could you explain in more detail how the messages pass back and
> >> forth to support the Face Browser?
> > 
> > Well, you are the maintainer of GDM. Don't ask me how or why it
> > works the way it works :-)
> 
> This section of the code was written by the previous maintainer,
> so I'm probably not that much more familiar with it than you.  I
> do know that GDM supports a few different mechanisms for communicating
> between the client and server (e.g. FIFO, SUP, and SOP protocols
> as mentioned in the daemon/gdm.h file).  Perhaps GDM already has
> another protocol mechanism that would be more appropriate for
> passing the face browser data?

No idea.

> >> Could we think of a different way to make this work that would
> >> avoid the problem?  Is there really a need for the GUI to talk to
> >> the daemon to display the Face Browser?
> > 
> > That's what I am wondering too.
> > 
> >> Why can't the daemon just set up some data in a directory like
> >> /var/tmp/gdm/facebrowser so that when the GUI starts up it can
> >> just read some configuration files there (and image files) and set
> >> itself up properly without having to talk to the daemon at all?
> > 
> > You'd have to maintain that cache directory somehow so that if a
> > user changes the image the cache gets udpated as well. 
> 
> This isn't really that much more than what GDM already does.  It
> already regrabs the image from the user's $HOME directory every
> time a GUI is displayed.  Is re-updating a cache every time the
> GUI is displayed any worse?

*shrug*

> > That's
> > overkill for little gain. IMHO custom images are just a gimmick for
> > home users which means low number of users and local home
> > directories. So the most simple way to read the images is to just
> > access the file in the home directory directly as user gdm. If gdm
> > is not allowed to access the file then so it be.
> 
> The problem with making this sort of change is that GDM may seem to
> break for users if we change this behavior.  You will have to talk
> me into making a change that will generate a log of bug reports
> asking why things stopped working.  Can't we think of a way to fix
> this that would be less likely to break current behavior?
> 
> Also there may be reasons we're not thinking about why it makes
> sense for the daemon to poke for these image files rather than the
> GDM user.  I've reviewed the GDM ChangeLog and docs, but don't see
> any real explination why it works this way.  Thoughts?

Well, it allows gdm to display files the gdm user is not permitted
to read. That's the only reason I can think of why you need to be
root for that job. Maybe some distro has rather restrictive
permissons on ~ by default?

cu
Ludwig

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