[BProc] bproc+autofs: oz_pgrp problem

[Erik Arjan Hendriks]

On Thu, May 09, 2002 at 12:22:15PM +0200, hanzl at noel.feld.cvut.cz wrote:
> I may be wrong with my analysis, I am no expert on any of the things
> involved (bproc, autofs). Please correct me if I am wrong.

I'm not intimately familiar with autofs but your analysis sounds
dead-on to me.

> If I am right, there are several possible ways to avoid deadlock:
> 
> - Make modified autofs.o which is aware of bproc-related process group
>   tricks - autofs_oz_mode() should test for the same value which is
>   returned via getpgrp() (hope this can avoid node-head-node
>   communication). We should also verify whether setpgrp() used in
>   automount.c would work as expected.

This would work but it'd be somewhat unpleasant to actually do.  You'd
have suck part of bproc-x.x.x/kernel/bproc.h into the kernel source to
get the defintions for struct bproc_masq_proc_t.

> - Start automount outside the distributed PID space. I am not sure how
>   to do this, bproc is damn good in not letting you escape :-) - we
>   could modify /etc/inittab on node and signal init process and have our
>   automount process created this way?

This is the easiest way to get around the problem although there are
some drawbacks.  I've been pretty vehement about not providing hooks
for things like daemons to escape.  The rationale there is basically
that people would use those hooks if they were there. :)

> Any opinions and suggestions are more than welcome, especially
> comments on current handling of process groups in bproc (I know
> nothing about it).

The kernel lies to user process about process groups pretty much the
same way as with pids.

I don't have a nice solution handy for this one right now.

- Erik