ptcwrite panic (with dump)

[Doug White]

On Sun, 8 May 2005, Kris Kennaway wrote:

> $2 = (struct pgrp *) 0x0

Looks like t_pgrp became NULL between us checking it and us inspecting the
list attached to it. Nice.

Try moving the sx_slock(&proctree_lock); grab above the tp->t_pgrp NULL
check and add a sx_sunlock(&proctree_lock); inside that if() block.

I don't know if proctree_lock or the per-tty mutex protects the t_pgrp
item in struct tty.  In any case we need to pick up some lock to keep it
from going away :-)

I'll bash up a draft patch for discussion.

-- 
Doug White                    |  FreeBSD: The Power to Serve
dwhite at gumbysoft.com          |  www.FreeBSD.org