kernel panic on HEAD from Oct. 4th sources

[Nicolas Thery]

2007/10/16, Peter Avalos <pavalos at theshell.com>:
> Just had this one last night:
>
> Fatal trap 12: page fault while in kernel mode
[...]
> #7  0xc018cb85 in fill_kinfo_proc (p=0xe8c21ba0, kp=0xec319628) at /usr/src/sys/kern/kern_kinfo.c:66

It looks like p->p_pgrp == NULL.

p_pgrp is checked against NULL in several other places in the kernel
(and in fbsd too), so a fix could be to do the same in
fill_kinfo_proc().

However, I don't understand how p_pgrp can be NULL.  AFAIU, it is
inherited from the parent process and set to NULL only when the
process is about to die (leaveprgp() called from kern_wait() just
before deleting the proc structure).  Could there be some race
condition?