BUG_ONs in signal.c?

[Jesse Barnes <jbarnes@engr.sgi.com>]

I recently saw a bug where someone hit the BUG_ON in signal.c after the 
do_coredump code (in my kernel "kernel BUG at signal.c:1614").  After looking 
at it a bit, it seems that we drop the sighand lock prior to calling into the 
core dump routine, which leaves the task vulnerable to having it's group_exit 
or group_exit_code changed either during the coredump or shortly after, 
causing one of the BUG_ONs to trip (in this particular case it was the 
group_exit_code != code check).  Are these BUG_ON checks necessary anymore?  
Or should we be holding the sighand lock all the way until we call do_exit or 
do_group_exit?  Or something else?

Thanks,
Jesse