Oh, duh.  The race is obvious.  Sorry for the confusion there.

The BUG_ON's were useful for debugging, since they trigger on a lot of
errors, but they _also_ trigger on some unlikely (but valid) races.

So just remove them - just fall through to the regular exit code after
core-dumping (which does everything right).
Signed-off-by: Linus Torvalds <torvalds@osdl.org>