I just did a quick audit of the use of exit_state and the EXIT_* bit
macros.  I guess I didn't really review these changes very closely when you
did them originally.  :-(

I found several places that seem like lossy cases of query-replace without
enough thought about the code.  Linus has previously said the >= tests
ought to be & tests instead.  But for exit_state, it can only ever be 0,
EXIT_DEAD, or EXIT_ZOMBIE--so a nonzero test is actually the same as
testing & (EXIT_DEAD|EXIT_ZOMBIE), and maybe its code is a tiny bit better.
 The case like in choose_new_parent is just confusing, to have the
always-false test for EXIT_* bits in ->state there too.

The two cases in wants_signal and do_process_times are actual regressions
that will give us back old bugs in race conditions.  These places had
s/TASK/EXIT/ but not s/state/exit_state/, and now there tests for exiting
tasks are now wrong and never catching them.  I take it back: there is no
regression in wants_signal in practice I think, because of the PF_EXITING
test that makes the EXIT_* state checks superfluous anyway.  So that is
just another cosmetic case of confusing code.  But in do_process_times,
there is that SIGXCPU-while-exiting race condition back again.
Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>