mm: oom: do not reap task if there are live threads in threadgroup

If the current process is exiting, we don't invoke oom killer, instead
we give it access to memory reserves and try to reap its mm in case
nobody is going to use it.  There's a mistake in the code performing
this check - we just ignore any process of the same thread group no
matter if it is exiting or not - see try_oom_reaper.  Fix it.

Link: http://lkml.kernel.org/r/1464087628-7318-1-git-send-email-vdavydov@virtuozzo.com


Fixes: 3ef22dff ("oom, oom_reaper: try to reap tasks which skip regular OOM killer path")Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>