Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all threads in process group
From: Oleg Nesterov
Date: Wed Jun 13 2007 - 11:51:33 EST
On 06/08, Eric W. Biederman wrote:
> Will Schmidt <will_schmidt@xxxxxxxxxxxx> writes:
> > On Fri, 2007-06-08 at 12:32 -0700, Andrew Morton wrote:
> >> On Fri, 08 Jun 2007 14:19:18 -0500
> >> Will Schmidt <will_schmidt@xxxxxxxxxxxx> wrote:
> >> > > > > zap_other_threads() requires tasklist_lock.
> >> >
> >> In fact, it's probably the case that rcu_read_lock() is now sufficient
> >> locking coverage for zap_other_threads() (cc's people).
> >> It had better be, because do_group_exit() forgot to take tasklist_lock. It
> >> is perhaps relying upon spin_lock()'s hidden rcu_read_lock() properties
> >> without so much as a code comment, which would be somewhat nasty of it.
> >> You could perhaps just call do_group_exit() from within the fault
> >> handler,
> >> btw.
> > Yup, so looks like I can actually replace the existing do_exit() call
> > with do_group_exit(). I'll sit on this for a bit to give other folks a
> > chance to comment on which lock call is sufficient, read_lock() or
> > rcu_read_lock(), etc; and do_group_exit()'s issue with taking
> > tasklist_lock.
> No. The rcu_read_lock is not sufficient.
> Yes. sighand->siglock is enough, and we explicitly take it in
> do_group_exit before calling zap_other_threads.
Yes, we don't need tasklist_lock (or rcu_read_lock).
de_thread() calls zap_other_threads() under tasklist_lock, but this
is because we can change child_reaper.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/