linux-kernel - Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all threads in process group

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Message-Id: <1181337147.21409.42.camel@farscape.rchland.ibm.com>
Date:	Fri, 08 Jun 2007 16:12:26 -0500
From:	Will Schmidt <will_schmidt@...t.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linuxppc-dev@...abs.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Oleg Nesterov <oleg@...sign.ru>,
	Anton Blanchard <anton@...ba.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all
	threads in process group

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@...t.ibm.com> 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. 

Thanks,

-Will

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