Date: Mon, 20 Feb 2006 09:49:11 -0800
From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Roland McGrath <roland@redhat.com>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 2/2] fix kill_proc_info() vs fork() theoretical race
Message-ID: <20060220174911.GE1480@us.ibm.com>
Reply-To: paulmck@us.ibm.com
References: <43E77D3C.C967A275@tv-sign.ru> <20060214223214.GG1400@us.ibm.com> <43F3352C.E2D8F998@tv-sign.ru> <43F37D56.2D7AB32F@tv-sign.ru> <20060216192617.GF1296@us.ibm.com> <43F4E6EC.3B9F91C4@tv-sign.ru> <20060216195341.GG1296@us.ibm.com> <43F4EC88.D8B2DEE5@tv-sign.ru> <20060218020659.GH1291@us.ibm.com> <43F76538.16BBA317@tv-sign.ru>
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On Sat, Feb 18, 2006 at 09:19:36PM +0300, Oleg Nesterov wrote:
> "Paul E. McKenney" wrote:
> > 
> > On Fri, Feb 17, 2006 at 12:20:08AM +0300, Oleg Nesterov wrote:
> > > "Paul E. McKenney" wrote:
> > > >
> > > > The other thing to think through is tkill on a thread/process while it
> > > > is being created.  I believe that this is OK, since thread-specific
> > > > kill must target a specific thread, so does not do the traversal.
> > >
> > > Also, tkill was not converted to use rcu_read_lock yet, it still
> > > takes tasklist_lock, so I think it is safe.
> > 
> > I suspect that tkill will eventually need to avoid tasklist_lock...  ;-)
> 
> Ok, I am sending a couple of preparation patches for this.
> 
> Paul, I didn't beleive you when you started this work. Now I think
> we can avoid tasklist AND cleanup the code in many places. I am glad
> I was wrong.

And I am very glad that you are working this -- you have found some
approaches that are much better than those I would have come up with!

> Btw,
> >
> > firing off some steamroller tests on it.
> 
> Could you point me to these tests?

http://www.rdrop.com/users/paulmck/projects/steamroller/

Contributions of additional tests very welcome!

							Thanx, Paul
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