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Date: Wed, 28 Dec 2005 10:33:45 -0800
From: Ravikiran G Thirumalai <kiran@scalex86.org>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Christoph Lameter <clameter@engr.sgi.com>,
       Shai Fultheim <shai@scalex86.org>, Nippun Goel <nippung@calsoftinc.com>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>
Subject: Re: [rfc][patch] Avoid taking global tasklist_lock for single threadedprocess at getrusage()
Message-ID: <20051228183345.GA3755@localhost.localdomain>
References: <43AD8AF6.387B357A@tv-sign.ru> <Pine.LNX.4.62.0512271220380.27174@schroedinger.engr.sgi.com> <43B2874F.F41A9299@tv-sign.ru>
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On Wed, Dec 28, 2005 at 03:38:39PM +0300, Oleg Nesterov wrote:
> Christoph Lameter wrote:
> > 
> > On Sat, 24 Dec 2005, Oleg Nesterov wrote:
> > 
> > > I can't understand this. 'p' can do clone(CLONE_THREAD) immediately
> > > after 'if (!thread_group_empty(p))' check.
> > 
> > Only if p != current. As discussed later the lockless approach is
> > intened to only be used if p == current.
> 
> Unless I missed something this function (getrusage_both) is called
> from wait_noreap_copyout,

Hi Oleg,
Yes, this patch needs to be reworked.  I am on it.  I'd also missed that
p->signal was protected by the tasklist_lock.  Thanks for pointing it out.
I will put out the modified version soon.

Thanks,
Kiran