Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754376Ab0K2Q6u (ORCPT ); Mon, 29 Nov 2010 11:58:50 -0500 Received: from mtagate5.uk.ibm.com ([194.196.100.165]:38835 "EHLO mtagate5.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751069Ab0K2Q6t (ORCPT ); Mon, 29 Nov 2010 11:58:49 -0500 Subject: Re: [patch 4/4] taskstats: Export "cdata_acct" with taskstats From: Michael Holzheu Reply-To: holzheu@linux.vnet.ibm.com To: Oleg Nesterov Cc: Shailabh Nagar , Andrew Morton , Peter Zijlstra , John stultz , Thomas Gleixner , Balbir Singh , Martin Schwidefsky , Heiko Carstens , Roland McGrath , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org In-Reply-To: <20101129164329.GA16648@redhat.com> References: <20101119201108.269346583@linux.vnet.ibm.com> <20101119201144.871656307@linux.vnet.ibm.com> <20101125132639.GB25836@redhat.com> <1290705675.1941.73.camel@holzheu-laptop> <20101129164329.GA16648@redhat.com> Content-Type: text/plain; charset="us-ascii" Organization: IBM Date: Mon, 29 Nov 2010 17:58:37 +0100 Message-ID: <1291049917.1935.14.camel@holzheu-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 982 Lines: 26 Hello Oleg, On Mon, 2010-11-29 at 17:43 +0100, Oleg Nesterov wrote: > > I just did it like it is done in e.g. fs/proc/base.c (proc_pid_limits). > > Can we remove the locking there, too? > > We can certainly remove more siglock's which were previously > needed to access ->signal. > > This particular one is just wrong. We need task_lock(group_leader) > to read signal->rlim atomically. However, it is not trivial to do > this correctly. Probably we should ignore this minor problem. > > In any case, this ->siglock buys nothing today. But at least to get the two values cutime and cstime consistent we need the siglock? There could be a parallel update for tsk->signal->cutime/cstime, while the taskstats are created, no? Michael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/