Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752336Ab0KYN2z (ORCPT ); Thu, 25 Nov 2010 08:28:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51616 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751834Ab0KYN2y (ORCPT ); Thu, 25 Nov 2010 08:28:54 -0500 Date: Thu, 25 Nov 2010 14:21:55 +0100 From: Oleg Nesterov To: Michael Holzheu 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 Subject: Re: [patch 3/4] taskstats: Introduce cdata_acct for complete cumulative accounting Message-ID: <20101125132155.GA25836@redhat.com> References: <20101119201108.269346583@linux.vnet.ibm.com> <20101119201144.542948128@linux.vnet.ibm.com> <20101123165951.GA5938@redhat.com> <1290678022.1941.29.camel@holzheu-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1290678022.1941.29.camel@holzheu-laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1800 Lines: 54 On 11/25, Michael Holzheu wrote: > > Hello Oleg, > > On Tue, 2010-11-23 at 17:59 +0100, Oleg Nesterov wrote: > > On 11/19, Michael Holzheu wrote: > > > TODO: > > > ----- > > > With this patch we take the siglock twice. First for the dead task > > > and second for the parent of the dead task. This give the following > > > lockdep warning (probably a lockdep annotation is needed here): > > > > And we already discussed this ;) We do not need 2 siglock's, only > > parent's. Just move the callsite in __exit_signal() down, under > > another (lockless) group_dead check. > > > > Or I missed something? > > The problem with moving this down to the second group_dead check is that > after __unhash_process() is called, pid_alive(tsk) which is checked in > thread_group_cputime() returns false. Therefore we always get zero CPU > times. I see, thanks. > So I probably have to introduce a second group_dead check at the > beginning of __exit_signal(): Probably... But in fact this reminds we should cleanup this code somehow. By the time we call thread_group_times() there are no other threads. > My personal feeling is that probably the only acceptable thing would be > to make the new behavior configurable with a sysctl and define the > default as it currently is (POSIX compliant). > > This would only introduce two additional checks in __exit_signal() and > wait_task_zombie() and would not add any new fields to the > signal_struct. Yeah, it would be nice to avoid new fields. Hmm. Somehow I forgot about 4/4, please see another email... Oleg. -- 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/