From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756517AbcEaWxI (ORCPT ); Tue, 31 May 2016 18:53:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750750AbcEaWxH (ORCPT ); Tue, 31 May 2016 18:53:07 -0400 Date: Wed, 1 Jun 2016 00:53:03 +0200 From: Oleg Nesterov To: Michal Hocko Cc: linux-mm@kvack.org, Tetsuo Handa , David Rientjes , Vladimir Davydov , Andrew Morton , LKML Subject: Re: [PATCH 1/6] proc, oom: drop bogus task_lock and mm check Message-ID: <20160531225303.GE26582@redhat.com> References: <1464613556-16708-1-git-send-email-mhocko@kernel.org> <1464613556-16708-2-git-send-email-mhocko@kernel.org> <20160530174324.GA25382@redhat.com> <20160531073227.GA26128@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160531073227.GA26128@dhcp22.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 31 May 2016 22:53:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/31, Michal Hocko wrote: > > Oleg has pointed out that can simplify both oom_adj_write and > oom_score_adj_write even further and drop the sighand lock. The only > purpose of the lock was to protect p->signal from going away but this > will not happen since ea6d290ca34c ("signals: make task_struct->signal > immutable/refcountable"). Sorry for confusion, I meant oom_adj_read() and oom_score_adj_read(). As for oom_adj_write/oom_score_adj_write we can remove it too, but then we need to ensure (say, using cmpxchg) that unpriviliged user can not not decrease signal->oom_score_adj_min if its oom_score_adj_write() races with someone else (say, admin) which tries to increase the same oom_score_adj_min. If you think this is not a problem - I am fine with this change. But please also update oom_adj_read/oom_score_adj_read ;) Oleg.