From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD391C433DF for ; Thu, 20 Aug 2020 14:37:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6D2F207DE for ; Thu, 20 Aug 2020 14:37:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gS+H1fyq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728284AbgHTOhD (ORCPT ); Thu, 20 Aug 2020 10:37:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28129 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727794AbgHTOgs (ORCPT ); Thu, 20 Aug 2020 10:36:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597934205; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ifENA3PpreyA2aD6j5lQuTCVzurPXcU/o20ccZ4XeWM=; b=gS+H1fyq/Tmd7Y6eyO6af9InvVhQM8TdxbnmGoBqmi296J7VtKUK0mwLC89f8Fsli2EnMf 5nM6fSze0demD5cva0MrQzdGhfJG0aMvDRhRpxY70aG7DWO8yoqTGrItHlgmLmvlXGwus1 dP/lgHE3H8pSRxv0AS94MTp0Jk8KFEw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-379-pPnBEFoCPHGUzDPKC_ycdA-1; Thu, 20 Aug 2020 10:36:41 -0400 X-MC-Unique: pPnBEFoCPHGUzDPKC_ycdA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C974B1084C97; Thu, 20 Aug 2020 14:36:37 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.73]) by smtp.corp.redhat.com (Postfix) with SMTP id 821D916E2A; Thu, 20 Aug 2020 14:36:28 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 20 Aug 2020 16:36:37 +0200 (CEST) Date: Thu, 20 Aug 2020 16:36:27 +0200 From: Oleg Nesterov To: "Eric W. Biederman" Cc: Michal Hocko , Suren Baghdasaryan , christian.brauner@ubuntu.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, esyr@redhat.com, christian@kellner.me, areber@redhat.com, shakeelb@google.com, cyphar@cyphar.com, adobriyan@gmail.com, akpm@linux-foundation.org, gladkov.alexey@gmail.com, walken@google.com, daniel.m.jordan@oracle.com, avagin@gmail.com, bernd.edlinger@hotmail.de, john.johansen@canonical.com, laoar.shao@gmail.com, timmurray@google.com, minchan@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary Message-ID: <20200820143626.GD4546@redhat.com> References: <20200820002053.1424000-1-surenb@google.com> <87zh6pxzq6.fsf@x220.int.ebiederm.org> <20200820124241.GJ5033@dhcp22.suse.cz> <87lfi9xz7y.fsf@x220.int.ebiederm.org> <87d03lxysr.fsf@x220.int.ebiederm.org> <20200820132631.GK5033@dhcp22.suse.cz> <874koxxwn5.fsf@x220.int.ebiederm.org> <20200820140451.GC4546@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200820140451.GC4546@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 08/20, Oleg Nesterov wrote: > > On 08/20, Eric W. Biederman wrote: > > > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1139,6 +1139,10 @@ static int exec_mmap(struct mm_struct *mm) > > vmacache_flush(tsk); > > task_unlock(tsk); > > if (old_mm) { > > + mm->oom_score_adj = old_mm->oom_score_adj; > > + mm->oom_score_adj_min = old_mm->oom_score_adj_min; > > + if (tsk->vfork_done) > > + mm->oom_score_adj = tsk->vfork_oom_score_adj; > > too late, ->vfork_done is NULL after mm_release(). > > And this can race with __set_oom_adj(). Yes, the current code is racy too, > but this change adds another race, __set_oom_adj() could already observe > ->mm != NULL and update mm->oom_score_adj. ^^^^^^^^^^^^ I meant ->mm == new_mm. And another problem. Suppose we have if (!vfork()) { change_oom_score(); exec(); } the parent can be killed before the child execs, in this case vfork_oom_score_adj will be lost. Oleg.