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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 5FBBFC433DF for ; Thu, 20 Aug 2020 12:41:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 443F6207DA for ; Thu, 20 Aug 2020 12:41:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729559AbgHTMlc (ORCPT ); Thu, 20 Aug 2020 08:41:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:37594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729346AbgHTMlM (ORCPT ); Thu, 20 Aug 2020 08:41:12 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5D0EAAF0F; Thu, 20 Aug 2020 12:41:37 +0000 (UTC) Date: Thu, 20 Aug 2020 14:41:09 +0200 From: Michal Hocko To: Christian Brauner Cc: Oleg Nesterov , Suren Baghdasaryan , 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, ebiederm@xmission.com, 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: <20200820124109.GI5033@dhcp22.suse.cz> References: <20200820002053.1424000-1-surenb@google.com> <20200820105555.GA4546@redhat.com> <20200820111349.GE5033@dhcp22.suse.cz> <20200820113023.rjxque4jveo4nj5o@wittgenstein> <20200820114245.GH5033@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200820114245.GH5033@dhcp22.suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 20-08-20 13:42:56, Michal Hocko wrote: > On Thu 20-08-20 13:30:23, Christian Brauner wrote: [...] > > trying to rely on set_bit() and test_bit() in copy_mm() being atomic and > > then calling it where Oleg said after the point of no return. > > No objections. Would something like the following work for you? diff --git a/kernel/fork.c b/kernel/fork.c index 9177a76bf840..25b83f0912a6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1403,15 +1403,6 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) if (clone_flags & CLONE_VM) { mmget(oldmm); mm = oldmm; - if (!(clone_flags & CLONE_SIGHAND)) { - /* We need to synchronize with __set_oom_adj */ - mutex_lock(&oom_adj_lock); - set_bit(MMF_PROC_SHARED, &mm->flags); - /* Update the values in case they were changed after copy_signal */ - tsk->signal->oom_score_adj = current->signal->oom_score_adj; - tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min; - mutex_unlock(&oom_adj_lock); - } goto good_mm; } @@ -1818,6 +1809,19 @@ static __always_inline void delayed_free_task(struct task_struct *tsk) free_task(tsk); } +static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk) +{ + if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) == CLONE_VM) { + /* We need to synchronize with __set_oom_adj */ + mutex_lock(&oom_adj_lock); + set_bit(MMF_PROC_SHARED, &mm->flags); + /* Update the values in case they were changed after copy_signal */ + tsk->signal->oom_score_adj = current->signal->oom_score_adj; + tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min; + mutex_unlock(&oom_adj_lock); + } +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2290,6 +2294,8 @@ static __latent_entropy struct task_struct *copy_process( trace_task_newtask(p, clone_flags); uprobe_copy_process(p, clone_flags); + copy_oom_score_adj(clone_flags, p); + return p; bad_fork_cancel_cgroup: -- Michal Hocko SUSE Labs