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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 D7F09C43381 for ; Thu, 14 Feb 2019 16:26:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADE64222DE for ; Thu, 14 Feb 2019 16:26:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2502736AbfBNQ0T (ORCPT ); Thu, 14 Feb 2019 11:26:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388556AbfBNQ0R (ORCPT ); Thu, 14 Feb 2019 11:26:17 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B2B5A10F86; Thu, 14 Feb 2019 16:26:16 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.152]) by smtp.corp.redhat.com (Postfix) with SMTP id 49B4A600C1; Thu, 14 Feb 2019 16:26:15 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 14 Feb 2019 17:26:15 +0100 (CET) Date: Thu, 14 Feb 2019 17:26:13 +0100 From: Oleg Nesterov To: Roman Gushchin Cc: Roman Gushchin , Tejun Heo , Kernel Team , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v6 4/7] cgroup: cgroup v2 freezer Message-ID: <20190214162612.GC19102@redhat.com> References: <20181222000307.28231-1-guro@fb.com> <20181222000307.28231-5-guro@fb.com> <20190125122713.GA18218@redhat.com> <20190130165200.GA4131@redhat.com> <20190211213036.GA26063@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211213036.GA26063@tower.DHCP.thefacebook.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 14 Feb 2019 16:26:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/11, Roman Gushchin wrote: > > On Wed, Jan 30, 2019 at 05:52:01PM +0100, Oleg Nesterov wrote: > > > > Worse, this looks just wrong. In the latter case, cgroup becomes CGRP_FROZEN > > right after a 2nd task migrates to this cgroup, before this new task calls > > do_freezer_trap() or cgroup_enter_stopped(). > > You're right. So, it looks like the problem is in the equation > nr_tasks_frozen + nr_tasks_stopped == nr_tasks_to_freeze , > because a task can be frozen and stopped simultaneously. > > So, basically it has to be > nr_tasks_frozen + nr_tasks_stopped >= nr_tasks_to_freeze instead. It seems you didn't read the paragraph above, or I missed something... How can "frozen + stopped >= to_freeze" fix the problem with the falsely true CGRP_FROZEN ? Oleg.