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 A5FE2C43218 for ; Fri, 26 Apr 2019 17:40:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A42B206C1 for ; Fri, 26 Apr 2019 17:40:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726400AbfDZRkX (ORCPT ); Fri, 26 Apr 2019 13:40:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47990 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726315AbfDZRkW (ORCPT ); Fri, 26 Apr 2019 13:40:22 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 41B59CA1F5; Fri, 26 Apr 2019 17:40:22 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.159]) by smtp.corp.redhat.com (Postfix) with SMTP id EB69B60BF3; Fri, 26 Apr 2019 17:40:20 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 26 Apr 2019 19:40:21 +0200 (CEST) Date: Fri, 26 Apr 2019 19:40:19 +0200 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 v10 4/9] cgroup: cgroup v2 freezer Message-ID: <20190426174019.GB24755@redhat.com> References: <20190405174708.1010-1-guro@fb.com> <20190405174708.1010-5-guro@fb.com> <20190419151912.GA12152@redhat.com> <20190419161118.GA23357@tower.DHCP.thefacebook.com> <20190419162600.GC12228@redhat.com> <20190419165600.GC23357@tower.DHCP.thefacebook.com> <20190420105838.GA17468@redhat.com> <20190422221116.GA10341@tower.DHCP.thefacebook.com> <20190424154619.GG16167@redhat.com> <20190424220634.GA22896@tower.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190424220634.GA22896@tower.DHCP.thefacebook.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 26 Apr 2019 17:40:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/24, Roman Gushchin wrote: > > On Wed, Apr 24, 2019 at 05:46:19PM +0200, Oleg Nesterov wrote: > > > > OK, how about the ABSOLUTELY UNTESTED patch below? For the start. > > It looks good to me (and all freezer selftests pass). > > Just to be sure, is it a solution to avoid the busy loop in the signal handling > loop, right? Yes, > Because it doesn't allow to drop the ->frozen check from recalc(). Yes. Because we can race with unfreeze after leave_frozen(). > The JOBCTL_TRAP_FREEZE check without siglock initially looked dangerous to me, > but after some thoughts I didn't find any case when it's wrong. I think this is fine... Yes, JOBCTL_TRAP_FREEZE can be already set when we take siglock, but I don't think we need to recheck this flag. The only important thing (afaics) is that CGRP_FREEZE is stable under css_set_lock, so we can't wrongly set TRAP_FREEZE. > Do you prefer me to master a patch Yes please ;) Oleg.