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 B9FF2C43381 for ; Fri, 22 Feb 2019 16:34:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 86F1F20700 for ; Fri, 22 Feb 2019 16:34:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726991AbfBVQep (ORCPT ); Fri, 22 Feb 2019 11:34:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47420 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726019AbfBVQeo (ORCPT ); Fri, 22 Feb 2019 11:34:44 -0500 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 7FEED58586; Fri, 22 Feb 2019 16:34:44 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.152]) by smtp.corp.redhat.com (Postfix) with SMTP id 1F41E60BE6; Fri, 22 Feb 2019 16:34:42 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 22 Feb 2019 17:34:44 +0100 (CET) Date: Fri, 22 Feb 2019 17:34:42 +0100 From: Oleg Nesterov To: Tejun Heo Cc: Roman Gushchin , Roman Gushchin , Kernel Team , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v8 0/7] freezer for cgroup v2 Message-ID: <20190222163441.GA5596@redhat.com> References: <20190219220252.4906-1-guro@fb.com> <20190220143748.GA9477@redhat.com> <20190220220020.GA16335@castle.DHCP.thefacebook.com> <20190221162923.GA26064@redhat.com> <20190221173422.GY50184@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190221173422.GY50184@devbig004.ftw2.facebook.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 [10.5.110.39]); Fri, 22 Feb 2019 16:34:44 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 02/21, Tejun Heo wrote: > > So, I really wanna avoid allowing userspace to cause D state sleeps. ... > ptrace support is a lot less important than kill for sure but if at > all possible I think it'd be better to have it Tejun, I agree it would be better. I did not argue with that. The question is how this can be implemented. And how much uglifications^W complications in the core kernel code this needs. > To summarize, the ideal result is the frozen state to be "stuck in > jobctl stop loop" Not sure I understand, but I don't think this can work... Let me repeat, imo the freezer should be "reliable", it shouldn't stuck in CGRP_FREEZE state forever if, say, it races with vfork(). And personally I think this is more important than (very limited) ptrace support. So I think it too should somehow interact with freezable_schedule/etc. Oleg.