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 C503FC43381 for ; Thu, 21 Feb 2019 16:44:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BBC72084D for ; Thu, 21 Feb 2019 16:44:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727481AbfBUQoG (ORCPT ); Thu, 21 Feb 2019 11:44:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725767AbfBUQoG (ORCPT ); Thu, 21 Feb 2019 11:44:06 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 50F793082E91; Thu, 21 Feb 2019 16:44:06 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.152]) by smtp.corp.redhat.com (Postfix) with SMTP id F10B56090C; Thu, 21 Feb 2019 16:44:04 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 21 Feb 2019 17:44:06 +0100 (CET) Date: Thu, 21 Feb 2019 17:44:04 +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 v8 4/7] cgroup: cgroup v2 freezer Message-ID: <20190221164403.GB26064@redhat.com> References: <20190219220252.4906-1-guro@fb.com> <20190219220252.4906-5-guro@fb.com> <20190220144202.GB9477@redhat.com> <20190220221423.GA17163@castle.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190220221423.GA17163@castle.DHCP.thefacebook.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Thu, 21 Feb 2019 16:44:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20, Roman Gushchin wrote: > > On Wed, Feb 20, 2019 at 03:42:02PM +0100, Oleg Nesterov wrote: > > On 02/19, Roman Gushchin wrote: > > > > > > @@ -2363,7 +2419,8 @@ bool get_signal(struct ksignal *ksig) > > > * we should notify the parent, prepare_signal(SIGCONT) encodes > > > * the CLD_ si_code into SIGNAL_CLD_MASK bits. > > > */ > > > - if (unlikely(signal->flags & SIGNAL_CLD_MASK)) { > > > + if (unlikely(signal->flags & SIGNAL_CLD_MASK) & > > > + !(current->jobctl & JOBCTL_TRAP_FREEZE)) { > > > > Hmm, why? > > If a process is going from the stopped to the frozen state, it looks like > it's better to delay parent's notification up to the moment when it will > actually run. Perhaps I missed something but I do not understand why it is really better, at least why it deserves this (small but still) complication... OK, if nothing else, suppose that SIGCONT races with cgroup_do_freeze(true). With or without this change CLD_CONTINUED can be reported or not depending on /dev/random, do we really care? Oleg.