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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 45323C433FF for ; Fri, 2 Aug 2019 13:30:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1617E217D4 for ; Fri, 2 Aug 2019 13:30:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404221AbfHBNak (ORCPT ); Fri, 2 Aug 2019 09:30:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50806 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729469AbfHBNYX (ORCPT ); Fri, 2 Aug 2019 09:24:23 -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 DDD0E307D90E; Fri, 2 Aug 2019 13:24:22 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id E9F0560BF4; Fri, 2 Aug 2019 13:24:20 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 2 Aug 2019 15:24:22 +0200 (CEST) Date: Fri, 2 Aug 2019 15:24:20 +0200 From: Oleg Nesterov To: Adrian Reber Cc: Christian Brauner , Eric Biederman , Pavel Emelianov , Jann Horn , Dmitry Safonov <0x7f454c46@gmail.com>, linux-kernel@vger.kernel.org, Andrei Vagin , Mike Rapoport , Radostin Stoyanov Subject: Re: [PATCH v2 1/2] fork: extend clone3() to support CLONE_SET_TID Message-ID: <20190802132419.GD20111@redhat.com> References: <20190731161223.2928-1-areber@redhat.com> <20190731174135.GA30225@redhat.com> <20190802072511.GD18263@dcbz.redhat.com> <20190802124738.GC20111@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190802124738.GC20111@redhat.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 [10.5.110.48]); Fri, 02 Aug 2019 13:24:23 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/02, Oleg Nesterov wrote: > > On 08/02, Adrian Reber wrote: > > > > On Wed, Jul 31, 2019 at 07:41:36PM +0200, Oleg Nesterov wrote: > > > But the main question is how it can really help if ns->level > 0, unlikely > > > CRIU will ever need to clone the process with the same pid_nr == set_tid > > > in the ns->parent chain. > > > > Not sure I understand what you mean. For CRIU only the PID in the PID > > namespace is relevant. > > If it runs "inside" this namespace. But in this case alloc_pid() should > use nr == set_tid only once in the main loop, when i == ns->level. and I just noticed that your patch does exactly this, it clears set_tid after the 1st usage when i == ns->level. > > > So may be kernel_clone_args->set_tid should be pid_t __user *set_tid_array? > > > Or I missed something ? > > > > Not sure why and how an array would be needed. Could you give me some > > more details why you think this is needed. > > IIURC, criu can restore the process tree along with nested pid namespaces. > > how can this patch help in this case? > > But again, perhaps I missed something. I forgot everything about criu. Yes... I guess in this case it can "safely" modify ns_last_pid in the child namespaces it needs to create. So Adrian, sorry for confusion, I think your patch is fine. Oleg.