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 8C783C282DA for ; Wed, 17 Apr 2019 13:50:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 57B3320872 for ; Wed, 17 Apr 2019 13:50:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732303AbfDQNuH (ORCPT ); Wed, 17 Apr 2019 09:50:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39232 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729453AbfDQNuG (ORCPT ); Wed, 17 Apr 2019 09:50:06 -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 4178C3199386; Wed, 17 Apr 2019 13:50:06 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.38]) by smtp.corp.redhat.com (Postfix) with SMTP id DC5B160C64; Wed, 17 Apr 2019 13:50:03 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 17 Apr 2019 15:50:05 +0200 (CEST) Date: Wed, 17 Apr 2019 15:50:03 +0200 From: Oleg Nesterov To: Christian Brauner Cc: Jann Horn , "Eric W. Biederman" , Arnd Bergmann , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] signal: don't silently convert SI_USER signals to non-current pidfd Message-ID: <20190417135002.GF32622@redhat.com> References: <20190330021232.191205-1-jannh@google.com> <20190408131315.GA24111@redhat.com> <20190417130336.i55vmf3x6cby2mvi@brauner.io> <20190417131602.GE32622@redhat.com> <20190417131904.qjkv2xuenhcsz36l@brauner.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417131904.qjkv2xuenhcsz36l@brauner.io> 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 [10.5.110.41]); Wed, 17 Apr 2019 13:50:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/17, Christian Brauner wrote: > > On Wed, Apr 17, 2019 at 03:16:03PM +0200, Oleg Nesterov wrote: > > On 04/17, Christian Brauner wrote: > > > > > > On Mon, Apr 08, 2019 at 03:13:16PM +0200, Oleg Nesterov wrote: > > > > > > > > but perhaps it should always fail, even if task_pid(current) == pid. > > > > > > > > sys_rt_sigqueueinfo() allows to send any siginfo to yourself, but this is only needed > > > > for checkpoint/restart. > > > > > > Yes, that's why this was added. I would leave it in exactly because of > > > checkpoint/restart. > > > > I don't understand... > > > > c/r doesn't need this "feature" in pidfd_send_signal(), so it can be removed. > > But, > > Just out of curiosity: in what sense? They don't need it since they have > other ways of doing this Yes. The restarting process needs to "restore" the pending signals, including the signals with si_code >= 0. It does this using tgsigqueueinfo() and that is why we allow this if the signal sent to itself. So criu simply doesn't need pidfd_send_signal() to do this. And at the same time, > or they *can't* use it for some other reason Yes again. pidfd_send_signal() does kill_pid_info(), so it can't be used to restore the "per-thread" task->pending signals. Oleg.