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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 24677C04EB8 for ; Thu, 6 Dec 2018 13:18:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E780A20868 for ; Thu, 6 Dec 2018 13:18:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E780A20868 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bitron.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729636AbeLFNSy (ORCPT ); Thu, 6 Dec 2018 08:18:54 -0500 Received: from nov-007-i650.relay.mailchannels.net ([46.232.183.204]:16034 "EHLO nov-007-i650.relay.mailchannels.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728482AbeLFNSy (ORCPT ); Thu, 6 Dec 2018 08:18:54 -0500 X-Sender-Id: novatrend|x-authuser|juerg@bitron.ch Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 1957C2EC002B; Thu, 6 Dec 2018 13:18:48 +0000 (UTC) Received: from srv17.tophost.ch (swiss-ingress-3.mailchannels.ch [46.232.178.210]) by relay.mailchannels.net (Postfix) with ESMTPA id 158912EC0007; Thu, 6 Dec 2018 13:18:39 +0000 (UTC) X-Sender-Id: novatrend|x-authuser|juerg@bitron.ch Received: from srv17.tophost.ch (srv17.tophost.ch [193.33.128.141]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384) by 0.0.0.0:2500 (trex/5.15.2); Thu, 06 Dec 2018 13:18:48 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: novatrend|x-authuser|juerg@bitron.ch X-MailChannels-Auth-Id: novatrend X-Turn-Drop: 351b22812587cfd1_1544102327847_1743630459 X-MC-Loop-Signature: 1544102327847:3638496485 X-MC-Ingress-Time: 1544102327846 Received: from [80.219.231.201] (port=47716 helo=jzen.bitron.ch) by srv17.tophost.ch with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1gUtY5-00FJ5X-4q; Thu, 06 Dec 2018 14:18:37 +0100 Message-ID: <89a6b3a24412d385a816d7d981c60cb1e1bbc0ca.camel@bitron.ch> Subject: Re: [PATCH v4] signal: add taskfd_send_signal() syscall From: =?ISO-8859-1?Q?J=FCrg?= Billeter To: Florian Weimer Cc: Christian Brauner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, luto@kernel.org, arnd@arndb.de, ebiederm@xmission.com, serge@hallyn.com, jannh@google.com, akpm@linux-foundation.org, oleg@redhat.com, cyphar@cyphar.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, dancol@google.com, timmurray@google.com, linux-man@vger.kernel.org, keescook@chromium.org, tglx@linutronix.de, x86@kernel.org Date: Thu, 06 Dec 2018 14:18:36 +0100 In-Reply-To: <87pnue6bp2.fsf@oldenburg2.str.redhat.com> References: <20181206121858.12215-1-christian@brauner.io> <87h8fq7s84.fsf@oldenburg2.str.redhat.com> <87pnue6bp2.fsf@oldenburg2.str.redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-AuthUser: juerg@bitron.ch Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: On Thu, 2018-12-06 at 14:12 +0100, Florian Weimer wrote: > * Jürg Billeter: > > > On Thu, 2018-12-06 at 13:30 +0100, Florian Weimer wrote: > > > * Christian Brauner: > > > > > > > /* zombies */ > > > > Zombies can be signaled just as any other process. No special error will be > > > > reported since a zombie state is an unreliable state (cf. [3]). > > > > > > I still disagree with this analysis. If I know that the target process > > > is still alive, and it is not, this is a persistent error condition > > > which can be reliably reported. Given that someone might send SIGKILL > > > to the process behind my back, detecting this error condition could be > > > useful. > > > > As I understand it, kill() behaves the same way. I think it's good that > > this new syscall keeps the behavior as close as possible to kill(). > > No, kill does not behave in this way because the PID can be reused. > The error condition is not stable there. The PID can't be reused as long as it's a zombie. It can only be reused when it has been wait()ed for. Or am I misunderstanding something? Jürg