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 5F889C04EB8 for ; Thu, 6 Dec 2018 14:50:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C13D20850 for ; Thu, 6 Dec 2018 14:50:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C13D20850 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com 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 S1730938AbeLFOuk (ORCPT ); Thu, 6 Dec 2018 09:50:40 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:44743 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731382AbeLFOrM (ORCPT ); Thu, 6 Dec 2018 09:47:12 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gUuvl-0006KF-SQ; Thu, 06 Dec 2018 07:47:09 -0700 Received: from ip68-227-174-240.om.om.cox.net ([68.227.174.240] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gUuvk-0007EM-V4; Thu, 06 Dec 2018 07:47:09 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Florian Weimer Cc: =?utf-8?Q?J=C3=BCrg?= Billeter , Christian Brauner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, luto@kernel.org, arnd@arndb.de, 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 References: <20181206121858.12215-1-christian@brauner.io> <87h8fq7s84.fsf@oldenburg2.str.redhat.com> <87pnue6bp2.fsf@oldenburg2.str.redhat.com> <87efaun587.fsf@xmission.com> <877egm6a7v.fsf@oldenburg2.str.redhat.com> Date: Thu, 06 Dec 2018 08:46:57 -0600 In-Reply-To: <877egm6a7v.fsf@oldenburg2.str.redhat.com> (Florian Weimer's message of "Thu, 06 Dec 2018 14:44:36 +0100") Message-ID: <87bm5yiufy.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1gUuvk-0007EM-V4;;;mid=<87bm5yiufy.fsf@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.240;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19jtjKamkrEUK9Q6nfr2VyLBcCUuaxvkmM= X-SA-Exim-Connect-IP: 68.227.174.240 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v4] signal: add taskfd_send_signal() syscall X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Florian Weimer writes: > * Eric W. Biederman: > >> Floriam are you seeing a problem with this behavior or the way Christian >> was describing it? > > My hope is that you could use taskfd_send_signal one day to send a > signal to a process which you *known* (based on how you've written your > application) should be running and not in a zombie state, and get back > an error if it has exited. > > If you get this error, only then you wait on the process, using the file > descriptor you have, and run some recovery code. > > Wouldn't that be a reasonable approach once we've got task descriptors? Getting an error back if the target was a zombie does seem reasonable, as in principle it is an easy thing to notice, and post zombie once the process has been reaped we definitely get an error back. I also agree that it sounds like an extension, as changing the default would violate the princile of least surprise. Eric