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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 380FCC433DB for ; Thu, 25 Mar 2021 19:35:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF09861A32 for ; Thu, 25 Mar 2021 19:35:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229581AbhCYTeu (ORCPT ); Thu, 25 Mar 2021 15:34:50 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:52784 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229616AbhCYTep (ORCPT ); Thu, 25 Mar 2021 15:34:45 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out01.mta.xmission.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1lPVki-008Fxh-5l; Thu, 25 Mar 2021 13:34:44 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=fess.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1lPVkh-0000za-GY; Thu, 25 Mar 2021 13:34:43 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Jens Axboe Cc: io-uring@vger.kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, oleg@redhat.com, metze@samba.org References: <20210325164343.807498-1-axboe@kernel.dk> Date: Thu, 25 Mar 2021 14:33:43 -0500 In-Reply-To: <20210325164343.807498-1-axboe@kernel.dk> (Jens Axboe's message of "Thu, 25 Mar 2021 10:43:41 -0600") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lPVkh-0000za-GY;;;mid=;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18mfvkY8hIovTxtqn4/JaJ6qC3aJXoeS3A= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 0/2] Don't show PF_IO_WORKER in /proc//task/ 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) Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Jens Axboe writes: > Hi, > > Stefan reports that attaching to a task with io_uring will leave gdb > very confused and just repeatedly attempting to attach to the IO threads, > even though it receives an -EPERM every time. This patchset proposes to > skip PF_IO_WORKER threads as same_thread_group(), except for accounting > purposes which we still desire. > > We also skip listing the IO threads in /proc//task/ so that gdb > doesn't think it should stop and attach to them. This makes us consistent > with earlier kernels, where these async threads were not related to the > ring owning task, and hence gdb (and others) ignored them anyway. > > Seems to me that this is the right approach, but open to comments on if > others agree with this. Oleg, I did see your messages as well on SIGSTOP, > and as was discussed with Eric as well, this is something we most > certainly can revisit. I do think that the visibility of these threads > is a separate issue. Even with SIGSTOP implemented (which I did try as > well), we're never going to allow ptrace attach and hence gdb would still > be broken. Hence I'd rather treat them as separate issues to attack. A quick skim shows that these threads are not showing up anywhere in proc which appears to be a problem, as it hides them from top. Sysadmins need the ability to dig into a system and find out where all their cpu usage or io's have gone when there is a problem. I general I think this argues that these threads should show up as threads of the process so I am not even certain this is the right fix to deal with gdb. Eric