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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A65B1C433DB for ; Fri, 26 Mar 2021 15:12:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82FFD61937 for ; Fri, 26 Mar 2021 15:12:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230051AbhCZPL7 (ORCPT ); Fri, 26 Mar 2021 11:11:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230070AbhCZPL3 (ORCPT ); Fri, 26 Mar 2021 11:11:29 -0400 Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::2:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB40BC0613B2; Fri, 26 Mar 2021 08:11:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=samba.org; s=42; h=Date:Message-ID:From:Cc:To; bh=X6+Ia+AcMqWgp5WM6pGVUxgYvK/J+DRXTGwO3A7jLr4=; b=vVdTk3Jp09NhTqG45pZr2o9fuw YdqG1WuyZ8By4vBvqh8n7AwuCVHTx0sGhmdQ+fabsZ1nR03YxXvRHnXpHcpycJ+z87UbnjYbLs0dh jFFpSvkZEgZket0uHlDc7C+1fHzQ17q0tGV5BvwcSGIwxKDe9Iuni97Ak7QnCrCdTWSjhHG7ciyKn DAeA7QQQjSeZ0Flqp1XwOPVe/T/OmYOZD4I6MUXGHIFaRb39ElSQaGKnh3Zq2p8MmM9kjh9hH07M3 7/UAkgIaD1Bd1hrcr14SVpAruE972kwnGyPF8+fn8O+Q3aU/AGHiP37f9m9eZADKfQ1A4z3ywk34N Ip6JYh9fdmkUKH21t/OaFtixDzMNYVMSxsrQ8KMtGnTNej011hUIxTlGS607qw4Xa6XuACWpQvx7p wx/std7cVg0MBS/y62RLVs7KBcve0Bwkrb51wm3uw+tFgjusT320G4BaWxtddw4xfKzwzgDvWtjXp zv6xQoPg7QtL3V1OWYg7yjna; Received: from [127.0.0.2] (localhost [127.0.0.1]) by hr2.samba.org with esmtpsa (TLS1.3:ECDHE_RSA_CHACHA20_POLY1305:256) (Exim) id 1lPo7S-0003Le-Gb; Fri, 26 Mar 2021 15:11:27 +0000 Subject: Re: [PATCH 0/6] Allow signals for IO threads To: Jens Axboe , io-uring@vger.kernel.org Cc: torvalds@linux-foundation.org, ebiederm@xmission.com, oleg@redhat.com, linux-kernel@vger.kernel.org References: <20210326003928.978750-1-axboe@kernel.dk> <8efd9977-003b-be65-8ae2-4b04d8dd1224@samba.org> <0c91d9e7-82cd-bec2-19ae-cc592ec757c6@kernel.dk> <66fa3cfc-4161-76fe-272e-160097f32a53@kernel.dk> <67a83ad5-1a94-39e5-34c7-6b2192eb7edb@samba.org> <0396df33-7f91-90c8-6c0d-8a3afd3fff3c@kernel.dk> <1304f480-a8db-44cf-5d89-aa9b99efdcd7@kernel.dk> <6a171373-e901-ae97-41fd-29445c3fe89e@samba.org> From: Stefan Metzmacher Message-ID: <018c3185-bd13-1085-e738-9b5010252215@samba.org> Date: Fri, 26 Mar 2021 16:11:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Am 26.03.21 um 16:10 schrieb Jens Axboe: > On 3/26/21 9:08 AM, Stefan Metzmacher wrote: >> Am 26.03.21 um 15:55 schrieb Jens Axboe: >>> On 3/26/21 8:53 AM, Jens Axboe wrote: >>>> On 3/26/21 8:45 AM, Stefan Metzmacher wrote: >>>>> Am 26.03.21 um 15:43 schrieb Stefan Metzmacher: >>>>>> Am 26.03.21 um 15:38 schrieb Jens Axboe: >>>>>>> On 3/26/21 7:59 AM, Jens Axboe wrote: >>>>>>>> On 3/26/21 7:54 AM, Jens Axboe wrote: >>>>>>>>>> The KILL after STOP deadlock still exists. >>>>>>>>> >>>>>>>>> In which tree? Sounds like you're still on the old one with that >>>>>>>>> incremental you sent, which wasn't complete. >>>>>>>>> >>>>>>>>>> Does io_wq_manager() exits without cleaning up on SIGKILL? >>>>>>>>> >>>>>>>>> No, it should kill up in all cases. I'll try your stop + kill, I just >>>>>>>>> tested both of them separately and didn't observe anything. I also ran >>>>>>>>> your io_uring-cp example (and found a bug in the example, fixed and >>>>>>>>> pushed), fwiw. >>>>>>>> >>>>>>>> I can reproduce this one! I'll take a closer look. >>>>>>> >>>>>>> OK, that one is actually pretty straight forward - we rely on cleaning >>>>>>> up on exit, but for fatal cases, get_signal() will call do_exit() for us >>>>>>> and never return. So we might need a special case in there to deal with >>>>>>> that, or some other way of ensuring that fatal signal gets processed >>>>>>> correctly for IO threads. >>>>>> >>>>>> And if (fatal_signal_pending(current)) doesn't prevent get_signal() from being called? >>>>> >>>>> Ah, we're still in the first get_signal() from SIGSTOP, correct? >>>> >>>> Yes exactly, we're waiting in there being stopped. So we either need to >>>> check to something ala: >>>> >>>> relock: >>>> + if (current->flags & PF_IO_WORKER && fatal_signal_pending(current)) >>>> + return false; >>>> >>>> to catch it upfront and from the relock case, or add: >>>> >>>> fatal: >>>> + if (current->flags & PF_IO_WORKER) >>>> + return false; >>>> >>>> to catch it in the fatal section. >>> >>> Can you try this? Not crazy about adding a special case, but I don't >>> think there's any way around this one. And should be pretty cheap, as >>> we're already pulling in ->flags right above anyway. >>> >>> diff --git a/kernel/signal.c b/kernel/signal.c >>> index 5ad8566534e7..5b75fbe3d2d6 100644 >>> --- a/kernel/signal.c >>> +++ b/kernel/signal.c >>> @@ -2752,6 +2752,15 @@ bool get_signal(struct ksignal *ksig) >>> */ >>> current->flags |= PF_SIGNALED; >>> >>> + /* >>> + * PF_IO_WORKER threads will catch and exit on fatal signals >>> + * themselves. They have cleanup that must be performed, so >>> + * we cannot call do_exit() on their behalf. coredumps also >>> + * do not apply to them. >>> + */ >>> + if (current->flags & PF_IO_WORKER) >>> + return false; >>> + >>> if (sig_kernel_coredump(signr)) { >>> if (print_fatal_signals) >>> print_fatal_signal(ksig->info.si_signo); >>> >> >> I guess not before next week, but if it resolves the problem for you, >> I guess it would be good to get this into rc5. > > It does, I pushed out a new branch. I'll send out a v2 series in a bit. Great, thanks! Any chance to get the "cmdline" hiding included? metze