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 6AA80C433C1 for ; Fri, 26 Mar 2021 15:09:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41EA561A24 for ; Fri, 26 Mar 2021 15:09:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230098AbhCZPJU (ORCPT ); Fri, 26 Mar 2021 11:09:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230006AbhCZPIu (ORCPT ); Fri, 26 Mar 2021 11:08:50 -0400 Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::2:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 040FAC0613AA; Fri, 26 Mar 2021 08:08:49 -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=4yDQYIgruStTTwVNerqYw9NDLnJwOdualiGA88b99fo=; b=vYSEUsHaGPvLvTeeYmRjnxnALV uHYGOwdeJ/ZN9wvp1NkTR30qSqELpmst23bvGpi1xObbSEsYi1j3VlavoEyJS9yjLkEcgPh0rlvl0 AOCY3ozRvq7F9tEUpbcoPbGnBnY4W8cxoZGnz47rvkNHcQQWMoTuTUNK8/cv4vCoD8pyZECTBL+Fb c9iBZOjc5Uh7nCMmOJVtT+SAA1exh5A6+UWN8NXDFVjcGh2hcAxnCMVANbAOFZWxZURznCOKX0wvn CU0EDk6xQPF1k8DsOCzmW8RzfjsGRZTEB7NwvGvw64BAJT6cx0WGBs0QTYr44rdyTjqSfCyYHQJNT ihNjU5WdDm+5UGpCPrf88E1zzMlU8dudeu7SKILYh6WNfQDieWxnMn3N5Uu0jcxQfz3q+cSv/nfju DUItD8f9TpBDMm41xKLM+atBrOxLyd9rA9Egym6gvwr1nWZrKxAsqidgnqNj636EqdWG1HjMHdpfO S5CW1dC3Rc0FtkC7ya4R9MLY; 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 1lPo4t-0003Kd-Rg; Fri, 26 Mar 2021 15:08:47 +0000 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> From: Stefan Metzmacher Subject: Re: [PATCH 0/6] Allow signals for IO threads Message-ID: <6a171373-e901-ae97-41fd-29445c3fe89e@samba.org> Date: Fri, 26 Mar 2021 16:08:44 +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: <1304f480-a8db-44cf-5d89-aa9b99efdcd7@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 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. metze