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=-10.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 261EEC433DB for ; Fri, 26 Mar 2021 15:10:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEADF61A18 for ; Fri, 26 Mar 2021 15:10:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230083AbhCZPKX (ORCPT ); Fri, 26 Mar 2021 11:10:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230297AbhCZPKG (ORCPT ); Fri, 26 Mar 2021 11:10:06 -0400 Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 718B9C0613AA for ; Fri, 26 Mar 2021 08:10:06 -0700 (PDT) Received: by mail-io1-xd31.google.com with SMTP id n21so5716622ioa.7 for ; Fri, 26 Mar 2021 08:10:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=utfxfNwabcfbVuwRPgcfwhwS17kOd25iCl9MxY83iVE=; b=dMq5Lpev1I4olY/DhGk/CchPEmq+vul7WGppqcV63oKm07OlwWX/iltIar3WXuem8D b5d3lH5OB3kl3r6+3QjE5rLkThFpdis9+16KUhZJZtKNxiPV0SpIWCCgbtBoPiFWyUnk ekZWioz+48lrFIArkFd9I7R5ICbZQ9l6691Q0WIp2A5c227EdzW7pbbXnSZHlFdDROqG ZaOKN3QbT05Q1gtlRnDFit/hVUXoWRvy1SMe/1SJNBq4++NiQXeFA3XXhXbBUTuqdolo 7nMZ3ytzrG3xr4wjhTZq4pOzbXBDvZSHamJ0+rFnWc+R/s25tzGsE97fPEx/9Rr6GWQr cG4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=utfxfNwabcfbVuwRPgcfwhwS17kOd25iCl9MxY83iVE=; b=aD7c2V1uSdM0c3uidKabASAp+ANLpC0nSsHfSExJhBzcxZkndconB3GT3pOmDI7AFk GqjmpcLQGakDi5HvS8rmczGV9ddqyaHJmFivxGb7CfWtqyh6Ym16fazMkbftD0V5lXRc tNjBXT5Vr9LMzoJmR9kgTHKK6vDTZ840BZVLd+kfQ9e58r5/sQR3YfdfJn25gDoKwpE7 R9Kn2v0pWGBIDz5+Va+2NRhEqbBkT8D/lpsG9o3ZAKqotGGjB7GRz7fbGPJoGW0dwwoC k4H/kQHyPNSm5VWR/cda1WbJ2o9Sv4ygVsFwGZJaMEm3tv4R7qWi2ZqdfIKVBEj9pDYE uHQA== X-Gm-Message-State: AOAM533u2NgQFdLAcw0T6knLPF3hAu91oxtkPLvD54oekAKQ+/iiSUpG dR9qoAzPUu14op47Nl0XBV8D9w== X-Google-Smtp-Source: ABdhPJxKNEhuBgzkLLp9/Bj9ZO9o7cOlxWsoSKMrhuTImZ7Tcdk4OGSZBz2EIlfybr6jDxJmSImp6A== X-Received: by 2002:a02:cb4b:: with SMTP id k11mr12410255jap.144.1616771405872; Fri, 26 Mar 2021 08:10:05 -0700 (PDT) Received: from [192.168.1.30] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id 14sm4623798ilt.54.2021.03.26.08.10.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Mar 2021 08:10:05 -0700 (PDT) Subject: Re: [PATCH 0/6] Allow signals for IO threads To: Stefan Metzmacher , 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: Jens Axboe Message-ID: Date: Fri, 26 Mar 2021 09:10:05 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <6a171373-e901-ae97-41fd-29445c3fe89e@samba.org> 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 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. -- Jens Axboe