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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7632C433FE for ; Mon, 27 Sep 2021 15:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A15F860F4A for ; Mon, 27 Sep 2021 15:00:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234986AbhI0PBf (ORCPT ); Mon, 27 Sep 2021 11:01:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234963AbhI0PBd (ORCPT ); Mon, 27 Sep 2021 11:01:33 -0400 Received: from mail-io1-xd30.google.com (mail-io1-xd30.google.com [IPv6:2607:f8b0:4864:20::d30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1E3DC061604 for ; Mon, 27 Sep 2021 07:59:55 -0700 (PDT) Received: by mail-io1-xd30.google.com with SMTP id b78so17844940iof.2 for ; Mon, 27 Sep 2021 07:59:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=uLXlWxVGEkoWhWtKQL0nyVslfQuFadAOO6/YckqDSmY=; b=zal/SEuPxMu7abv5ndknD9pJ0ARnlDA6g3ryVyTtf6NX3OB0gJIRG5BMYh9pl2XQYg SBElco7jAItOFK6H00ur5pNOlzc3luqe0kiqdg+yeSqs1R7vIN2x9OIByxjWa9PCNGZ0 ds5NomfpOQZjCJKT/npHgX2qDC+EBmd3N4rh8cgV0wxvwf0KlgRyPy8yt2LwnRaASAC+ idWHwOOOYtzpiAwXFrHyMInBbd2yFcZtKPXfRNRGvuPAslYuduCqzwUJ2KumpKqFjpkB CLCZaxgHKE4452c3fNhXDsK45q33skuRMxbFcwIo6PkoLY80IfQs0Zy6aEhrk1iIBsO8 Ne1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=uLXlWxVGEkoWhWtKQL0nyVslfQuFadAOO6/YckqDSmY=; b=mxdDz4+prgMQIlDVJBUoMsQktgD82HFM7wIxdNnDAWW82aTSeMnAi3hwgC/cw259IM NiSqX8uh+LbaWi2nMFGe25NKmEQVpZ5LRRWoLSZ6Khkx5rMIM/fdFCpSEz79187r+aT1 94bSxQl5L9rMNSHEOIWgkVGEB5531QhbG3D9H4fGG5WwyNyEBKGwQMBuqIwq4Ublz0Tm X5R+xue77WMtCXOV5bxUoFtG5e3bi19cT+vDqxV8uNrrbjwLSEU1bmRASwnCvaCTR5hO T1pZo946crqgwFn9zgSQvYdslnXxEAznKN4r5heDM6ERADjkj+qK74eigfa0Lg4CiaII CMOw== X-Gm-Message-State: AOAM531V6ZUT2Kb0RpN7EqLWuKo9WPWH8Cm13TK2uw6vwifbjncETTYO iDJpx9zjQkFn1RiLajAOcY3EEgIl88eySCWKZcA= X-Google-Smtp-Source: ABdhPJzonSZnI7uZROIUdxfxwL2NdQBUVpza4EcQdv+6Zxud55+HpFC2gT/RlzhvIRHbW7m+TAvoKg== X-Received: by 2002:a6b:5114:: with SMTP id f20mr106360iob.97.1632754794726; Mon, 27 Sep 2021 07:59:54 -0700 (PDT) Received: from [192.168.1.30] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id i8sm8971260ioi.29.2021.09.27.07.59.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Sep 2021 07:59:54 -0700 (PDT) Subject: Re: [GIT PULL] io_uring fixes for 5.15-rc3 From: Jens Axboe To: "Eric W. Biederman" Cc: Linus Torvalds , Oleg Nesterov , Al Viro , io-uring References: <0eeefd32-f322-1470-9bcf-0f415be517bd@kernel.dk> <87lf3iazyu.fsf@disp2133> Message-ID: <521162e9-c7e4-284e-e575-51c503c51793@kernel.dk> Date: Mon, 27 Sep 2021 08:59:53 -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: 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 9/27/21 8:29 AM, Jens Axboe wrote: > On 9/27/21 7:51 AM, Eric W. Biederman wrote: >> Jens Axboe writes: >> >>> On 9/25/21 5:05 PM, Linus Torvalds wrote: >>>> On Sat, Sep 25, 2021 at 1:32 PM Jens Axboe wrote: >>>>> >>>>> - io-wq core dump exit fix (me) >>>> >>>> Hmm. >>>> >>>> That one strikes me as odd. >>>> >>>> I get the feeling that if the io_uring thread needs to have that >>>> signal_group_exit() test, something is wrong in signal-land. >>>> >>>> It's basically a "fatal signal has been sent to another thread", and I >>>> really get the feeling that "fatal_signal_pending()" should just be >>>> modified to handle that case too. >>> >>> It did surprise me as well, which is why that previous change ended up >>> being broken for the coredump case... You could argue that the io-wq >>> thread should just exit on signal_pending(), which is what we did >>> before, but that really ends up sucking for workloads that do use >>> signals for communication purposes. postgres was the reporter here. >> >> The primary function get_signal is to make signals not pending. So I >> don't understand any use of testing signal_pending after a call to >> get_signal. >> >> My confusion doubles when I consider the fact io_uring threads should >> only be dequeuing SIGSTOP and SIGKILL. >> >> I am concerned that an io_uring thread that dequeues SIGKILL won't call >> signal_group_exit and thus kill the other threads in the thread group. >> >> What motivated removing the break and adding the fatal_signal_pending >> test? > > I played with this a bit this morning, and I agree it doesn't seem to be > needed at all. The original issue was with postgres, I'll give that a > whirl as well and see if we run into any unwarranted exits. My simpler > test case did not. Ran the postgres test, and we get tons of io-wq exiting on get_signal() returning true. Took a closer look, and it actually looks very much expected, as it's a SIGKILL to the original task. So it looks like I was indeed wrong, and this probably masked the original issue that was fixed in that series. I've been running with this: diff --git a/fs/io-wq.c b/fs/io-wq.c index c2360cdc403d..afd1db8e000d 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -584,10 +584,9 @@ static int io_wqe_worker(void *data) if (!get_signal(&ksig)) continue; - if (fatal_signal_pending(current) || - signal_group_exit(current->signal)) - break; - continue; + if (ksig.sig != SIGKILL) + printk("exit on sig! fatal? %d, sig=%d\n", fatal_signal_pending(current), ksig.sig); + break; } last_timeout = !ret; } and it's running fine and, as expected, we don't generate any printk activity as these are all fatal deliveries to the parent. -- Jens Axboe