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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 7BE06C433DB for ; Fri, 12 Mar 2021 21:32:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F01564F8D for ; Fri, 12 Mar 2021 21:32:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235164AbhCLVbs (ORCPT ); Fri, 12 Mar 2021 16:31:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235227AbhCLVbY (ORCPT ); Fri, 12 Mar 2021 16:31:24 -0500 Received: from mail-pg1-x534.google.com (mail-pg1-x534.google.com [IPv6:2607:f8b0:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BB32C061574 for ; Fri, 12 Mar 2021 13:31:23 -0800 (PST) Received: by mail-pg1-x534.google.com with SMTP id t37so5893241pga.11 for ; Fri, 12 Mar 2021 13:31:23 -0800 (PST) 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=O28SrWxFoKuT+W8E0Bqi2pxmRgQgeT6wV86Murma5d8=; b=XLWHVYdgsxc8SX+b7SVgTuijmRFGe387AAc68g28G60jTR2WMSCHlAATbKxn5RI1FY Zq35BW1/j/QEeLrPK1sGs/f9V9Rj7avlJj8VRXkkU/J0PHl+Fdciv+gJIxXOG396OUE9 szU7lEkVEg1MPjnmHdGQ/ymx4nF7fE1+oywY5x22fa4CibcLyGcBt/RGKeIGcMFd7sEe ekvDjSZcSIY/bsZ6eyadmsc8uU4Ofh0n2PcfEPtv7VrTVo6uZWOhhcbsIUhISuc2IIVn 4ucM276FQsdcsUAIb0UO+73YuZxfgJWPegc3vx2J5Nj41NvNq2IjGhAn+k1T9nHW1bJT Bcag== 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=O28SrWxFoKuT+W8E0Bqi2pxmRgQgeT6wV86Murma5d8=; b=oFmc3PFmDCwFmmGvomYDq6fKM+oKc4B3hWoYudK8fVNjwJkfXJQlKHn8VnGyl/xsLi gey8PC5oB2Vso5CfmYZzhFnYo4YIsxoK4p9w+CQHkQC/ZtolQoNzRDS1hV8RffimA2KL rhn5kpV143TAq9IjnG08//rxNUZCJXS3elv4zR56XgZc9koy04kW30NgU0Om9NpszmXD 8P+/21immdbgLVpJn8VoXB/mTW4Ke+vQuG0tuRRi6O/0TocUm8/XQ89m/Enp3O4wQP+U QR6LvRlMm+E6VtXoY6TJeGK4Pk1KDfE3/s3FmHlAa86A2n25JL/oDeSoLeyIW5ZTNYL0 oDHA== X-Gm-Message-State: AOAM533at8x7K4bByQYw1lof26+mbjlxvTgRUYMsrFq0kmr60ARAtrx0 64zeI9hD2u4eRIFbJHg/7JNV9hdUPAZDmw== X-Google-Smtp-Source: ABdhPJzT+iBMcPshD3FbOHrhFBAI5OPCckt/kOx9Yz6R42v6hHs2EQgiKS1IG9mALnlt9emr3VKpng== X-Received: by 2002:a63:6642:: with SMTP id a63mr13285896pgc.333.1615584682514; Fri, 12 Mar 2021 13:31:22 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id 9sm6157075pgy.79.2021.03.12.13.31.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Mar 2021 13:31:22 -0800 (PST) Subject: Re: [GIT PULL] io_uring fixes for 5.12-rc3 To: Linus Torvalds Cc: io-uring References: From: Jens Axboe Message-ID: <647a0f56-3dd5-2eeb-8d57-2180f2ab1bca@kernel.dk> Date: Fri, 12 Mar 2021 14:31:21 -0700 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 3/12/21 2:17 PM, Linus Torvalds wrote: > On Fri, Mar 12, 2021 at 11:48 AM Jens Axboe wrote: >> >> - Make IO threads unfreezable by default, on account of a bug report >> that had them spinning on resume. Honestly not quite sure why thawing >> leaves us with a perpetual signal pending (causing the spin), but for >> now make them unfreezable like there were in 5.11 and prior. > > That "not quite sure" doesn't exactly give my the warm and fuzzies, > but not being new is ok, I guess. But I'd really like you to try to > figure out what is actually going on. Oh I agree, which is why I wanted to bring it up as I do feel like we're just working around this issue. > I'm _guessing_ it's just that now those threads are user threads, and > then the freezing logic expects them to freeze/thaw using a signal > machinery or something like that. And that doesn't work when there is > no signal handling for those threads. > > But it would be good to _know_. That's very much my guess too, since the symptom is that we loop all the time because we think there's a signal pending. I am investigating it and reached out to Rafael to try and figure this out, but at the same time I did not want to have an -rc3 that caused resume issues for users. Hence the "let's just disable freezing for now so that things work, get it fixed for real when we can" kind of solution. -- Jens Axboe