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=-6.6 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,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 9717AC433E1 for ; Fri, 21 Aug 2020 01:57:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F7B620748 for ; Fri, 21 Aug 2020 01:57:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="UuR52SF5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727104AbgHUB5n (ORCPT ); Thu, 20 Aug 2020 21:57:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40482 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726841AbgHUB5l (ORCPT ); Thu, 20 Aug 2020 21:57:41 -0400 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2184C061385 for ; Thu, 20 Aug 2020 18:57:41 -0700 (PDT) Received: by mail-pj1-x102e.google.com with SMTP id d4so136856pjx.5 for ; Thu, 20 Aug 2020 18:57:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=ZdHxIpFnJnE4SQXDnf56TBzsZjfHWRza2evXa2ElUWc=; b=UuR52SF5bQ7+X2utKQ10l44jrFcot/C66vLR3kDEQJLvhQvqGp9pGStvv8xahUxhrW REMGgh2um5Ke/Pn3ZAcKBc9RApqaHGo2bA9W/AeIRuDGu2QygFOnWgMC8LlxXWRWC4Lt eKRY1TY1BBKw1+hY+076J+WPvz0L5la5FbV+LMKypi8p/AnYJgyYPp5qS/SmuTgAKv2y PuBoWmXImjfxphr2dfQQIy++J0Vv5OUofep7Fqz7uB0j8L89PmFMxPzUnva2OawM235d oAqdN0MKVnPSxNcotAN7ZfVvju+afnr4Eo4ZMEze0XiixC6iaqlEVLZKZSrcBhM160n0 rtmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ZdHxIpFnJnE4SQXDnf56TBzsZjfHWRza2evXa2ElUWc=; b=AQPpbGBrafMBBJMI2Zy8XHUQtueSrnTv5F5TMvZjXGnyTwCmdDxBkfGWWoou9D/iza htLbBDxTWnOegvaCIaoTJbC+Og/67ddj3CBmkiR7wg4EYfpFgNPVLMnj8QxPvLAz22zD pF8z70wipykj37jsFTrdi6a+kitSTBQt5AYadrWMcLe+VawcFWmWug4odS08p/v6MYCA 0yKAh34svXGM3fFE23lU6IboenJ8a6VV9dPCgcHghSNhG3XiztzxhWezEZDbPC9HHueh sJYduNsXWyRSYQff1050jn76qVdalmPPVYPhPk3HLcKHwu8d4XiVYn4xsubJuGaOOnAY dUUA== X-Gm-Message-State: AOAM531bu/pExgu+oxCwINiIiVdKu9oHfXlyXhr+6rMNPaeEDFX1lc4s iNhescqYZUgxHP7PsoHxVSIknA== X-Google-Smtp-Source: ABdhPJw1QSgtMHrM3wE5R/Pib8lAjnHZpVhRQvhpmBZq9/husimrJh09By4MB0Y222kVJnz7sKDP0Q== X-Received: by 2002:a17:90b:509:: with SMTP id r9mr540171pjz.228.1597975059557; Thu, 20 Aug 2020 18:57:39 -0700 (PDT) Received: from [192.168.1.182] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id b6sm176642pjz.33.2020.08.20.18.57.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2020 18:57:38 -0700 (PDT) Subject: Re: Poll ring behavior broken by f0c5c54945ae92a00cdbb43bdf3abaeab6bd3a23 To: Glauber Costa , io-uring@vger.kernel.org, xiaoguang.wang@linux.alibaba.com References: From: Jens Axboe Message-ID: <8d8870de-909a-d05d-51a5-238f5c59764d@kernel.dk> Date: Thu, 20 Aug 2020 19:57:37 -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 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 8/20/20 6:46 PM, Glauber Costa wrote: > I have just noticed that the commit in $subject broke the behavior I > introduced in > bf3aeb3dbbd7f41369ebcceb887cc081ffff7b75 > > In this commit, I have explained why and when it does make sense to > enter the ring if there are no sqes to submit. > > I guess one could argue that in that case one could call the system > call directly, but it is nice that the application didn't have to > worry about that, had to take no conditionals, and could just rely on > io_uring_submit as an entry point. > > Since the author is the first to say in the patch that the patch may > not be needed, my opinion is that not only it is not needed but in > fact broke applications that relied on previous behavior on the poll > ring. > > Can we please revert? Yeah let's just revert it for now. Any chance you can turn this into a test case for liburing? Would help us not break this in the future. -- Jens Axboe