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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 719E7C433DF for ; Fri, 21 Aug 2020 00:46:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42B1620702 for ; Fri, 21 Aug 2020 00:46:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=datadoghq.com header.i=@datadoghq.com header.b="AQfdq51K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726347AbgHUAqf (ORCPT ); Thu, 20 Aug 2020 20:46:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725859AbgHUAqe (ORCPT ); Thu, 20 Aug 2020 20:46:34 -0400 Received: from mail-yb1-xb30.google.com (mail-yb1-xb30.google.com [IPv6:2607:f8b0:4864:20::b30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF31DC061385 for ; Thu, 20 Aug 2020 17:46:32 -0700 (PDT) Received: by mail-yb1-xb30.google.com with SMTP id q16so152974ybk.6 for ; Thu, 20 Aug 2020 17:46:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=datadoghq.com; s=google; h=mime-version:from:date:message-id:subject:to; bh=YpwVRjYKfQSKC+37NS+1EsbQDFqOk82fhgEI7gmadM0=; b=AQfdq51KTNUhV6pH8Kmo715x+zLvnEyP2b8AIy64dNGDgAl14RSmV53v8b/wB/J6SL QVS0de8//QAHRikDUHNyfmRH6JL15QB2S8jLSEAIAS4TeUyHwJIWCXjVwErtvMFb6gng LppvCyPq7oaJWwO4q8Pw6bMSTizpZmv/gyFOs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=YpwVRjYKfQSKC+37NS+1EsbQDFqOk82fhgEI7gmadM0=; b=Ri2+1YWho6FRC8nb7DbJi/+QUptcRH/0LAyyHZwGNsGXZT7cCtNOVN4gpbdPG33KOw lx2eRzyZrEO7jhp3euXrbKzX1kGLTbGqD1SZ8+UOV9qDTpxcmlBfW2eA6d0nw+9ra08U YzJdcQc1i7xvBn7YF6/yYkePSNTNHFnb2mDM+5UJvM7vp6CEZSVVULfQBRxtzf8MaeLr ak4n0ZxHbkeMAhx41wTt61tFF/yCGxgvIwZ0bRr3MH0XF24MUcXtSnfp4bGJBnJVicyj LMugIkzTj6F1n0jT3AWcoxEKzEkfJxE/KEB6WkZGMyizi4R7FSI7aJiWY/RZRSMw4sqn fqHw== X-Gm-Message-State: AOAM532IfoQy4XvXtZC3pPCM4ZKXfisNkizIXdvhgoaRpwFOtzJtnx5U 5Kk67RtfceQkK/7A1Kln9TEUrKWb4KHECqK4DjzSZXHMQzIc92k7 X-Google-Smtp-Source: ABdhPJwOwggducIhSqYj6HAwcBw8U4MOBSV/Tn9rl+sWAptIxjlyPEd1RikNUrFKU3evQR5yj1OK4viXcMzu3eqmAQ0= X-Received: by 2002:a25:ce07:: with SMTP id x7mr607030ybe.18.1597970789097; Thu, 20 Aug 2020 17:46:29 -0700 (PDT) MIME-Version: 1.0 From: Glauber Costa Date: Thu, 20 Aug 2020 20:46:18 -0400 Message-ID: Subject: Poll ring behavior broken by f0c5c54945ae92a00cdbb43bdf3abaeab6bd3a23 To: io-uring@vger.kernel.org, axboe@kernel.dk, xiaoguang.wang@linux.alibaba.com Content-Type: text/plain; charset="UTF-8" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 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?