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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47F2AC38142 for ; Mon, 23 Jan 2023 20:58:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232553AbjAWU6w (ORCPT ); Mon, 23 Jan 2023 15:58:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232690AbjAWU6n (ORCPT ); Mon, 23 Jan 2023 15:58:43 -0500 Received: from mail-wm1-x32b.google.com (mail-wm1-x32b.google.com [IPv6:2a00:1450:4864:20::32b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1523FDBEF for ; Mon, 23 Jan 2023 12:58:17 -0800 (PST) Received: by mail-wm1-x32b.google.com with SMTP id m15so10017620wms.4 for ; Mon, 23 Jan 2023 12:58:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:user-agent:mime-version:date:message-id:from :to:cc:subject:date:message-id:reply-to; bh=jP31T9len35tRIV6SSGMhQ3n8VcNE5DPSsO+Y5Dlli8=; b=Di8+yQeCLn3bmFLFg2gHqOmZSr+KeyZHhN94gE6YH0ZbI9AOg5LecrdYX5PbC+vLFn UZmcHVbcW0eMZx3zHMoH8az+yRiOS1EEjxAX0YadN6MtlkUacc2gKcBC6s3HF3MpR/Ko B+/hMs3LTMjuP/IjxVgdyZmM7L+jKHciti9XKBohrfrcfRfE9zH8dUiTLQlwJFCAV1XA 7RRQUNtUD0tjcR9drQJe9M9GHu2RxB2Ma28RL9w9GzeQdapW1sldQBzgdEv7JQ5mTo3B FHLw/h7+HUk9FI3/YBTPN3axwdiyz5uOlky3YiAOs7tXoRNPO1ODA1wlgoGW2t4hWRrA z7Qw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=jP31T9len35tRIV6SSGMhQ3n8VcNE5DPSsO+Y5Dlli8=; b=jEFWUaWAhHobkmwUYCYRLadxFSJy7I65971fusKO9A2gK406o6J3JqyM3vrdfd/8A5 hiUJCU3WMUp8o9XtesflTgKBns+g0LGDQwnW94t8sQN8S08QzJHg1wQ1zMKUNh/VoCM1 UIBXN5rsyHUipWIsV5dTXKA7yuW1gT8bq3u6hKtIdCMrvUY+7/hgYldRhPNia8eMFaoo lhyQKN8TsoFD3XUqxWR11ybyhsvUc7rY13iehsMFx/sIzvSne5VFnpEL8fC716h6pWCZ c9O8o/dCpqVaFQeFEn9xaKh+k8KidSfGXXR2MScpLYcJ8BXhRihnMKaP7U8YT3chmNnS U3bw== X-Gm-Message-State: AFqh2kpPVV3t4psQ9E5kj1XZBDVmy6qUUaPlWWo6trNwMb1S38ClX3LL NS/02LuLwrZMtQfrCY631KtrsYNAZ9w= X-Google-Smtp-Source: AMrXdXt1bkpvFleWR09z/Qu2mLcMj56ZUeIZape1qGZ8EGL16YrLypUgCYqM1mWrgmFFCZyOApCBtA== X-Received: by 2002:a05:600c:540c:b0:3cf:7704:50ce with SMTP id he12-20020a05600c540c00b003cf770450cemr24191972wmb.38.1674507495155; Mon, 23 Jan 2023 12:58:15 -0800 (PST) Received: from [192.168.8.100] (92.41.37.76.threembb.co.uk. [92.41.37.76]) by smtp.gmail.com with ESMTPSA id e18-20020a05600c449200b003da105437besm186220wmo.29.2023.01.23.12.58.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Jan 2023 12:58:14 -0800 (PST) Message-ID: <1575ad4b-d6c0-33e2-9dab-046094fd7b43@gmail.com> Date: Mon, 23 Jan 2023 20:56:54 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH for-next 1/7] io_uring: use user visible tail in io_uring_poll() To: Jens Axboe , io-uring@vger.kernel.org References: <228ffcbf30ba98856f66ffdb9a6a60ead1dd96c0.1674484266.git.asml.silence@gmail.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 1/23/23 18:25, Jens Axboe wrote: > On 1/23/23 7:37 AM, Pavel Begunkov wrote: >> We return POLLIN from io_uring_poll() depending on whether there are >> CQEs for the userspace, and so we should use the user visible tail >> pointer instead of a transient cached value. > > Should we mark this one for stable as well? Yeah, we can. It makes it to overestimate the number of ready CQEs and causes spurious POLLINs, but should be extremely rare and happen only on queue (but not wq wake up). -- Pavel Begunkov