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 2E466C433EF for ; Tue, 12 Apr 2022 03:20:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344196AbiDLDW7 (ORCPT ); Mon, 11 Apr 2022 23:22:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344515AbiDLDWv (ORCPT ); Mon, 11 Apr 2022 23:22:51 -0400 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E7531929C; Mon, 11 Apr 2022 20:20:35 -0700 (PDT) Received: by mail-pl1-f176.google.com with SMTP id c12so290709plr.6; Mon, 11 Apr 2022 20:20:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=7VT6OS2Zq3xIyfsj15Xb2jo5DCcrYgYdtW2QTDTUZ9g=; b=u8//jNtFowOhZUdEvLXp/EzMoDROrCLLgTc9P/uCD5/XajBtypiisidHZFaTWCyobb DDrDW8iymcRAiLEl6B74BUaQfdnFmKWejn7+syBvtHwpNW4JmL9gx68eWGGQ9uvwyIPk saHVko4KJ7zzZtfERVmLgWiMQsVWLrrJC6TCvvPjs1vVekZaHc0Fpp57/Dep4kU/97HF vV33yihku7kzpcW0XhziiHrEibAhrLfJc5wrPlM+pQlEEBFHmC/DaWlv9SLrOOVqy2uf 2ZdWpqymu06RpBlPNZjPzz1iErlw8j/O9Z9GeeLugccPz6NBjoGDAMXnV6Wl5CP35jMp Umsg== X-Gm-Message-State: AOAM531HHr+Khs4SKQGNWNyOp/TeQlYtrh4P6ULGeotOWTbRLUBvH9my IP0DmknsJjUoZScYQuWpJoM= X-Google-Smtp-Source: ABdhPJyX/yiluHvle7DFv3GYJFH8NJTwI9X6az29p1cn+XJQa4p+ob6jdQd4bAm14tyMXMOuWZQQwg== X-Received: by 2002:a17:903:110c:b0:14d:8859:5c8 with SMTP id n12-20020a170903110c00b0014d885905c8mr35109121plh.156.1649733634935; Mon, 11 Apr 2022 20:20:34 -0700 (PDT) Received: from ?IPV6:2601:647:4000:d7:feaa:14ff:fe9d:6dbd? ([2601:647:4000:d7:feaa:14ff:fe9d:6dbd]) by smtp.gmail.com with ESMTPSA id f20-20020a056a00229400b004fb16860af6sm37358440pfe.195.2022.04.11.20.20.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Apr 2022 20:20:34 -0700 (PDT) Message-ID: <7095eedb-91a7-e8d6-f30b-91aa65de3533@acm.org> Date: Mon, 11 Apr 2022 20:20:32 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH -next RFC v2 8/8] sbitmap: wake up the number of threads based on required tags Content-Language: en-US To: "yukuai (C)" , axboe@kernel.dk, andriy.shevchenko@linux.intel.com, john.garry@huawei.com, ming.lei@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com References: <20220408073916.1428590-1-yukuai3@huawei.com> <20220408073916.1428590-9-yukuai3@huawei.com> <6470d923-8fa5-cda1-e519-6f890cdcb00a@acm.org> <4c322eee-3ad9-812f-a341-aa5e91573912@huawei.com> <51aa71af-4c05-2991-5698-12014a4943d5@huawei.com> From: Bart Van Assche In-Reply-To: <51aa71af-4c05-2991-5698-12014a4943d5@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/9/22 00:01, yukuai (C) wrote: > For the race that new threads are waited after get_wake_nr() and before > wake_up_nr() in situation (b), I can't figure out how this can be > problematic [ ... ] If the atomic_dec_return() statement in __sbq_wake_up() returns a value that is less than or equal to zero, wake_batch waiters should be woken up or I/O will hang until sbitmap_queue_wake_all() is called. That last function should not be called unless there is no alternative. Thanks, Bart.