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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 7B47BC3A59C for ; Fri, 16 Aug 2019 15:31:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A0C5206C1 for ; Fri, 16 Aug 2019 15:31:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727345AbfHPPbJ (ORCPT ); Fri, 16 Aug 2019 11:31:09 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:42668 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727311AbfHPPbJ (ORCPT ); Fri, 16 Aug 2019 11:31:09 -0400 Received: by mail-pg1-f195.google.com with SMTP id p3so3108121pgb.9 for ; Fri, 16 Aug 2019 08:31:09 -0700 (PDT) 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=xOQ4k2CvMo9pbAvK8uHRZ8OYCQz54RC9e1oMPDiG7jY=; b=BL5+/x9zE+W9grgJxjvtl8dAJkpBy1lnTOFTqjxwtgXrxlgi2HsqQ6B6Pm7ngNfGQE Nmlgj/0rnyKw3Aedl64XzOW1MVVaYyXwjr5Fg8Iy6IZpUV2nQ8qoRDxdKTTgDDavZC9L pZA2almds9NwxtpVPEOrXp42ma3kZBXZiJfW/51UMKfxoeRU4pUBViwrG/LRMgnSbBR2 thf7nYwKLVxAhUuB6PKv2ezyqXvQ2yTkrsdp5qz6sq5HUe1SllaKNlSay12u9eQK8gQS kVza+Z2hKPQ9cTc36jXTmo3a1DDaXXCKlL/hfz7SRI0bbd5LiFiIKbS7ZCv8hGKo71iR IuBA== X-Gm-Message-State: APjAAAWrleAvTL8p9U1E04ILs+qXTih+qPWGnRC31jqqqPKFQT0z1oXA eG4acZvQ+EqGB7O+ZLLdjMo= X-Google-Smtp-Source: APXvYqyKQK6fzSUVq+Fgge51661p8+1YAiW2J4vS/qYX67oGWI6ebhKqR6mezJkVJG3wpVbObBJMAw== X-Received: by 2002:a63:29c4:: with SMTP id p187mr8465112pgp.330.1565969468675; Fri, 16 Aug 2019 08:31:08 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id 65sm5363254pgf.30.2019.08.16.08.31.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Aug 2019 08:31:07 -0700 (PDT) Subject: Re: [PATCH] block: don't acquire .sysfs_lock before removing mq & iosched kobjects To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org, Greg KH , Mike Snitzer References: <20190816135506.29253-1-ming.lei@redhat.com> From: Bart Van Assche Message-ID: <14a9ae85-0d65-483d-30f7-d692c4058e46@acm.org> Date: Fri, 16 Aug 2019 08:31:06 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190816135506.29253-1-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 8/16/19 6:55 AM, Ming Lei wrote: > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 977c659dcd18..46f033b48917 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -1021,6 +1021,7 @@ EXPORT_SYMBOL_GPL(blk_register_queue); > void blk_unregister_queue(struct gendisk *disk) > { > struct request_queue *q = disk->queue; > + bool has_elevator; > > if (WARN_ON(!q)) > return; > @@ -1035,8 +1036,9 @@ void blk_unregister_queue(struct gendisk *disk) > * concurrent elv_iosched_store() calls. > */ > mutex_lock(&q->sysfs_lock); > - > blk_queue_flag_clear(QUEUE_FLAG_REGISTERED, q); > + has_elevator = q->elevator; > + mutex_unlock(&q->sysfs_lock); blk_queue_flag_clear() modifies queue flags atomically so no need to hold sysfs_lock around calls of that function. > @@ -1044,16 +1046,13 @@ void blk_unregister_queue(struct gendisk *disk) > */ > if (queue_is_mq(q)) > blk_mq_unregister_dev(disk_to_dev(disk), q); > - mutex_unlock(&q->sysfs_lock); > > kobject_uevent(&q->kobj, KOBJ_REMOVE); > kobject_del(&q->kobj); > blk_trace_remove_sysfs(disk_to_dev(disk)); > > - mutex_lock(&q->sysfs_lock); > - if (q->elevator) > + if (has_elevator) > elv_unregister_queue(q); > - mutex_unlock(&q->sysfs_lock); Have you considered to move the q->elevator check into elv_unregister_queue() such that no new 'has_elevator' variable has to be introduced in this function? Thanks, Bart.