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=-11.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,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 8DF15C43457 for ; Mon, 19 Oct 2020 16:50:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29CA7222EC for ; Mon, 19 Oct 2020 16:50:37 +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="Cj5PKu+w" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730638AbgJSQug (ORCPT ); Mon, 19 Oct 2020 12:50:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730632AbgJSQug (ORCPT ); Mon, 19 Oct 2020 12:50:36 -0400 Received: from mail-il1-x142.google.com (mail-il1-x142.google.com [IPv6:2607:f8b0:4864:20::142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4624C0613CE for ; Mon, 19 Oct 2020 09:50:34 -0700 (PDT) Received: by mail-il1-x142.google.com with SMTP id j13so873311ilc.4 for ; Mon, 19 Oct 2020 09:50:34 -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=CZGaBpF+XG3vwH05pw71qWVZZZgkknNclI0WAqZQgSY=; b=Cj5PKu+w0E1ji2GDGbABo9oM6ap9FJejYSREnFl6+ofXwjpvE9kCJnPziy+E874NK/ szGIej57JZ2r/5FjwTBHGITuDJX2stUxMPJU/jNvsGlpnexnBQLkQc/nQYOQnIWgjj8h VjRwo0HQJ6mzT0EG7UEBPWuqJLBltMHx3zpNhUckZMNqejeUYoAkfSgdKDiJWWsEjxvx oUiwGGaJSSw51hLsWIgVFsTOD0k/+bKavrp3vQqq8+nHyQ5GoyBIKdHZ+XyokBWdp9Kx rPhfMb7//pnZHlZAqmnSn8XCJ9fcU5Tvt/TSeXgqZUN9J+DTtx3QdN6OFkr6t+jO5IBu r8OA== 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=CZGaBpF+XG3vwH05pw71qWVZZZgkknNclI0WAqZQgSY=; b=THhE4ZMZImahV0SdIngCF6YIhQ0u8xmgivmuw24KSHxIaVsy/TT5upPRPmpWt3mUf5 bHT6pw5pKZuGzGi/FAOsD7Q0ocyF/54b6EiUGda2lmDH4BC8rzggD9RVR7d61A62eLIr YCXJ/gJk7pF94umKNUoorwSpbgWVQS5S7SofAXES6c6pukfCMqCR8/DqTERICwW7uO2X afnu/qIDuAHZTdL14QCi/dhE9vkX2gMsd3FKXMWnBgMkoJZKNhh5qf7lhYh5rdUGKiK1 B21RiQfCFXYeY7t8NguGkKroUmIan/EoolBN+/+XIG2uQsrKKRD4ks4VQG6P3BP9/WfE NHfw== X-Gm-Message-State: AOAM532Y4q/zj9SrfVMPp++aM3oouVWTjJvuqpGqykxsCK6fecOCaH3X ZaiMeXMEwfIMJMUAr7TlLMFgKg== X-Google-Smtp-Source: ABdhPJyfh3SKt/Cs5dzhr5eRA3fFFyIBq9MlPQ3JP992LoEki9nwODqJhoNorbsGwiT26Ui9pkjp1Q== X-Received: by 2002:a92:bb9c:: with SMTP id x28mr766407ilk.77.1603126233747; Mon, 19 Oct 2020 09:50:33 -0700 (PDT) Received: from [192.168.1.30] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id c2sm275921iot.52.2020.10.19.09.50.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Oct 2020 09:50:33 -0700 (PDT) Subject: Re: [PATCH] block/elevator: reduce the critical section To: Hui Su , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20201019164246.GA79115@rlk> From: Jens Axboe Message-ID: Date: Mon, 19 Oct 2020 10:50:32 -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: <20201019164246.GA79115@rlk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 10/19/20 10:42 AM, Hui Su wrote: > 1.reduce the critical section in elevator_get(). > 2.reduce the critical section in elevator_get_by_features(). > 3.remove the found variable. > > the elv_list_lock is used to protect the elv_list, > and the operations of elevator_type does not need > to be protected. > > Signed-off-by: Hui Su > --- > block/elevator.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) > > diff --git a/block/elevator.c b/block/elevator.c > index 293c5c81397a..727902b31954 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -151,11 +151,11 @@ static struct elevator_type *elevator_get(struct request_queue *q, > spin_lock(&elv_list_lock); > e = elevator_find(name, q->required_elevator_features); > } > + spin_unlock(&elv_list_lock); > > if (e && !try_module_get(e->elevator_owner)) > e = NULL; > > - spin_unlock(&elv_list_lock); > return e; > } What happens for: A B spin_unlock(&elv_list_lock); rmmod -> elv_unregister(); try_module_get(); -- Jens Axboe