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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS 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 275F4C6778D for ; Tue, 11 Sep 2018 14:13:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF14C20880 for ; Tue, 11 Sep 2018 14:13:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Q3gDY39m" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF14C20880 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727997AbeIKTNG (ORCPT ); Tue, 11 Sep 2018 15:13:06 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:60404 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727010AbeIKTNG (ORCPT ); Tue, 11 Sep 2018 15:13:06 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w8BE4Ssr143720; Tue, 11 Sep 2018 14:13:31 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=lmGimO6mmUFDrITB/4MbPtLU/wF3eZKfQkeqvIlBCoQ=; b=Q3gDY39mrqC1zNf9Y9QMzXpJo3wGLT+n2qYXS2oELf4WPYZXpb08EsYySKYZlfB6tdfe KBv9gMW6kEXdtXGdUo8NcMQlvuUsT+ukNeGF5YUI3+sAj1Q2tZEpkAThQZ+WnGoLedPL kYg1n2fWwzqsQeDYPoHrxI6pbPruO1Ala8EXCNh9TvXnB6OdNHD+znsaTd/Tu4d4QHEZ Sx/HLq8gaiLHxqBhubEVh0jWI18rY+qFFE9XCd6aTopm69br/ekwMljcY5V6WISaW++5 jhsm/ff/eEPlTuK2RiyeLW1bhSv/0Bx1KPH0T5YZoOSEOd18EzgWE+8CcDW/5lFoeSKL oQ== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2120.oracle.com with ESMTP id 2mc6cpmfxm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 11 Sep 2018 14:13:31 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w8BEDPFf026013 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 11 Sep 2018 14:13:25 GMT Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w8BEDPtZ027774; Tue, 11 Sep 2018 14:13:25 GMT Received: from [10.191.3.83] (/10.191.3.83) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 11 Sep 2018 07:13:25 -0700 Subject: Re: [PATCH] percpu-refcount: relax limit on percpu_ref_reinit() To: Tejun Heo Cc: Ming Lei , linux-kernel@vger.kernel.org, Kent Overstreet , linux-block@vger.kernel.org References: <20180909125824.9150-1-ming.lei@redhat.com> <20180910161135.GA27430@ming.t460p> <20180911040323.GC30977@ming.t460p> <771fa1eb-85d3-2ff2-6070-207874da85b6@oracle.com> <20180911134404.GF1100574@devbig004.ftw2.facebook.com> From: "jianchao.wang" Message-ID: Date: Tue, 11 Sep 2018 22:13:23 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180911134404.GF1100574@devbig004.ftw2.facebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9012 signatures=668708 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=630 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809110145 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi tejun On 09/11/2018 09:44 PM, Tejun Heo wrote: > Hello, > > On Tue, Sep 11, 2018 at 12:40:36PM +0800, jianchao.wang wrote: >> (long)(sum (every cpu's refcounter)) + atomic refcounter >> >> and when switch to atomic mode, there could be value left in atomic refcounter. >> then the unsigned long percpu refcounter cound be decreased from 0. > > It can always do that. Imagine a task getting a ref on one cpu, > migrating and putting it on another. The only thing which matters is > that the sum of everything adds upto what it should be. > Thanks for your kindly response. I have got the point here. Thanks Jianchao