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=-4.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 ED23EC43441 for ; Thu, 22 Nov 2018 11:05:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ABEBF20866 for ; Thu, 22 Nov 2018 11:05:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="zP3HATwJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ABEBF20866 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org 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 S2394512AbeKVVoc (ORCPT ); Thu, 22 Nov 2018 16:44:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:42012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388478AbeKVVob (ORCPT ); Thu, 22 Nov 2018 16:44:31 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C949B20820; Thu, 22 Nov 2018 11:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542884737; bh=NEl5SfX9wQ5A50uQSuYsdNM2UBgxb0nU8m4gfyAu8R4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=zP3HATwJbcT4PSLL1i143eyjWYfWVyMSn1Cikx2JAqx92BgcO8+EhNFDQ/+4XqPPv GgMrdCJ1RxkBEmwz0+1c+HzdfVu2XTDDkdElthoHaQ678cL1WW8oqsnyiOT+gODoo3 bCTsvHl/Ai0jI1F++vdJgEYm1tTes79QnL/3glP0= Date: Thu, 22 Nov 2018 12:05:34 +0100 From: Greg Kroah-Hartman To: Gao Xiang Cc: devel@driverdev.osuosl.org, linux-erofs@lists.ozlabs.org, Chao Yu , LKML , weidu.du@huawei.com, Miao Xie Subject: Re: [PATCH 04/10] staging: erofs: fix `erofs_workgroup_{try_to_freeze, unfreeze}' Message-ID: <20181122110534.GD5287@kroah.com> References: <20181120143425.43637-1-gaoxiang25@huawei.com> <20181120143425.43637-5-gaoxiang25@huawei.com> <20181122102155.GE3189@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 22, 2018 at 06:29:34PM +0800, Gao Xiang wrote: > Hi Greg, > > On 2018/11/22 18:21, Greg Kroah-Hartman wrote: > > On Tue, Nov 20, 2018 at 10:34:19PM +0800, Gao Xiang wrote: > >> There are two minor issues in the current freeze interface: > >> > >> 1) Freeze interfaces have not related with CONFIG_DEBUG_SPINLOCK, > >> therefore fix the incorrect conditions; > >> > >> 2) For SMP platforms, it should also disable preemption before > >> doing atomic_cmpxchg in case that some high priority tasks > >> preempt between atomic_cmpxchg and disable_preempt, then spin > >> on the locked refcount later. > > > > spinning on a refcount implies that you are trying to do your own type > > of locking. Why not use the in-kernel locking api instead? It will > > always do better than trying to do your own logic as the developers > > there know locking across all types of cpus better than filesystem > > developers :) > > It is because refcount also plays a role as a spinlock on a specific value > (== EROFS_LOCKED_MAGIC), no need to introduce such a value since the spin > window is small. As I said in another email, doing two things with one variable is odd as those are two different types of functions. greg k-h