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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,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 7C442C3279B for ; Fri, 6 Jul 2018 13:46:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33EEB21C39 for ; Fri, 6 Jul 2018 13:46:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 33EEB21C39 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.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 S1753905AbeGFNqx (ORCPT ); Fri, 6 Jul 2018 09:46:53 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:57657 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753605AbeGFNqw (ORCPT ); Fri, 6 Jul 2018 09:46:52 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.08599114|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e01e01542;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=12;RT=12;SR=0;TI=SMTPD_---.CN6DRWy_1530884776; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.CN6DRWy_1530884776) by smtp.aliyun-inc.com(10.147.44.145); Fri, 06 Jul 2018 21:46:16 +0800 Date: Fri, 6 Jul 2018 21:46:16 +0800 From: Guo Ren To: Peter Zijlstra Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com Subject: Re: [PATCH V2 11/19] csky: Atomic operations Message-ID: <20180706134616.GA25190@guoren> References: <860b8db036b33d7b3648cb1f4ec827a53dc1a01b.1530465326.git.ren_guo@c-sky.com> <20180705180008.GG2530@hirez.programming.kicks-ass.net> <20180706114812.GC27148@guoren> <20180706120532.GX2476@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180706120532.GX2476@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 06, 2018 at 02:05:32PM +0200, Peter Zijlstra wrote: > On Fri, Jul 06, 2018 at 07:48:12PM +0800, Guo Ren wrote: > > On Thu, Jul 05, 2018 at 08:00:08PM +0200, Peter Zijlstra wrote: > > > On Mon, Jul 02, 2018 at 01:30:14AM +0800, Guo Ren wrote: > > > > +#ifdef CONFIG_CPU_HAS_LDSTEX > > > > +ENTRY(csky_cmpxchg) > > > > + USPTOKSP > > > > + mfcr a3, epc > > > > + INCTRAP a3 > > > > + > > > > + subi sp, 8 > > > > + stw a3, (sp, 0) > > > > + mfcr a3, epsr > > > > + stw a3, (sp, 4) > > > > + > > > > + psrset ee > > > > +1: > > > > + ldex a3, (a2) > > > > + cmpne a0, a3 > > > > + bt16 2f > > > > + mov a3, a1 > > > > + stex a3, (a2) > > > > + bez a3, 1b > > > > +2: > > > > + sync.is > > > > + mvc a0 > > > > + ldw a3, (sp, 0) > > > > + mtcr a3, epc > > > > + ldw a3, (sp, 4) > > > > + mtcr a3, epsr > > > > + addi sp, 8 > > > > + KSPTOUSP > > > > + rte > > > > +END(csky_cmpxchg) > > > > +#else > > > > > > Please explain... if the CPU has LDEX/STEX, then _why_ do you need this? > > Our libc use csky_cmpxchg and we want it compatible. Of course, we'll > > also implement the ldex/stex atomic operations in libs in future. > > I would strongly suggest not providing this syscall on SMP systems from > the get go. There is no point in starting with legacy problems without > an actual legacy. Ok.