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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 35245C3279B for ; Fri, 6 Jul 2018 12:05:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8F9023FCF for ; Fri, 6 Jul 2018 12:05:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IGx7aCyt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8F9023FCF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.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 S932816AbeGFMFp (ORCPT ); Fri, 6 Jul 2018 08:05:45 -0400 Received: from merlin.infradead.org ([205.233.59.134]:43836 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753672AbeGFMFo (ORCPT ); Fri, 6 Jul 2018 08:05:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3g9h+VMg1o12oa5nA8Cpbglt+dSX1GSsGn7A6f2NYNs=; b=IGx7aCytwz3fbMMNU1GQL64sr Q1pYKHhnyRlJpya3lPqF3zQZV3HvOVqR2LwIBjN5PRT3QLX2sr1TaMn8PoxIzQ0eqAx2SVMihNcA7 JnncZhjcH2IyBPt+XI4CDVvS68S+HpJxXv9701fKHJbGMZsRryCizoqb/QTwWGj7dX8CiKvlobSGP AQBmvB0DMBXCTorJHriTub0uhZMyoz6uLz4PZoGYmD6L5/tUTCcGsfM7UULjS6lmUssCORW9zY3DL t8BLMPJDQa7cLpz9rgG8p21kFbxxABtJMEKle/rubN3d0Sb53m7wUOtEo57B+Fm0/vu4eV4HkJBVi tTESHFbUA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fbPUU-0000l7-7f; Fri, 06 Jul 2018 12:05:35 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0029D20289CE4; Fri, 6 Jul 2018 14:05:32 +0200 (CEST) Date: Fri, 6 Jul 2018 14:05:32 +0200 From: Peter Zijlstra To: Guo Ren 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: <20180706120532.GX2476@hirez.programming.kicks-ass.net> References: <860b8db036b33d7b3648cb1f4ec827a53dc1a01b.1530465326.git.ren_guo@c-sky.com> <20180705180008.GG2530@hirez.programming.kicks-ass.net> <20180706114812.GC27148@guoren> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180706114812.GC27148@guoren> User-Agent: Mutt/1.10.0 (2018-05-17) 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 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.