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, 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 3895FC3279B for ; Fri, 6 Jul 2018 12:03:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC90223FC1 for ; Fri, 6 Jul 2018 12:03:56 +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="GWE4tLEL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DC90223FC1 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 S932648AbeGFMDw (ORCPT ); Fri, 6 Jul 2018 08:03:52 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52400 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932343AbeGFMDt (ORCPT ); Fri, 6 Jul 2018 08:03:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=Kb666mxKH0l5bKQzR87zVDr/XVF5EUlLiJcDEk2F938=; b=GWE4tLEL+0kKGesWheDf2egXQ QjQEkC0UoCER7egdk/WAktrVbyebEutZ960PiHiDRJeI6yWKBHV6fsEehVOf73XcGlsd1HrpK7EyW Mz3fzYazemhLXCSCk5kyWbK1vFrT/DnHQUVJ0V+uac0iCRWgPVtWGHRj/U6hawZZ6CwkjZCMPfXfX BHklUFkSAU6N4+us2ApufTkr/vGNIbkYPgSS5gxl6AC40wVMC1KGqhcBNSDnthMYagaF08+DSaLlB 07iW/E2OrRWa5/2ea7fhZ7yRxsPHw8Xt6H2p1b39sAYVkXkMn1qLbsfbPkYFsTLKARyySmrLWVxAq 5FUNOZPCQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fbPSP-0004Or-Bp; Fri, 06 Jul 2018 12:03:25 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C39A020289CE4; Fri, 6 Jul 2018 14:03:23 +0200 (CEST) Date: Fri, 6 Jul 2018 14:03:23 +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: <20180706120323.GW2476@hirez.programming.kicks-ass.net> References: <860b8db036b33d7b3648cb1f4ec827a53dc1a01b.1530465326.git.ren_guo@c-sky.com> <20180705175902.GF2530@hirez.programming.kicks-ass.net> <20180706114402.GB27148@guoren> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180706114402.GB27148@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 07:44:03PM +0800, Guo Ren wrote: > On Thu, Jul 05, 2018 at 07:59:02PM +0200, Peter Zijlstra wrote: > > On Mon, Jul 02, 2018 at 01:30:14AM +0800, Guo Ren wrote: > > > > > +static inline void arch_spin_lock(arch_spinlock_t *lock) > > > +{ > > > + unsigned int *p = &lock->lock; > > > + unsigned int tmp; > > > + > > > + asm volatile ( > > > + "1: ldex.w %0, (%1) \n" > > > + " bnez %0, 1b \n" > > > + " movi %0, 1 \n" > > > + " stex.w %0, (%1) \n" > > > + " bez %0, 1b \n" > > > + : "=&r" (tmp) > > > + : "r"(p) > > > + : "memory"); > > > + smp_mb(); > > > +} > > > > Test-and-set with MB acting as ACQUIRE, ok. > Em ... Ok, I'll try to use test-and-set function instead of it. "test-and-set" is just the name of this type of spinlock implementation. You _could_ use the linux test_and_set bitop, but those are defined on unsigned long and spinlock_t is generally assumed to be of unsigned int size. Go with the ticket locks as per below. > > Also, the fact that you need MB for release implies your LDEX does not > > in fact imply anything and your xchg/cmpxchg implementation is broken. > xchg/cmxchg broken without 1th smp_mb()? Why we need protect the > instructions flow before the ldex.w? See the email I send earlier in that thread. > Ok, I'll try to implement ticket lock in next version patch. If you need inspiration, look at: git show 81bb5c6420635dfd058c210bd342c29c95ccd145^1:arch/arm64/include/asm/spinlock.h Or look at the current version of that file and ignore the LSE version. Note that unlock is a store half-word (u16), not having seen your arch manual yet I don't know if you even have that.