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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 B35CEC432C0 for ; Thu, 21 Nov 2019 20:20:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8871920672 for ; Thu, 21 Nov 2019 20:20:08 +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="QKqJyLmM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727107AbfKUUUH (ORCPT ); Thu, 21 Nov 2019 15:20:07 -0500 Received: from merlin.infradead.org ([205.233.59.134]:58896 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbfKUUUG (ORCPT ); Thu, 21 Nov 2019 15:20:06 -0500 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=qOktCdLLVB7nTmJcxwH9iwxLQvm6tnAzKuSohvP2NxY=; b=QKqJyLmM0ryi+pVTsX9E5xBDo 1LT0g4qnkID9F1BatrY2Fz0Kcu9yWX72F6OGoAmH2zebp/uh9sBEY4AZCOC89AB64baY+GxFV28Jn bELXaEPnDl0G9RI/iq8xeOVyUReRHZ4hCdqB7cZsi219jx4Qy9U+DbkZfZKlYxTjE6Xzx/QCmtMFP 5jfbOIL4yvZUlW3q99MxBFAwm/di7EVk1AJsOz5/vbLc19jBUZnRWhrqqiiIAGeeClSa4wqJt4cth JWjx6oaz8wR987r13sC3BYbcJNlrP4bfCeFCDkVeyAetAPEtUyAXFIB0qIiNf8m5a0vw8E2PWEXJF 7+PTGMpFQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iXsvh-0000l2-QH; Thu, 21 Nov 2019 20:19:53 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1EF1E300606; Thu, 21 Nov 2019 21:18:40 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1D64A201F87D3; Thu, 21 Nov 2019 21:19:51 +0100 (CET) Date: Thu, 21 Nov 2019 21:19:51 +0100 From: Peter Zijlstra To: Fenghua Yu Cc: Andy Lutomirski , Andy Lutomirski , David Laight , Ingo Molnar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Tony Luck , Ashok Raj , Ravi V Shankar , linux-kernel , x86 Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Message-ID: <20191121201951.GY4097@hirez.programming.kicks-ass.net> References: <20191121185303.GB199273@romley-ivt3.sc.intel.com> <4BB1CB74-887B-4F40-B3B2-F0147B264C34@amacapital.net> <20191121202535.GC199273@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191121202535.GC199273@romley-ivt3.sc.intel.com> 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 21, 2019 at 12:25:35PM -0800, Fenghua Yu wrote: > > > We are working on a separate patch set to fix all split lock issues > > > in atomic bitops. Per Peter Anvin and Tony Luck suggestions: > > > 1. Still keep the byte optimization if nr is constant. No split lock. > > > 2. If type of *addr is unsigned long, do quadword atomic instruction > > > on addr. No split lock. > > > 3. If type of *addr is unsigned int, do word atomic instruction > > > on addr. No split lock. > > > 4. Otherwise, re-calculate addr to point the 32-bit address which contains > > > the bit and operate on the bit. No split lock. > Actually we only find 8 places calling atomic bitops using type casting > "unsigned long *". After above changes, other 8 patches remove the type > castings and then split lock free in atomic bitops in the current kernel. Those above changes are never going to happen.