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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 760E1C433F1 for ; Tue, 14 Jul 2020 09:01:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 461D62145D for ; Tue, 14 Jul 2020 09:01:48 +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="RLz9MrfH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726789AbgGNJBr (ORCPT ); Tue, 14 Jul 2020 05:01:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbgGNJBq (ORCPT ); Tue, 14 Jul 2020 05:01:46 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95BDEC061755; Tue, 14 Jul 2020 02:01:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=IEtrkLlps7g52f3KP4zftkc/KLK6f+C0uXLbsSjl3uQ=; b=RLz9MrfHLmONZpFpC3K3FlC3Fr TPk0T+JjqliICOmcZq8FaHFbIpxjaj7Zj5MvC5z3HSM04AcgptnCTRFzNrJkzySwPvuXi8jg2BSwM mIkcy6wD0cBETlP/w8NhrPb0+MqJm90qMZfumCkLb+vN4qWg5tDt1N3Q6s/qDOlPyWxuOvpi254wk RqXLOzAshCSOT04yao6ZNjhgkfu3fY82YQ//zG/W2kRfYPH2jhT/2iCikeZiG4xQlEQD+9sg72Nm5 fzMKLwMrofbyCWOE/m+0XojzSDjLh7EUMIY7LQQuLInA7YX7U6raXqcUkQ7MUKJpPohSaLpqnDXxh CEKyTQ3A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvGob-00014B-6s; Tue, 14 Jul 2020 09:01:29 +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 A43CF305C22; Tue, 14 Jul 2020 11:01:26 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 86E1628B91075; Tue, 14 Jul 2020 11:01:26 +0200 (CEST) Date: Tue, 14 Jul 2020 11:01:26 +0200 From: Peter Zijlstra To: Waiman Long Cc: Nicholas Piggin , Arnd Bergmann , Borislav Petkov , Davidlohr Bueso , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Will Deacon , x86@kernel.org Subject: Re: [PATCH 2/2] locking/pvqspinlock: Optionally store lock holder cpu into lock Message-ID: <20200714090126.GR10769@hirez.programming.kicks-ass.net> References: <20200711182128.29130-1-longman@redhat.com> <20200711182128.29130-3-longman@redhat.com> <20200712173452.GB10769@hirez.programming.kicks-ass.net> <1594613637.ds7pt1by9l.astroid@bobo.none> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 13, 2020 at 10:48:00PM -0400, Waiman Long wrote: > Storing the cpu number into the lock can be useful for other reason too. It > is not totally related to PPC support. Well, the thing you did only works for 'small' (<253 CPU) systems. There's a number of Power systems that's distinctly larger than that. So it simply cannot work as anything other than a suggestion/hint. It must not be a correctness thing.