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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 8D19AC433E0 for ; Fri, 29 May 2020 13:55:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E90E206A4 for ; Fri, 29 May 2020 13:55:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590760559; bh=Enq4Wi87oreGuApmcECdC9lGbckzzO7dttk0SumdA8I=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=FSJ1ao5uVtOZVRPM3Bvi4NTgewS2bACbImusgagYTl7sQxTtm6lt6NaRM/bo1EyGK P/XExM4zBumbUgyBQB2Irmavzng5XHPfG47a33RbioPApwXTntGHrPEDDdc+A+AdpK LhTc1X7phxV9V6qjO8dKabXhN6eE/MqU4hpFrihI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727035AbgE2Nz6 (ORCPT ); Fri, 29 May 2020 09:55:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:42182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbgE2Nz4 (ORCPT ); Fri, 29 May 2020 09:55:56 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2FEAF206A1; Fri, 29 May 2020 13:55:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590760556; bh=Enq4Wi87oreGuApmcECdC9lGbckzzO7dttk0SumdA8I=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=y+vhlNBOERjmS74ytjDE/P3H+GHEsVKlAPSoz794yexAFW2fIJ8C4+hC/l5dMVUO5 eeuabMM1Jvn7XY2oJnBNU+WUW5XCBf12jzL6bQHdkv6PP0HGmzvq1xojIYHq8mandh 9FCrsbDJSwxS/0a4hWdnd+kECgtF2rnkg4XCqO0Q= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 152923522683; Fri, 29 May 2020 06:55:56 -0700 (PDT) Date: Fri, 29 May 2020 06:55:56 -0700 From: "Paul E. McKenney" To: Valdis =?utf-8?Q?Kl=C4=93tnieks?= Cc: Josh Triplett , Steven Rostedt , rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: next-20200528 - build error in kernel/rcu/refperf.c Message-ID: <20200529135556.GY2869@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <538911.1590725791@turing-police> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <538911.1590725791@turing-police> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2020 at 12:16:31AM -0400, Valdis Klētnieks wrote: > commit 9088b449814f788d24f35a5840b6b2c2a23cd32a > Author: Paul E. McKenney > Date: Mon May 25 17:22:24 2020 -0700 > > refperf: Provide module parameter to specify number of experiments > > changes this line of code (line 389) > > - reader_tasks[exp].result_avg = 1000 * process_durations(exp) / ((exp + 1) * loops); > + result_avg[exp] = 1000 * process_durations(nreaders) / (nreaders * loops); > > On a 32-bit ARM make allmodconfig with gcc 8.3, this results in: > > ERROR: modpost: "__aeabi_uldivmod" [kernel/rcu/refperf.ko] undefined! > make[1]: *** [scripts/Makefile.modpost:103: __modpost] Error 1 > > I admit not understanding why the original line of code worked and the new one doesn't. > Maybe gcc is smarter/dumber about the ranges of 'exp' and 'nreaders' than we thought? I was surprised by that as well, but yesterday I took the lazy way out by making this module depend on 64BIT. (0day reported a similar issue on m68k.) So this issue should no longer show up. ;-) Thanx, Paul