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 9E95FC433DF for ; Fri, 29 May 2020 14:02:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CB122073B for ; Fri, 29 May 2020 14:02:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590760950; bh=jboWdieI7iFp1rpneZBaX90NHx5TQzh4MghY5RexMJE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=Wr75erGBWjs+DtzR6wG1FOSkJQPCzND12/ZCKMW8P22U9lvYPAamxEbidpP6pQRVS d7Mf/0Oldci4854T4pocuSOIjRiN4SSNf6OLAc12p1jmrNiNZ64a6DG8YrXE6NAvWr Tk96WAi8My5Peu4JUr1/NyKPZmYJoqQzMVciCRZE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726903AbgE2OC3 (ORCPT ); Fri, 29 May 2020 10:02:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:44656 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbgE2OC3 (ORCPT ); Fri, 29 May 2020 10:02:29 -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 EBBC620707; Fri, 29 May 2020 14:02:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590760949; bh=jboWdieI7iFp1rpneZBaX90NHx5TQzh4MghY5RexMJE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=AwerKJm7rYuen+5zU+J2jkZzKnPY1dzfpRGir1cVzkNId9Cf5o1CZKeP95vv3++Gr rq02zr9oxYbVdIRUeWe7pkX7b5nmrv0dcj6RDgVFF/mqHAY0bYG8mGZghGpHlEPkJQ OTqMNjbeiZJ2PHNELZxMjVhzHO6AyfSmFUmUFhjM= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C62183522683; Fri, 29 May 2020 07:02:28 -0700 (PDT) Date: Fri, 29 May 2020 07:02:28 -0700 From: "Paul E. McKenney" To: Valdis =?utf-8?Q?Kl=C4=93tnieks?= Cc: Randy Dunlap , 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: <20200529140228.GZ2869@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <538911.1590725791@turing-police> <9d8b13db-9d77-416d-e283-9ea509ce43d1@infradead.org> <543040.1590729879@turing-police> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <543040.1590729879@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 01:24:39AM -0400, Valdis Klētnieks wrote: > On Thu, 28 May 2020 21:48:18 -0700, Randy Dunlap said: > > > > ERROR: modpost: "__aeabi_uldivmod" [kernel/rcu/refperf.ko] undefined! > > Gaah. And the reason I didn't spot Paul's post while grepping my linux-kernel > mailbox is because *that* thread had a different undefined reference: > > > > > > > > m68k-linux-ld: kernel/rcu/refperf.o: in function `main_func': > > > > > > > >> refperf.c:(.text+0x762): undefined reference to `__umoddi3' > > > Paul has already responded: (unfortunately) > > > > "So I am restricting to 64BIT for the time being. Yeah, I know, lazy of > > me. ;-)" > > It's the sort of issue that's well into "as long as it gets mostly fixed before > it hits Linus's tree" territory. I've seen lots of far worse work-arounds in > the years since the 2.5.47 kernel. :) Fair enough! Also as noted on the other thread, in this case, doing this 64-bit division the hard way shouldn't be a problem: The performance test is finished and nothing else is happening. So I have to wonder whether it would be possible to detect this based on some sort of link-time checking, presumably in conjunction with -O0 to avoid confusing the whitelist with compiler optimizations. That would allow use of C-language "/" and "%" while still allowing gratuitous uses to be questioned. Hey, I can dream, can't I? ;-) Thanx, Paul