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=-16.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 F08C6C433E6 for ; Tue, 1 Sep 2020 16:27:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D07FA208CA for ; Tue, 1 Sep 2020 16:27:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598977654; bh=v3ubAj4K8yP34BRJWBT76VmMtHRcJqZ7TClZ7Gyqd4k=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=MDRILAu7mv8Q4rEhh7/Q6uN7UH+MejLGxf5N7Uur8pjXOF9R/4y9pFi6Ev01cpHok cSkcbl+rJ29u4WjRGcNBaZXDXtd3V17sA0/4AIzvPbdnSoRT/s7dpfU+A10o/cY9gX dijAGQkE4ysoylDHz7Uf5FQepjRAgXixKPog0ZyM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730922AbgIAQ1b (ORCPT ); Tue, 1 Sep 2020 12:27:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:60250 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731020AbgIAQ1U (ORCPT ); Tue, 1 Sep 2020 12:27:20 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (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 F38D1206FA; Tue, 1 Sep 2020 16:27:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598977640; bh=v3ubAj4K8yP34BRJWBT76VmMtHRcJqZ7TClZ7Gyqd4k=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=Q6HE2OGr/FVFJepUDnOmpdTMZnb1YikSFFeWlERuqMdEh3lZCIgUI92wkfPVrRCHQ hIZsU5xQD7TMqN8zhsdA3A67squHOh4loHeiupztWrDR6O0tNzmC7HHj6jgwweuTBS ePpJ8gzeuOsmgnIrjcymimF4H6J91Biv+B2z+IKI= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id CF92135226A5; Tue, 1 Sep 2020 09:27:19 -0700 (PDT) Date: Tue, 1 Sep 2020 09:27:19 -0700 From: "Paul E. McKenney" To: Rong Chen Cc: kernel test robot , Ingo Molnar , LKML , lkp@lists.01.org Subject: Re: [LKP] Re: [rcuperf] 4e88ec4a9e: UBSAN:division-overflow_in_arch/x86/include/asm/div64.h Message-ID: <20200901162719.GE29330@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200831120122.GH4299@shao2-debian> <20200831155037.GZ2855@paulmck-ThinkPad-P72> <649fd850-602f-7f0d-d286-73a8dd88ad6d@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <649fd850-602f-7f0d-d286-73a8dd88ad6d@intel.com> 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 Tue, Sep 01, 2020 at 03:03:28PM +0800, Rong Chen wrote: > > > On 8/31/20 11:50 PM, Paul E. McKenney wrote: > > On Mon, Aug 31, 2020 at 08:01:22PM +0800, kernel test robot wrote: > > > Greeting, > > > > > > FYI, we noticed the following commit (built with gcc-9): > > > > > > commit: 4e88ec4a9eb17527e640b063f79e5b875733eb53 ("rcuperf: Change rcuperf to rcuscale") > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master > > > > > > > > > in testcase: trinity > > > with following parameters: > > > > > > runtime: 300s > > > > > > test-description: Trinity is a linux system call fuzz tester. > > > test-url: http://codemonkey.org.uk/projects/trinity/ > > > > > > > > > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G > > > > > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): > > > > > > > > > +---------------------------------------------------------+------------+------------+ > > > | | 65bd77f554 | 4e88ec4a9e | > > > +---------------------------------------------------------+------------+------------+ > > > | boot_successes | 13 | 0 | > > > | boot_failures | 0 | 14 | > > > | UBSAN:division-overflow_in_arch/x86/include/asm/div64.h | 0 | 14 | > > > | error:#[##] | 0 | 14 | > > > | EIP:main_func.cold | 0 | 14 | > > > | Kernel_panic-not_syncing:Fatal_exception | 0 | 14 | > > > +---------------------------------------------------------+------------+------------+ > > > > > > > > > If you fix the issue, kindly add following tag > > > Reported-by: kernel test robot > > Does the patch below fix this for you? > > Yes, this patch can fix the issue, and nreaders was adjusted to 1: > > [    5.953645] The force parameter has not been set to 1. The Iris poweroff > handler will not be installed. > [   12.546587] rcu-ref-scale: --- Start of test:  verbose=0 shutdown=1 > holdoff=10 loops=10000 nreaders=-1 nruns=30 readdelay=0 > [   12.561495] ------------[ cut here ]------------ > [   12.562016] ref_scale_init: nreaders = 0, adjusted to 1 > [   12.562601] WARNING: CPU: 0 PID: 1 at kernel/rcu/refscale.c:684 > ref_scale_init+0x653/0x80 Thank you! May I add your Tested-by? Thanx, Paul > Best Regards, > Rong Chen > > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit d301e320e952e2e604d83d9540e52510b0eb3d94 > > Author: Paul E. McKenney > > Date: Thu Aug 27 09:58:19 2020 -0700 > > > > refscale: Bounds-check module parameters > > The default value for refscale.nreaders is -1, which results in the code > > setting the value to three-quarters of the number of CPUs. On single-CPU > > systems, this results in three-quarters of the value one, which the C > > language's integer arithmetic rounds to zero. This in turn results in > > a divide-by-zero error. > > This commit therefore adds bounds checking to the refscale module > > parameters, so that if they are less than one, they are set to the > > value one. > > Reported-by: kernel test robot > > Signed-off-by: Paul E. McKenney > > > > diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c > > index 952595c..fb5f20d 100644 > > --- a/kernel/rcu/refscale.c > > +++ b/kernel/rcu/refscale.c > > @@ -681,6 +681,12 @@ ref_scale_init(void) > > // Reader tasks (default to ~75% of online CPUs). > > if (nreaders < 0) > > nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2); > > + if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops)) > > + loops = 1; > > + if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders)) > > + nreaders = 1; > > + if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns)) > > + nruns = 1; > > reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]), > > GFP_KERNEL); > > if (!reader_tasks) { > > _______________________________________________ > > LKP mailing list -- lkp@lists.01.org > > To unsubscribe send an email to lkp-leave@lists.01.org >