From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754614Ab2IXLwo (ORCPT ); Mon, 24 Sep 2012 07:52:44 -0400 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:42666 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754302Ab2IXLwk (ORCPT ); Mon, 24 Sep 2012 07:52:40 -0400 Message-ID: <50604941.9050806@linux.vnet.ibm.com> Date: Mon, 24 Sep 2012 17:21:29 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Fengguang Wu CC: Borislav Petkov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Peter Zijlstra , Andrew Morton , Johannes Weiner , Conny Seidel , "Paul E. McKenney" Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e References: <20120924102324.GA22303@aftab.osrc.amd.com> <50603829.9050904@linux.vnet.ibm.com> <20120924110554.GC22303@aftab.osrc.amd.com> <50604047.7000908@linux.vnet.ibm.com> <20120924113447.GA25182@localhost> In-Reply-To: <20120924113447.GA25182@localhost> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12092411-8878-0000-0000-0000041E9782 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2012 05:04 PM, Fengguang Wu wrote: > On Mon, Sep 24, 2012 at 04:43:11PM +0530, Srivatsa S. Bhat wrote: >> On 09/24/2012 04:35 PM, Borislav Petkov wrote: >>> On Mon, Sep 24, 2012 at 04:08:33PM +0530, Srivatsa S. Bhat wrote: >>>> On 09/24/2012 03:53 PM, Borislav Petkov wrote: >>>>> Hi all, >>>>> >>>>> we're able to trigger the oops below when doing CPU hotplug tests. >>>>> >>>> >>>> I hit this problem as well, which I reported here, a few days ago: >>>> https://lkml.org/lkml/2012/9/13/222 >>> >>> Ok, your case shows even more info: >>> >>> [ 526.024180] divide error: 0000 [#1] SMP >>> [ 526.028144] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm cdc_ether pcspkr usbnet shpchp pci_hotplug i2c_i801 i2c_core ioatdma mii crc32c_intel serio_raw microcode lpc_ich mfd_core i7core_edac bnx2 dca edac_core tpm_tis tpm sg tpm_bios rtc_cmos button uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon >>> [ 526.028145] CPU 9 >>> [ 526.028145] Pid: 2235, comm: flush-8:0 Not tainted 3.6.0-rc1-tglx-hotplug-0.0.0.28.36b5ec9-default #1 IBM IBM System x -[7870C4Q]-/68Y8033 >>> [ 526.028145] RIP: 0010:[] [] bdi_dirty_limit+0x66/0xc0 >>> [ 526.028145] RSP: 0018:ffff8811530bfcc0 EFLAGS: 00010206 >>> [ 526.028145] RAX: 0000000000b9877e RBX: 00000000001a8112 RCX: 28f5c28f5c28f5c3 >>> [ 526.028145] RDX: 0000000000000000 RSI: 0000000000b9877e RDI: 0000000000000000 >>> >>> %rax contains something != 0 but %rdi definitely is 0. >>> >> >> Yep.. So I tried putting a BUG_ON(!den) in fprop_fraction_percpu() to >> catch if we really got the code wrong somehow.. but unfortunately, with >> that added, I haven't been successful in reproducing the bug :( > > Will you test such a line? At least the generic do_div() only uses the > lower 32bits for division. > > WARN_ON(!(den & 0xffffffff)); > Sure, I'll test this and report back. Thanks for the suggestion! Regards, Srivatsa S. Bhat