From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751432AbcBOTk2 (ORCPT ); Mon, 15 Feb 2016 14:40:28 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:55773 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbcBOTk0 (ORCPT ); Mon, 15 Feb 2016 14:40:26 -0500 Subject: Re: Crashes in arm qemu emulations due to 'cpufreq: governor: Replace timers with utilization ...' To: Tony Lindgren , "Rafael J. Wysocki" References: <20160215170527.GA24453@roeck-us.net> <20160215190116.GX19432@atomide.com> Cc: Viresh Kumar , "linux-pm@vger.kernel.org" , Peter Zijlstra , "Rafael J. Wysocki" , Linux Kernel Mailing List , linux-next@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" From: Guenter Roeck Message-ID: <56C229A5.8020901@roeck-us.net> Date: Mon, 15 Feb 2016 11:40:21 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160215190116.GX19432@atomide.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/15/2016 11:01 AM, Tony Lindgren wrote: > * Rafael J. Wysocki [160215 10:44]: >> On Mon, Feb 15, 2016 at 6:05 PM, Guenter Roeck wrote: >>> Rafael, >> >> Hi, >> >> Thanks for the report! >> >>> I see crashes in various arm qemu tests due to 'cpufreq: governor: Replace >>> timers with utilization update callbacks' with next-20160215. An example >>> crash log and bisect results are attached below. >>> >>> Please let me know if there is anything I can do to help tracking down >>> the problem. >> >> It looks like we've uncovered some nastiness in the arch ARM code (see below). >> >> [cut] >> >>> [ 1.340000] Unable to handle kernel NULL pointer dereference at virtual address 00000000 >>> [ 1.340000] pgd = c0204000 >>> [ 1.340000] [00000000] *pgd=00000000 >>> [ 1.340000] Internal error: Oops: 80000005 [#1] SMP ARM >>> [ 1.340000] Modules linked in: >>> [ 1.340000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.5.0-rc4-next-20160215 #1 >>> [ 1.340000] Hardware name: Generic OMAP3-GP (Flattened Device Tree) >>> [ 1.340000] task: cb060000 ti: cb05a000 task.ti: cb05a000 >>> [ 1.340000] PC is at 0x0 >>> [ 1.340000] LR is at arch_send_call_function_single_ipi+0x34/0x38 >> >> Since this is ARM, arch_send_call_function_single_ipi() looks like this: >> >> void arch_send_call_function_single_ipi(int cpu) >> { >> smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE); >> } >> >> so I'm not sure how the NULL pointer deref is possible even. >> >> The only thing coming to mind would be that cpumask_of(cpu) triggers >> this, but I'm not sure how exactly that can happen. >> >> I need help from somebody who knows how this low-level stuff works on ARM. > > That's not even an SMP machine? I suspect a bunch of out of the > 65 boot failures here are related to this: > > https://kernelci.org/boot/all/job/next/kernel/next-20160215/ > > The SMP ones seem to fail with some regulator issues? > There is another problem, introduced with 6a0712f6f199e ("PM / OPP: Add dev_pm_opp_set_rate()"). The kernelci boot log for next-20160212:omap3-overo-tobi and others experience that problem. Essentially, the code now assumes that a CPU clock always has a voltage regulator attached to it, which is not correct. I sent out a patch to fix that problem a minute ago. Guenter