From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932535AbdA3Qg4 (ORCPT ); Mon, 30 Jan 2017 11:36:56 -0500 Received: from mail-qk0-f193.google.com ([209.85.220.193]:34076 "EHLO mail-qk0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932508AbdA3Qgi (ORCPT ); Mon, 30 Jan 2017 11:36:38 -0500 Subject: Re: [PATCH] perf/x86/intel/rapl: Rename rapl_cpu_prepare() to rapl_cpu_starting() To: Thomas Gleixner References: <9063c543-880e-0b12-0671-1492182990e7@gmail.com> Cc: linux-kernel@vger.kernel.org, x86@kernel.org From: Yasuaki Ishimatsu Message-ID: <8722b425-4f20-20e5-7828-3feb0a3c4109@gmail.com> Date: Mon, 30 Jan 2017 11:36:53 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, Do you have any idea to fix the issue? If you have the idea, please send me the patch. Thanks, Yasuaki Ishimatsu On 01/24/2017 02:54 PM, Thomas Gleixner wrote: > On Tue, 24 Jan 2017, Yasuaki Ishimatsu wrote: >> rapl_cpu_prepare() must be called after logical package id of CPU >> is set by topology_update_package_map(). >> >> But when onlining hot-added CPU, rapl_cpu_prepare() is called before >> setting logical package id of the hot-added CPU. So cpu_to_rapl_pmu() >> in rapl_cpu_prepare() finds a rapl_pmu of wrong logical package id and >> rapl_cpu_prepare() initializes the wrong rapl_pmu. >> >> After that logical package id of the hot-added CPU is set by >> topology_update_package_map(). But rapl_cpu_prepare() does >> not initialize pmu of the logical package id of the hot-added CPU. >> So when calling rapl_cpu_online(), cpu_to_rapl_pmu() returns NULL and >> the following NULL pointer dereference occurs. >> >> BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 >> IP: rapl_cpu_online+0x8d/0xb0 >> >> Call Trace: >> ? rapl_cpu_offline+0xc0/0xc0 >> cpuhp_invoke_callback+0x8d/0x3f0 >> cpuhp_up_callbacks+0x37/0xb0 >> cpuhp_thread_fun+0xc9/0xe0 >> smpboot_thread_fn+0x110/0x160 >> kthread+0x101/0x140 >> ? sort_range+0x30/0x30 >> ? kthread_park+0x90/0x90 >> ret_from_fork+0x25/0x30 >> >> The patch renames rapl_cpu_prepare() to rapl_cpu_starting() and changes >> the position of cpuhp_state so that rapl_cpu_starting() is called >> after topology_update_package_map(). > > Does not work. You cannot call that callback in the starting context. It > does allocations. This needs be fixed in a different way. I'll have a look > tomorrow. > > Thanks, > > tglx >