Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756659AbcKBWsQ (ORCPT ); Wed, 2 Nov 2016 18:48:16 -0400 Received: from mx0a-000f0801.pphosted.com ([67.231.144.122]:48613 "EHLO mx0a-000f0801.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755768AbcKBWsP (ORCPT ); Wed, 2 Nov 2016 18:48:15 -0400 Subject: Re: [RFC PATCH] perf/x86/intel/rapl: avoid access unallocate memory To: Sebastian Andrzej Siewior , References: <20161102122557.qs4rl6mb7n7l7j7p@linutronix.de> CC: , "M. Vefa Bicakci" From: "Charles (Chas) Williams" Message-ID: <24e69019-60d0-29e7-e31f-c6f00f9ed98a@brocade.com> Date: Wed, 2 Nov 2016 18:47:49 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.3.0 MIME-Version: 1.0 In-Reply-To: <20161102122557.qs4rl6mb7n7l7j7p@linutronix.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: hq1wp-excas14.corp.brocade.com (10.70.38.103) To BRMWP-EXMB12.corp.brocade.com (172.16.59.130) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-11-02_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1611020407 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1345 Lines: 31 On 11/02/2016 08:25 AM, Sebastian Andrzej Siewior wrote: > I am not sure if this a race with the new hotplug code or something that was > always there. Both (M. Vefa Bicakc and Charles) say that the box boots > sometimes fine (without the patch). smp_store_boot_cpu_info() should have run > before the notofoert and thus should have set the info properly. However I got > the following bootlog from Charles with this patch: I don't this this is a race. Here is some debugging from the two CPU VM (2 sockets, 1 core per socket). In identify_cpu() we have: /* The boot/hotplug time assigment got cleared, restore it */ c->logical_proc_id = topology_phys_to_logical_pkg(c->phys_proc_id); The values just after this: [ 0.228306] identify_cpu: c ffff88023fd0a040 logical_proc_id 65535 c->phys_proc_id 2 So what's interesting here, is the phys_proc_id of 2 for CPU1: int topology_phys_to_logical_pkg(unsigned int phys_pkg) { if (phys_pkg >= max_physical_pkg_id) return -1; return physical_to_logical_pkg[phys_pkg]; } And we happen to know the max_physical_pkg_id is 2 in this case. So apparently, topology_phys_to_logical_pkg() returns -1 and it gets assigned to the logical_proc_id. I don't know why the CPU's phys_proc_id is 2.