From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Bohan Subject: Re: console_cpu_notify can cause scheduling BUG during CPU hotplug Date: Wed, 27 Apr 2011 15:12:19 -0700 Message-ID: <4DB894C3.2040300@codeaurora.org> References: <4DB604C7.8090305@codeaurora.org> <4DB65EEC.7060604@ti.com> <4DB733D4.3000002@codeaurora.org> <20110427073839.GA16718@liondog.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from wolverine01.qualcomm.com ([199.106.114.254]:34259 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752349Ab1D0WMU (ORCPT ); Wed, 27 Apr 2011 18:12:20 -0400 In-Reply-To: <20110427073839.GA16718@liondog.tnic> Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Borislav Petkov , Santosh Shilimkar , Kevin Cernekee , mingo@elte.hu, akpm@linux-foundation.org, simon.kagstrom@netinsight. On 4/27/2011 12:38 AM, Borislav Petkov wrote: > Great, whatever you guys come up with, we'd like to give it a run too. > We (AMD) hit the same issue in one of our tests but in our case we end > up in an endless loop of the state machine at stop_machine_cpu_stop() > since the core being offlined cannot ack the state transition to > STOPMACHINE_EXIT due to a similar reason. > > One possible fix is dropping CPU_DYING from console_cpu_notify() > since it is called into by the offlining path in > kernel/cpu.c::take_cpu_down(). This seems to be a different problem. Could you elaborate about why removing CPU_DYING from console_cpu_notify resolves your problem? What are other possible fixes? In the failure case I witnessed, we're attempting to sleep in atomic mode, which is a clear violation caused by the addition of CPU_DYING. I haven't thoroughly investigated whether other actions in console_cpu_notify (eg. ONLINE, DEAD, DOWN_FAILED, UP_CANCELED) are in atomic mode violation as well. Thanks, Mike -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum