From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758836Ab2CJBwP (ORCPT ); Fri, 9 Mar 2012 20:52:15 -0500 Received: from ch1ehsobe005.messaging.microsoft.com ([216.32.181.185]:30130 "EHLO ch1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755868Ab2CJBwM (ORCPT ); Fri, 9 Mar 2012 20:52:12 -0500 X-SpamScore: -6 X-BigFish: VPS-6(z21eNzzz1202hzzz2fh668h839h) X-Forefront-Antispam-Report: CIP:160.33.98.74;KIP:(null);UIP:(null);IPV:NLI;H:mail7.fw-bc.sony.com;RD:mail7.fw-bc.sony.com;EFVD:NLI Message-ID: <4F5AB3B6.2040705@am.sony.com> Date: Fri, 9 Mar 2012 17:51:50 -0800 From: Frank Rowand Reply-To: User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: , CC: , Subject: 3.0.23-rt39 BUG: scheduling while atomic, _cpu_down() Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-OriginatorOrg: am.sony.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, (and Steve, since you've been mucking about in the hotplug code,) Yet another bit of fallout related to hotplug. This appears to affect 3.0-rt1, 3.0.23-rt29, and 3.2.9-rt17. (Thus probably all 3.x versions, but I haven't been masochistic enough to check.) If not defined CONFIG_PREEMPT_RT_FULL then - hotplug_lock() is a mutex_lock() - cpu_hotplug_begin() calls hotplug_lock() - _cpu_down() calls cpu_hotplug_begin() with preemption disabled (disabled by the migrate_disable()) The call to cpu_hotplug_begin() is not in a preempt disabled region until hotplug-use-migrate-disable.patch. This patch moves the preempt_enable() (aka migrate_enable()) from just before calling cpu_hotplug_begin() to after "out_cancel:". The BUG can be triggered by: echo 0 > /sys/devices/system/cpu/cpu1/online -Frank