From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754481Ab1JBTue (ORCPT ); Sun, 2 Oct 2011 15:50:34 -0400 Received: from mail-pz0-f42.google.com ([209.85.210.42]:53947 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753794Ab1JBTu2 (ORCPT ); Sun, 2 Oct 2011 15:50:28 -0400 Date: Sun, 2 Oct 2011 12:50:23 -0700 From: Tejun Heo To: "Srivatsa S. Bhat" Cc: "Rafael J. Wysocki" , tigran@aivazian.fsnet.co.uk, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, Linux PM mailing list Subject: Re: [BUGFIX][PATCH] Freezer, CPU hotplug, x86 Microcode: Fix task freezing failures Message-ID: <20111002195023.GC31799@mtj.dyndns.org> References: <4E88B5E0.6080503@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E88B5E0.6080503@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Oct 03, 2011 at 12:35:04AM +0530, Srivatsa S. Bhat wrote: > So, this patch addresses this issue by ensuring that microcode is not freed > from kernel memory, nor invalidated when a CPU goes offline. Thus once the > kernel gets the microcode during boot-up, it will never have to depend on > userspace ever again to get microcode, since it never releases the copy it > already has. So every run of the microcode callback for CPU online event will > now succeed irrespective of whether userspace is frozen or not. As a result, > this fixes the task freezing failure encountered while running CPU hotplug > stress test along with suspend/resume operations simultaneously. I'm not familiar with how microcode is supposed to be managed but is it impossible for the newly hotplugged CPU (an actual hot unplug / plug) may not like the microcode loaded for the previous CPU? Isn't that why CPU_DEAD was invalidating the microcode? Thanks. -- tejun