Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934974Ab3DKILK (ORCPT ); Thu, 11 Apr 2013 04:11:10 -0400 Received: from www.linutronix.de ([62.245.132.108]:39581 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479Ab3DKILF (ORCPT ); Thu, 11 Apr 2013 04:11:05 -0400 Date: Thu, 11 Apr 2013 10:10:54 +0200 (CEST) From: Thomas Gleixner To: "Srivatsa S. Bhat" cc: Dave Hansen , Borislav Petkov , LKML , Dave Jones , dhillf@gmail.com, Peter Zijlstra , Ingo Molnar Subject: Re: [PATCH] CPU hotplug, smpboot: Fix crash in smpboot_thread_fn() In-Reply-To: <5165713D.7030503@linux.vnet.ibm.com> Message-ID: References: <515F457E.5050505@sr71.net> <515FCAC6.8090806@linux.vnet.ibm.com> <20130407095025.GA31307@pd.tnic> <20130408115553.GA4395@pd.tnic> <516439DF.3050901@sr71.net> <5165713D.7030503@linux.vnet.ibm.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1303 Lines: 30 On Wed, 10 Apr 2013, Srivatsa S. Bhat wrote: > Interestingly, in every single stack trace, the crashing task is the migration > thread. Now, migration thread belongs to the highest priority stop_task sched > class, and this particular sched class is very unique in the way it implements > its internal sched class functions, and I suspect this has a lot of bearing > on how functions like kthread_bind(), wake_up_process() etc react with it > (by looking at how it implements its functions such as select_task_rq(), > enqueue_task(), dequeue_task() etc). I don't think that's relevant. The migration thread can only be woken via try_to_wakeup and my previous patch which implements a separate task state makes sure that it cannot be woken accidentaly by anything else than unpark. > But note that __kthread_bind() can wake up the task if the task is an RT > task. So it can be called only when the CPU (to which we want to bind the task) kthread_bind() does NOT wakeup anything. It merily sets the cpus allowed ptr without further ado. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/