Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933571AbXEGMkD (ORCPT ); Mon, 7 May 2007 08:40:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933613AbXEGMkC (ORCPT ); Mon, 7 May 2007 08:40:02 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:48255 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933571AbXEGMkA (ORCPT ); Mon, 7 May 2007 08:40:00 -0400 Date: Mon, 7 May 2007 18:09:56 +0530 From: Gautham R Shenoy To: Srivatsa Vaddagiri Cc: Satoru Takeuchi , Linux Kernel , Rusty Russell , Zwane Mwaikambo , Nathan Lynch , Joel Schopp , Ashok Raj , Heiko Carstens Subject: Re: [BUG] cpu-hotplug: Can't offline the CPU with naughty realtime processes Message-ID: <20070507123956.GA11416@in.ibm.com> Reply-To: ego@in.ibm.com References: <87bqgxrlky.wl%takeuchi_satoru@jp.fujitsu.com> <20070507104724.GA10624@in.ibm.com> <20070507110256.GM7311@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070507110256.GM7311@in.ibm.com> User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1390 Lines: 36 On Mon, May 07, 2007 at 04:32:56PM +0530, Srivatsa Vaddagiri wrote: > On Mon, May 07, 2007 at 04:17:24PM +0530, Gautham R Shenoy wrote: > > Nevertheless, with the freezer based approach that we're experimenting, > > this problem shouldn't arise. We expect the whole system to get frozen > > before we actually do a cpu_down() (which will then call > > __stop_machine_run). So any such rogue RT task will have to first fail > > the freezer ( which it will), > > >From what I understand of the freezer, if the RT task is running in user > space (which seems to be the case in this thread), it should get frozen even > if it is a forever running SCHED_FIFO task at MAX_RT_PRIO -1 priority? Yes, you are right. It will end up getting the fake signal. So yeah, freezer pretty much solves the problem for cpu hotplug. But I now wonder if we will have some problem with module stopping if we have a high prio SCHED_FIFO in the system. > > -- > Regards, > vatsa Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - 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/