Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750897AbWCPWvd (ORCPT ); Thu, 16 Mar 2006 17:51:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964892AbWCPWvd (ORCPT ); Thu, 16 Mar 2006 17:51:33 -0500 Received: from [82.153.166.94] ([82.153.166.94]:7398 "EHLO mail.inprovide.com") by vger.kernel.org with ESMTP id S1750897AbWCPWvc convert rfc822-to-8bit (ORCPT ); Thu, 16 Mar 2006 17:51:32 -0500 To: Bill Davidsen Cc: linux-kernel@vger.kernel.org Subject: Re: can I bring Linux down by running "renice -20 cpu_intensive_process"? References: <441180DD.3020206@wpkg.org> <1142135077.25358.47.camel@mindpipe> <4419D575.4080203@tmr.com> From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= Date: Thu, 16 Mar 2006 22:51:16 +0000 In-Reply-To: <4419D575.4080203@tmr.com> (Bill Davidsen's message of "Thu, 16 Mar 2006 16:15:33 -0500") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.15 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1728 Lines: 44 Bill Davidsen writes: > M?ns Rullg?rd wrote: >> Lee Revell writes: >> >>> On Fri, 2006-03-10 at 22:01 +0000, M?ns Rullg?rd wrote: >>>> Jan Engelhardt writes: >>>> >>>>>> Subject: can I bring Linux down by running "renice -20 >>>>>> cpu_intensive_process"? >>>>>> >>>>> Depends on what the cpu_intensive_process does. If it tries to >>>>> allocate lots of memory, maybe. If it's _just_ CPU (as in `perl >>>>> -e '1 while 1'`), you get a chance that you can input some >>>>> commands on a terminal to kill it. SCHED_FIFO'ing or >>>>> SCHED_RR'ing such a process is sudden death of course. >>>> Sysrq+n changes all realtime tasks to normal priority. >>>> >>> A nice -20 SCHED_OTHER task is not realtime, only SCHED_FIFO and >>> SCHED_RR. >> Maybe extending sysrq+n to lower the priority of -20 tasks would be a >> good idea. >> > If it runs before the keyboard thread it doesn't matter... Of course not, but that's not generally the case. > But why should this hang anything, when there should be enough i/o > to get out of the user process. There's a good fix for this, don't > give this guy root any more ;-) Ever heard of bugs? Anyone developing a program can make a mistake. If the program runs with realtime scheduling a bug that makes it enter an infinite loop (or do something else that hogs the CPU) can be difficult to find since it rather efficiently locks you out. -- M?ns Rullg?rd mru@inprovide.com - 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/