Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751349AbWCRMgz (ORCPT ); Sat, 18 Mar 2006 07:36:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751447AbWCRMgz (ORCPT ); Sat, 18 Mar 2006 07:36:55 -0500 Received: from mail.tmr.com ([64.65.253.246]:7051 "EHLO gaimboi.tmr.com") by vger.kernel.org with ESMTP id S1751349AbWCRMgz (ORCPT ); Sat, 18 Mar 2006 07:36:55 -0500 Message-ID: <441BFF38.9000300@tmr.com> Date: Sat, 18 Mar 2006 07:38:16 -0500 From: Bill Davidsen Organization: TMR Associates Inc, Schenectady NY User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.11) Gecko/20050729 X-Accept-Language: en-us, en MIME-Version: 1.0 To: =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2201 Lines: 79 M?ns Rullg?rd wrote: >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. > > > Please google "emoticons" and find out what those funny characters at the end of the of the paragraph you quoted really mean. Sheesh! -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - 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/