Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261989AbVATAXb (ORCPT ); Wed, 19 Jan 2005 19:23:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262001AbVATAUp (ORCPT ); Wed, 19 Jan 2005 19:20:45 -0500 Received: from moutng.kundenserver.de ([212.227.126.189]:7892 "EHLO moutng.kundenserver.de") by vger.kernel.org with ESMTP id S262000AbVATAQ0 (ORCPT ); Wed, 19 Jan 2005 19:16:26 -0500 Subject: Re: [PATCH]sched: Isochronous class v2 for unprivileged soft rt scheduling From: utz lehmann To: Con Kolivas Cc: LKML , Ingo Molnar , rlrevell@joe-job.com, paul@linuxaudiosystems.com, joq@io.com, CK Kernel , Andrew Morton , alexn@dsv.su.se In-Reply-To: <41EEE1B1.9080909@kolivas.org> References: <41EEE1B1.9080909@kolivas.org> Content-Type: text/plain Date: Thu, 20 Jan 2005 01:16:17 +0100 Message-Id: <1106180177.4036.27.camel@segv.aura.of.mankind> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-3) Content-Transfer-Encoding: 7bit X-Provags-ID: kundenserver.de abuse@kundenserver.de auth:5a3828f1c4d839cf12e8a3b808f7ed34 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2174 Lines: 83 Hi Con On Thu, 2005-01-20 at 09:39 +1100, Con Kolivas wrote: > This is version 2 of the SCHED_ISO patch with the yield bug fixed and > code cleanups. Thanks for the update. @@ -2406,6 +2489,10 @@ void scheduler_tick(void) task_t *p = current; rq->timestamp_last_tick = sched_clock(); + if (iso_task(p) && !rq->iso_refractory) + inc_iso_ticks(rq, p); + else + dec_iso_ticks(rq, p); scheduler_tick() is not only called by the timer interrupt but also form the fork code. Is this intended? I think the accounting for iso_refractory is wrong. Isn't calling it from timer.c::update_process_times() better? And shouldn't real RT task also counted? If RT tasks use 40% cpu you can lockup the system as unprivileged user with SCHED_ISO because it doesn't reach the 70% cpu limit. Futher on i see a fundamental problem with this accounting for iso_refractory. What if i manage as unprivileged user to run a SCHED_ISO task which consumes all cpu and only sleeps very short during the timer interrupt? I think this will nearly lockup or very slow down the system. The iso_cpu limit can't guaranteed. My simple yield DoS don't work anymore. But i found another way. Running this as SCHED_ISO: #include #include #include #include #include struct timeval tv; int a, b, i0, i1; int cpuusage () { struct rusage ru; getrusage(RUSAGE_SELF, &ru); return ru.ru_utime.tv_usec + ru.ru_stime.tv_usec; } int main () { while(1) { a = tv.tv_sec; b = tv.tv_usec; gettimeofday(&tv, 0); i0 = i1; i1 = cpuusage(); if (i0 != i1) { // printf("%d.%06d\t%d.%06d\t%d\t%d\n", // a, b, (int)tv.tv_sec, (int)tv.tv_usec, i0, i1); } } } It stalled the system for a few seconds and the drop it to SCHED_OTHER. Then start a additional SCHED_OTHER cpu hog (while true; do : ; done). The system locks up after a few seconds. sysrq-n causes a reboot. utz - 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/