Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751073AbWELILc (ORCPT ); Fri, 12 May 2006 04:11:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751062AbWELILc (ORCPT ); Fri, 12 May 2006 04:11:32 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:44262 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751073AbWELILb (ORCPT ); Fri, 12 May 2006 04:11:31 -0400 Date: Fri, 12 May 2006 10:10:56 +0200 From: Ingo Molnar To: Steven Rostedt Cc: john stultz , lkml , Mark Hounschell , Thomas Gleixner Subject: Re: [RFC][PATCH -rt] irqd starvation on SMP by a single process? Message-ID: <20060512081056.GA25378@elte.hu> References: <1147401812.1907.14.camel@cog.beaverton.ibm.com> <20060512055025.GA25824@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.8 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.8 required=5.9 tests=ALL_TRUSTED,AWL autolearn=no SpamAssassin version=3.0.3 -2.8 ALL_TRUSTED Did not pass through any untrusted hosts 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1454 Lines: 45 * Steven Rostedt wrote: > On Fri, 12 May 2006, Ingo Molnar wrote: > > > ah. This actually uncovered a real bug. We were calling __do_softirq() > > with interrupts enabled (and being preemptible) - which is certainly > > bad. > > Hmm, I wonder if this is also affecting Mark's problem. > > But since I showed that if hardirqs_disabled and running PREEMPT not > PREEMPT_RT, disable_irq can call schedule. This is done in > drivers/net/3c59x.c. It has a watchdog timeout calling disable_irq, > which calls synchronize_irq which might schedule: > > void synchronize_irq(unsigned int irq) > { > struct irq_desc *desc = irq_desc + irq; > > if (irq >= NR_IRQS) > return; > > if (hardirq_preemption && !(desc->status & IRQ_NODELAY)) > wait_event(desc->wait_for_handler, > !(desc->status & IRQ_INPROGRESS)); > else > while (desc->status & IRQ_INPROGRESS) > cpu_relax(); > } > > -- Steve > > > > > this was hidden before because the smp_processor_id() debugging code > > handles tasks bound to a single CPU as per-cpu-safe. > > > > could you check the (totally untested) patch below and see if that fixes > > things for you? I've also added your affinity change. > > - 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/