Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752254AbbFSQaP (ORCPT ); Fri, 19 Jun 2015 12:30:15 -0400 Received: from www.linutronix.de ([62.245.132.108]:58731 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751637AbbFSQaI (ORCPT ); Fri, 19 Jun 2015 12:30:08 -0400 Date: Fri, 19 Jun 2015 18:30:08 +0200 (CEST) From: Thomas Gleixner To: Jiang Liu cc: Sergey Senozhatsky , Borislav Petkov , linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: Re: [-next] !irqd_can_balance() WARNINGs at irq_move_masked_irq() In-Reply-To: <5584418D.50408@linux.intel.com> Message-ID: References: <20150619071123.GA511@swordfish> <55843EC9.9000401@linux.intel.com> <55843F79.4000606@linux.intel.com> <5584418D.50408@linux.intel.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2168 Lines: 51 On Sat, 20 Jun 2015, Jiang Liu wrote: > On 2015/6/20 0:15, Thomas Gleixner wrote: > > On Sat, 20 Jun 2015, Jiang Liu wrote: > > > >> [...] > >>>> Something in the kernel (not yet clear what) tries to move the hpet > >>>> irq 0 by calling irq_set_affinity(). That's an kernel internal > >>>> interface which does not check whether the NO BALANCE flag is set for > >>>> the irq. So the call runs and triggers the move from next interrupt > >>>> machinery which ends up calling irq_move_masked_irq() and that trips > >>>> over the flag and yells. > >>>> > >>>> That's why I changed the WARN to a pr_warn() because we already know > >>>> the call stack. > >>>> > >>>> So the core behaviour is inconsistent. We let the caller of > >>>> irq_set_affinity() succeed and yell later because we think it's wrong. > >>>> > >>>> I'm pretty sure that we must drop the check for NO BALANCE in > >>>> irq_move_masked_irq() and only check for the per_cpu bit, but at the > >>>> same time I really want to know where that call to irq_set_affinity(irq0) > >>>> is coming from. > >>>> > >>>> Can you please collect the output of /proc/timer_list for the previous > >>>> patch and then replace the previous patch with the one below and > >>>> gather all the data again? > >>> > >>> Hi Thomas, > >>> Maybe it's caused by the hpet driver itself? > >>> irq_set_affinity() may set the IRQD_SETAFFINITY_PENDING flag, > >>> thus triggering the warning. > >> And the usage pattern seems reasonable, the IRQF_NOBALANCING flag > >> means nobody may change the affinity except myself:) > > > > Right, that's why I removed the restriction. I just wonder why we have > > not seen that before ... > I suspected it's caused by the hierarchy irqdomain at first glance > because the multiple irq_datas issue, but seems it's not after checking > the code. It will only be triggered if HPET works in MSI mode instead of > legacy IRQ mode, but still need more investigation here. Right. And what confuses me is that this happens on irq0, which is ioapic edge. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/