Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932166Ab2BOJ0Q (ORCPT ); Wed, 15 Feb 2012 04:26:16 -0500 Received: from merlin.infradead.org ([205.233.59.134]:47138 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752279Ab2BOJ0N convert rfc822-to-8bit (ORCPT ); Wed, 15 Feb 2012 04:26:13 -0500 Message-ID: <1329297944.2293.36.camel@twins> Subject: Re: bisected: 'perf top' causing soft lockups under Xen From: Peter Zijlstra To: Steven Noonan Cc: Ben Guthro , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Jeremy Fitzhardinge Date: Wed, 15 Feb 2012 10:25:44 +0100 In-Reply-To: <20120215085737.GA13722@asmodeus> References: <1328894901.25989.20.camel@laptop> <20120210190412.GB12975@phenom.dumpdata.com> <20120212205016.GA2794@asmodeus> <20120215085737.GA13722@asmodeus> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1079 Lines: 25 On Wed, 2012-02-15 at 00:57 -0800, Steven Noonan wrote: > It seems to me that there are two options for fixing this, but I'm > probably lacking the necessary context (or experience with Xen). Either: > > - The patch provided by Ben needs to have additional work to specially > handle IRQ_WORK_VECTOR, since it seems to be a special case where > there's no event channel attached for it. Perhaps adding an event > channel for this is the fix? Seems high-overhead, but I lack a good > understanding of how interrupts are handled in Xen. So that's a self-IPI, is Xen failing to implement this? > or > > - Perf needs to be "enlightened" about Xen and avoid sending an IPI in > the first place. Uhm, no. If anything Xen should simply not implement arch_irq_work_raise(). The callbacks are then ran from the timer interrupt. -- 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/