Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759486Ab2BJRYv (ORCPT ); Fri, 10 Feb 2012 12:24:51 -0500 Received: from casper.infradead.org ([85.118.1.10]:33411 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758253Ab2BJRYt (ORCPT ); Fri, 10 Feb 2012 12:24:49 -0500 Subject: Re: bisected: 'perf top' causing soft lockups under Xen From: Peter Zijlstra To: Konrad Rzeszutek Wilk Cc: Steven Noonan , linux-kernel@vger.kernel.org, Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Jeremy Fitzhardinge In-Reply-To: <20120210161253.GA11690@phenom.dumpdata.com> References: <20120210161253.GA11690@phenom.dumpdata.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 10 Feb 2012 18:24:29 +0100 Message-ID: <1328894669.25989.18.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 986 Lines: 23 On Fri, 2012-02-10 at 11:12 -0500, Konrad Rzeszutek Wilk wrote: > Hm, during bootup what does perf say about the CPU availability? Is > it that it can only do perf via NMI's? We used to pass down if the event came from NMI context or not in order to avoid doing certain things that were not NMI-safe, like wakeups. That patch changed the code so that it always assumed the worst case (NMI) and thus avoids doing such things. All non-NMI-safe operations are pushed out to IRQ context through kernel/irq_work.c. If there's no particular platform support for that, it falls back to doing that work from the timer tick. Now that all _should_ just work but clearly there's a problem there. I haven't tried making sense of the traces yet.. -- 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/