Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932277AbWJYTxM (ORCPT ); Wed, 25 Oct 2006 15:53:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932278AbWJYTxL (ORCPT ); Wed, 25 Oct 2006 15:53:11 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:44197 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S932277AbWJYTxK (ORCPT ); Wed, 25 Oct 2006 15:53:10 -0400 Subject: Re: oprofile can cause an NMI to schedule (was: [RT] scheduling and oprofile) From: Lee Revell To: Mike Kravetz Cc: Steven Rostedt , John Levon , phil.el@wanadoo.fr, Ingo Molnar , linux-kernel@vger.kernel.org, oprofile-list@lists.sourceforge.net, george@mvista.com In-Reply-To: <20061025185813.GA4114@monkey.ibm.com> References: <20061023212307.GA21498@monkey.beaverton.ibm.com> <1161656674.13276.17.camel@localhost.localdomain> <20061024124650.GA2668@totally.trollied.org> <20061025185813.GA4114@monkey.ibm.com> Content-Type: text/plain Date: Wed, 25 Oct 2006 15:52:59 -0400 Message-Id: <1161805980.3982.319.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 851 Lines: 19 On Wed, 2006-10-25 at 11:58 -0700, Mike Kravetz wrote: > Newer RT kernels (such as linux-2.6.18-rt5) have reenabled the > add_preempt_count/sub_preempt_count calls in nmi_enter/exit. If I > understand correctly the reason one could not modify the preempt_count > from NMI code is that it could have been in the process of being > modified by non-NMI code. But, in recent RT kernels it appears that > preempt_count is still a single word modified by both NMI and > non-NMI code. What am I missing that now makes this safe? > It's not safe. NMI causes hard lockups on 2.6.18-rt5. Get 2.6.18-rt7. Lee - 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/