From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933298AbYFFVeA (ORCPT ); Fri, 6 Jun 2008 17:34:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759356AbYFFVdv (ORCPT ); Fri, 6 Jun 2008 17:33:51 -0400 Received: from E23SMTP06.au.ibm.com ([202.81.18.175]:55587 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756850AbYFFVdv (ORCPT ); Fri, 6 Jun 2008 17:33:51 -0400 Date: Fri, 6 Jun 2008 14:33:45 -0700 From: "Paul E. McKenney" To: Corey Minyard Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, dvhltc@us.ibm.com, niv@us.ibm.com Subject: Re: Recoverable MCA interrupts from NMI handlers? IPMI and RCU? Message-ID: <20080606213345.GD25053@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20080606152134.GA13641@linux.vnet.ibm.com> <4849A3AC.5090107@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4849A3AC.5090107@acm.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 06, 2008 at 03:53:00PM -0500, Corey Minyard wrote: > Paul E. McKenney wrote: > >Hello! > > > >A couple of questions about the x86 architecture... > > > >1. Can recoverable machine-check exceptions occur from within > > NMI handlers? If so, there is a bug in preemptable RCU's > > CONFIG_NO_HZ handling that could be fixed by a patch something > > like the one shown below (untested, probably does not even > > compile). > > > >2. Does the IPMI subsystem make use of RCU read-side primitives > > from within SMI handlers? If so, we need the SMI handlers to > > invoke rcu_irq_enter() upon entry and rcu_irq_exit() upon exit > > when they are invoked from dynticks idle state. Or something > > similar, depending on restrictions on code within SMI handlers. > > > If you mean the IPMI driver, it does not tie into any SMI. It > theoretically could since there's a bit for that in the watchdog timer, > but there's been no demand and I haven't looked at it. I guess it would > be better than an NMI. > > If it did tie in, it would most likely just panic to get useful > information out before the watchdog reset the system. Thanks for the info! I will stop worrying about SMIs and RCU, then. Thanx, Paul