From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932860AbYFFUxo (ORCPT ); Fri, 6 Jun 2008 16:53:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932130AbYFFUxT (ORCPT ); Fri, 6 Jun 2008 16:53:19 -0400 Received: from vms173003pub.verizon.net ([206.46.173.3]:50165 "EHLO vms173003pub.verizon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765208AbYFFUxS (ORCPT ); Fri, 6 Jun 2008 16:53:18 -0400 Date: Fri, 06 Jun 2008 15:53:00 -0500 From: Corey Minyard Subject: Re: Recoverable MCA interrupts from NMI handlers? IPMI and RCU? In-reply-to: <20080606152134.GA13641@linux.vnet.ibm.com> To: paulmck@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, dvhltc@us.ibm.com, niv@us.ibm.com Message-id: <4849A3AC.5090107@acm.org> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: <20080606152134.GA13641@linux.vnet.ibm.com> User-Agent: Mozilla-Thunderbird 2.0.0.14 (X11/20080509) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -corey