From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757873Ab1ANPz1 (ORCPT ); Fri, 14 Jan 2011 10:55:27 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:45508 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757354Ab1ANPzW (ORCPT ); Fri, 14 Jan 2011 10:55:22 -0500 Subject: Re: [PATCH] acpi/pm: If failed at validating ACPI PM timer, inhibit future reads. From: john stultz To: Konrad Rzeszutek Wilk Cc: Thomas Gleixner , "Kirill A. Shutemov" , Jeremy Fitzhardinge , Stefano Stabellini , Ian Campbell , mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, andi@firstfloor.org, williams@redhat.com, schwidefsky@de.ibm.com, mingo@elte.hu, linux-tip-commits@vger.kernel.org In-Reply-To: <1295019849.2655.8.camel@work-vm> References: <20110111081352.GA22867@shutemov.name> <20110111083054.GB22867@shutemov.name> <20110111095640.GC22867@shutemov.name> <20110113174909.GA28738@dumpdata.com> <1294941698.5617.12.camel@work-vm> <20110113214022.GA12097@dumpdata.com> <20110114140941.GA3062@dumpdata.com> <1295019849.2655.8.camel@work-vm> Content-Type: text/plain; charset="UTF-8" Date: Fri, 14 Jan 2011 07:54:47 -0800 Message-ID: <1295020487.2655.17.camel@work-vm> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-01-14 at 07:44 -0800, john stultz wrote: > I'm actually looking at a different fix, as I'm worried by Thomas' > comment about hitting the same issue on real hardware if we catch the > same pmtrm value both times. Konrad: Mind trying the following? The conditional (!hpet && !ref_start && !ref_stop) doesn't really make sense. If the refs are null, but hpet is on, we still want to break out. So checking if both the ref values are the same should handle if we don't have hardware (both null) or if they are the same value (either by invalid hardware, or by chance), which can cause a divzero issue. NOT FOR INCLUSION, I haven't had my coffee yet. Signed-off-by: John Stultz diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 823f79a..fa2cb5e 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -935,7 +935,7 @@ static void tsc_refine_calibration_work(struct work_struct *work) tsc_stop = tsc_read_refs(&ref_stop, hpet); /* hpet or pmtimer available ? */ - if (!hpet && !ref_start && !ref_stop) + if (ref_start == ref_stop) goto out; /* Check, whether the sampling was disturbed by an SMI */