Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932705Ab1CWVRA (ORCPT ); Wed, 23 Mar 2011 17:17:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31555 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754434Ab1CWVQ7 (ORCPT ); Wed, 23 Mar 2011 17:16:59 -0400 Date: Wed, 23 Mar 2011 17:16:56 -0400 From: Don Zickus To: Cyrill Gorcunov Cc: Ingo Molnar , Lin Ming , Jason Wessel , lkml Subject: Re: [PATCH -tip] kgdb, x86: Pull up NMI notifier handler priority Message-ID: <20110323211656.GA29184@redhat.com> References: <4D8A58E1.5090509@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D8A58E1.5090509@openvz.org> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1419 Lines: 35 On Wed, Mar 23, 2011 at 11:32:33PM +0300, Cyrill Gorcunov wrote: > kgdb needs IPI to be sent and handled before perf > or anything else NMI, otherwise kgdb hangs with bootup > self-tests (found on P4 HT SMP machine). Raise its priority > so that we're called first in a notifier chain. This is only because P4 perf swallows all the nmis. If that is the case you are arguing to make the perf nmi at the bottom of the priority list, which is probably not where it should be due to its volume. I am stuck debugging P4 problems again for RHEL-6 and I noticed a small change that is needed (didn't help my problem though) but it looked like an oversight that might help your case. Cheers, Don diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c index 3769ac8..d945314 100644 --- a/arch/x86/kernel/cpu/perf_event_p4.c +++ b/arch/x86/kernel/cpu/perf_event_p4.c @@ -777,6 +787,7 @@ static inline int p4_pmu_clear_cccr_ovf(struct hw_perf_event *hwc) * the counter has reached zero value and continued counting before * real NMI signal was received: */ + rdmsrl(hwc->event_base, v); if (!(v & ARCH_P4_UNFLAGGED_BIT)) return 1; -- 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/