From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753195AbbBEUtP (ORCPT ); Thu, 5 Feb 2015 15:49:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33478 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752169AbbBEUtO (ORCPT ); Thu, 5 Feb 2015 15:49:14 -0500 Date: Thu, 5 Feb 2015 15:48:49 -0500 From: Don Zickus To: Cyril Bur Cc: linux-kernel@vger.kernel.org, mpe@ellerman.id.au, drjones@redhat.com, akpm@linux-foundation.org, mingo@kernel.org, uobergfe@redhat.com, chaiw.fnst@cn.fujitsu.com, fabf@skynet.be, atomlin@redhat.com, benzh@chromium.org, schwidefsky@de.ibm.com Subject: Re: [PATCH v2 0/2] Quieten softlockup detector on virtualised kernels Message-ID: <20150205204849.GS234357@redhat.com> References: <1420774478-16760-1-git-send-email-cyrilbur@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1420774478-16760-1-git-send-email-cyrilbur@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 09, 2015 at 02:34:36PM +1100, Cyril Bur wrote: > When the hypervisor pauses a virtualised kernel the kernel will observe a jump > in timebase, this can cause spurious messages from the softlockup detector. > > Whilst these messages are harmless, they are accompanied with a stack trace > which causes undue concern and more problematically the stack trace in the > guest has nothing to do with the observed problem and can only be misleading. Originally I was suggesting to talk with the x86/kvm folks about coming up with a common solution. But I didn't hear a response from those cc'd at the time. This solution looks a lot cleaner than what x86 is doing. I am willing to see how this works out on ppc64's kvm and see if they still see any issues after awhile. If not, maybe I can poke the x86 folks to migrate to something similar. Acked-by: Don Zickus > > Futhermore, on POWER8 this is completely avoidable with the introduction of > the Virtual Time Base (VTB) register. > > V2: > Remove the export of running_clock > Added #ifdef CONFIG_PPC_PSERIES and optimised the non lpar + vtb cases. > Replaced the use of sched_clock_with local_clock it was used originally in > the softlockup detector. > > Cyril Bur (2): > Add another clock for use with the soft lockup watchdog. > powerpc: add running_clock for powerpc to prevent spurious softlockup > warnings > > arch/powerpc/kernel/time.c | 32 ++++++++++++++++++++++++++++++++ > include/linux/sched.h | 1 + > kernel/sched/clock.c | 13 +++++++++++++ > kernel/watchdog.c | 2 +- > 4 files changed, 47 insertions(+), 1 deletion(-) > > -- > 1.9.1 >