From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755729Ab1HCTpG (ORCPT ); Wed, 3 Aug 2011 15:45:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59377 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755596Ab1HCToz (ORCPT ); Wed, 3 Aug 2011 15:44:55 -0400 Date: Wed, 3 Aug 2011 15:44:38 -0400 From: Don Zickus To: ZAK Magnus Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Mandeep Singh Baines Subject: Re: [PATCH v3 2/2] Make hard lockup detection use timestamps Message-ID: <20110803194438.GA20762@redhat.com> References: <20110725124451.GA2866@redhat.com> <20110729205538.GD14343@redhat.com> <20110801125234.GE14343@redhat.com> <20110801192407.GE2581@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed, Aug 03, 2011 at 11:27:16AM -0700, ZAK Magnus wrote: > An update: > > I realized that the timing function I was using was no good. On x86 it > will try to use the TSC but if it can't (which, as I understand, isn't > a very rare case), it will fall back on a jiffies-based solution. If > interrupts are disabled, time would appear to "stand still" and > lockups wouldn't be detected. So, looks like I have to nix this > particular patch and not change the hard lockup detection that much. Hmm, I was initially worried about that, but after seeing the function you were using assuming Peter vetted it properly to use cleanly from an NMI context. I guess I didn't fully understand the limitations of it. > > Meanwhile, I'm working on printing stack traces to a buffer/out to > file. I got some help and it looks like it's not that hard to do. I'll > send it when it's ready. Interesting. I look forward to seeing it. Cheers, Don