From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754093Ab0C0A62 (ORCPT ); Fri, 26 Mar 2010 20:58:28 -0400 Received: from rcsinet12.oracle.com ([148.87.113.124]:49255 "EHLO rcsinet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753912Ab0C0A60 (ORCPT ); Fri, 26 Mar 2010 20:58:26 -0400 Date: Fri, 26 Mar 2010 17:57:11 -0700 From: Joel Becker To: Yury Polyanskiy Cc: linux-kernel@vger.kernel.org, Andrew Morton , john stultz , Jan Glauber Subject: Re: [PATCH] hangcheck-timer is broken on x86 Message-ID: <20100327005710.GA31009@mail.oracle.com> Mail-Followup-To: Yury Polyanskiy , linux-kernel@vger.kernel.org, Andrew Morton , john stultz , Jan Glauber References: <20100323233611.6dcbe4f4@penta.localdomain> <20100326214648.GF9984@mail.oracle.com> <20100326180025.052d930f@penta.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100326180025.052d930f@penta.localdomain> X-Burt-Line: Trees are cool. X-Red-Smith: Ninety feet between bases is perhaps as close as man has ever come to perfection. User-Agent: Mutt/1.5.20 (2009-06-14) X-Source-IP: acsmt355.oracle.com [141.146.40.155] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090206.4BAD581E.0191:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 26, 2010 at 06:00:25PM -0400, Yury Polyanskiy wrote: > On Fri, 26 Mar 2010 14:46:49 -0700 > Joel Becker wrote: > > > On Tue, Mar 23, 2010 at 11:36:11PM -0400, Yury Polyanskiy wrote: > > > 1) Does getrawmonotonic() satisfy hangcheck-timer? What I mean is, will > > it always return the wallclock nanoseconds even in the face of CPU speed > > changes, suspend, udelay, or any other suspension of kernel operation? > > Yes, I know this is a tougher standard than rdtsc(), but this is what > > hangcheck-timer wants. rdtsc() at least satisfied udelay and PCI hangs. > > Yes, as far as I can tell. Note that rdtsc is hosed on suspend-resume. Yeah, I know. rdtsc hangcheck-timer really required no suspend or cpufreq. Since it is only really used by servers, this wasn't a terrible restriction. Then virtualization came along... > > 2) If it does satisfy, why not use it for all hangcheck usage instead of > > any ifdefs? > > On my part, I didn't want to touch the S390 code since I can't test it. Makes sense. Andrew, would you mind pushing this through your tree? Acked-by: Joel Becker Joel -- Dort wo man Bücher verbrennt, verbrennt man am Ende auch Mensch. (Wherever they burn books, they will also end up burning people.) - Heinrich Heine Joel Becker Principal Software Developer Oracle E-mail: joel.becker@oracle.com Phone: (650) 506-8127