From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754076Ab0C0WEf (ORCPT ); Sat, 27 Mar 2010 18:04:35 -0400 Received: from rcsinet12.oracle.com ([148.87.113.124]:24263 "EHLO rcsinet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754025Ab0C0WEe (ORCPT ); Sat, 27 Mar 2010 18:04:34 -0400 Date: Sat, 27 Mar 2010 15:03:55 -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: <20100327220355.GA1810@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> <20100327005710.GA31009@mail.oracle.com> <20100326220259.702859e9@penta.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100326220259.702859e9@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: acsmt354.oracle.com [141.146.40.154] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090206.4BAE80E3.011E: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 10:02:59PM -0400, Yury Polyanskiy wrote: > Joel, just realized there is a slight mistake in what I said before. > getrawmonotonic() is a refined jiffies (and actually resolves to > get_cycles() on my system in the end). Thus it doesn't count while in > suspend. However, jiffies-based timers (aka timer-wheel) are also > stopped while in suspend. So getrawmonotonic() is the right call to > check the precision of the jiffies-based timer (i.e. you dont need to > make a correction by calling monotonic_to_bootbased()). It's OK to tell hangcheck-timer users that suspend is not allowed. After all, you're running something that you don't want to see hang. Is there a clock in the system that is a true wallclock? I'm guessing, since getrawmonotonic() is get_cycles() based, that it doesn't provide accurate time in the face of cpufreq changes. Is that true? Joel -- Life's Little Instruction Book #497 "Go down swinging." Joel Becker Principal Software Developer Oracle E-mail: joel.becker@oracle.com Phone: (650) 506-8127