From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752983Ab2HYVPf (ORCPT ); Sat, 25 Aug 2012 17:15:35 -0400 Received: from nctlincom01.orcon.net.nz ([60.234.4.74]:48951 "EHLO nctlincom01.orcon.net.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751079Ab2HYVPc (ORCPT ); Sat, 25 Aug 2012 17:15:32 -0400 Message-ID: <5039406F.9040604@orcon.net.nz> Date: Sun, 26 Aug 2012 09:15:27 +1200 From: Michael Cree User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20120724 Icedove/3.0.11 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Frederic Weisbecker , Ben Hutchings , LKML , Chris Zankel , "3.2.x.." , Chen Liqin , Lennox Wu , "James E.J. Bottomley" , Helge Deller , Parisc , David Howells , Koichi Yasutake , Geert Uytterhoeven , m68k , Hirokazu Takata , Yoshinori Sato , Mikael Starvik , Jesper Nilsson , Cris , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha Subject: Re: [PATCH 00/11] rcu: Add missing RCU idle APIs on idle loop v2 References: <1345733915-20040-1-git-send-email-fweisbec@gmail.com> <20120824212647.GU2472@linux.vnet.ibm.com> <1345857554.4840.43.camel@deadeye.wl.decadent.org.uk> <20120825035047.GB3436@linux.vnet.ibm.com> <20120825131647.GA1994@somewhere> <20120825161806.GD3436@linux.vnet.ibm.com> In-Reply-To: <20120825161806.GD3436@linux.vnet.ibm.com> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-DSPAM-Check: by mx4.orcon.net.nz on Sun, 26 Aug 2012 09:15:28 +1200 X-DSPAM-Result: Innocent X-DSPAM-Processed: Sun Aug 26 09:15:29 2012 X-DSPAM-Confidence: 0.7006 X-DSPAM-Probability: 0.0000 X-Bayes-Prob: 0.0001 (Score 0, tokens from: @@RPTN, default) X-Spam-Score: 0.00 () [Hold at 5.50] X-CanIt-Geo: ip=60.234.221.162; country=NZ; region=G2; city=Porirua; latitude=-41.1333; longitude=174.8500; http://maps.google.com/maps?q=-41.1333,174.8500&z=6 X-CanItPRO-Stream: base:default X-Canit-Stats-ID: 06HP9p2gc - 49d4521b9b8f - 20120826 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/08/12 04:18, Paul E. McKenney wrote: > On Sat, Aug 25, 2012 at 03:16:49PM +0200, Frederic Weisbecker wrote: >> On Fri, Aug 24, 2012 at 08:50:47PM -0700, Paul E. McKenney wrote: >>> On Sat, Aug 25, 2012 at 02:19:14AM +0100, Ben Hutchings wrote: >>>> On Fri, 2012-08-24 at 14:26 -0700, Paul E. McKenney wrote: >>>>> On Thu, Aug 23, 2012 at 04:58:24PM +0200, Frederic Weisbecker wrote: >>>>>> Hi, >>>>>> >>>>>> Changes since v1: >>>>>> >>>>>> - Fixed preempt handling in alpha idle loop >>>>>> - added ack from Geert >>>>>> - fixed stable email address, sorry :-/ >>>>>> >>>>>> This time I built tested everywhere but: h8300 (compiler internal error), >>>>>> and mn10300, parisc, score (cross compilers not available in >>>>>> ftp://ftp.kernel.org/pub/tools/crosstool/files/bin/x86_64/4.6.3/) >>>>>> >>>>>> For testing, you can pull from: >>>>>> >>>>>> git://github.com/fweisbec/linux-dynticks.git >>>>>> rcu/idle-fix-v2 >>>>>> >>>>>> Thanks. >>>>> >>>>> I have queued these on -rcu branch rcu/idle: >>>>> >>>>> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git >>>>> >>>>> This problem has been in place since 3.3, so it is hard to argue that >>>>> it is a regression for this merge window. I have therefore queued it >>>>> for 3.7. >>>> >>>> I don't follow that; I would expect any serious bug fix (serious enough >>>> for a stable update) to be acceptable for 3.6 at this point. >>> >>> OK, if any of the arch maintainers wishes to submit the patch to 3.6, >>> they are free to do so -- just let me know and I will drop the patch from >>> my tree. >>> >>> That said, all this does is cause spurious warnings to be printed, so >>> not sure it really qualifies as serious. But I am happy to leave that >>> decision with the individual arch maintainers -- it is their arch, >>> after all, so their decision. >> >> Couldn't that cause hung tasks due to long lasting synchronize_rcu() ? > > In theory, definitely. In practice, they haven't been running into it, > or they would be reporting hangs. I am hereby reporting that RCU CPU stall warnings and hung tasks are being experienced on SMP kernels built for generic Alpha. This problem dates back quite a few kernel releases. The discussed patches appear to fix the problem. A backport to the 3.2 kernel, of at least the Alpha patches, would be very much appreciated! :-) Cheers Michael.