Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755188Ab1DVLgI (ORCPT ); Fri, 22 Apr 2011 07:36:08 -0400 Received: from mx2.fusionio.com ([64.244.102.31]:40311 "EHLO mx2.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755066Ab1DVLgD (ORCPT ); Fri, 22 Apr 2011 07:36:03 -0400 X-ASG-Debug-ID: 1303472159-01de284cf817efc0001-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4DB1681B.9060208@fusionio.com> Date: Fri, 22 Apr 2011 13:35:55 +0200 From: Jens Axboe MIME-Version: 1.0 To: Michal Hocko CC: Linus Torvalds , Jens Axboe , LKML Subject: Re: 2.6.39-rc4 BUG: unable to handle kernel NULL pointer dereference at 0000000c IP: cfq_insert_request+0x1d/0x3f5 References: <20110420125824.GA3507@tiehlicka.suse.cz> <4DAEDBEB.7060904@fusionio.com> <20110420132903.GA13554@tiehlicka.suse.cz> <4DAF18DF.9080205@fusionio.com> <20110421071642.GA3556@tiehlicka.suse.cz> <5F35AAD2-8277-44BD-86B6-B1D7B816071E@kernel.dk> <20110421185112.GA4796@tiehlicka.suse.cz> <4DB07ECA.5050309@fusionio.com> <20110422070032.GA3575@tiehlicka.suse.cz> X-ASG-Orig-Subj: Re: 2.6.39-rc4 BUG: unable to handle kernel NULL pointer dereference at 0000000c IP: cfq_insert_request+0x1d/0x3f5 In-Reply-To: <20110422070032.GA3575@tiehlicka.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1303472159 X-Barracuda-URL: http://10.101.1.181:8000/cgi-mod/mark.cgi X-Barracuda-Spam-Score: 0.20 X-Barracuda-Spam-Status: No, SCORE=0.20 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests=PR0N_SUBJECT X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.61594 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- 0.20 PR0N_SUBJECT Subject has letters around special characters (pr0n) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1916 Lines: 50 On 2011-04-22 09:00, Michal Hocko wrote: > On Thu 21-04-11 21:00:26, Jens Axboe wrote: >> On 2011-04-21 20:51, Michal Hocko wrote: >>> On Thu 21-04-11 07:38:57, Linus Torvalds wrote: >>>> On Thu, Apr 21, 2011 at 12:25 AM, Jens Axboe wrote: >>>>>> >>>>>> I am going to bisect, let's see if I can find anything. >>>>> >>>>> Thanks, that would be great! >>>> >>>> I'd expect it to be very timing-dependent, and thus could easily be >>>> triggered (or hidden) by unrelated changes. >>>> >>>> Just happening to have a request added to the elevator at _just_ the >>>> same moment that another CPU is changing it and getting rid of the >>>> data structures for the old one. >>> >>> And it really looks like a timing issue. I have bisected down to >>> e710d7d5a9cab1041b7a3cf9e655b75d92786857. I had to skip[1] some commits >>> due to compile errors [2]. >>> At first it looked quite promising because I was able to boot after I >>> reverted that patch but then I have tried to revert it on top of rc4 >>> (2f666bcf757cb72549f360ef6da02f03620a48b6) and saw the same problem >>> again. >>> >>> So I do not think that bisecting will help here. >> >> It will be timing dependent. If there's no allocated IO requests when >> the switch happens, it'll work. >> >> But the commit that caused this regression is 5e84ea3a. If you revert >> that, it should work fine. Or just apply the patch I sent (or update to >> Linus' tree, it's in now) and it'll work as well. > > Great. I can boot just fine with the current Linus tree > (2.6.39-rc4-00149-g91e8549). > > Thanks a lot! Great, with that confirmed from you, we have no pending bugs in this area. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/