Messages in this thread | | | Date | Fri, 22 Apr 2011 13:35:55 +0200 | From | Jens Axboe <> | Subject | Re: 2.6.39-rc4 BUG: unable to handle kernel NULL pointer dereference at 0000000c IP: cfq_insert_request+0x1d/0x3f5 |
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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 <axboe@kernel.dk> 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
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