Messages in this thread | | | Date | Fri, 22 Apr 2011 09:00:33 +0200 | From | Michal Hocko <> | 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 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! -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic
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