Messages in this thread | | | Date | Wed, 20 Apr 2011 15:31:53 +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 2011-04-20 15:29, Michal Hocko wrote: > On Wed 20-04-11 15:13:15, Jens Axboe wrote: >> On 2011-04-20 14:58, Michal Hocko wrote: >>> Hi, >>> I am not able to boot with the current git tree >>> (2.6.39-rc4-00089-g2f666bc). 2.6.39-rc3 boots just fine. >>> >>> The backtrace [1] looks really messy. >>> >>> I have seen a similar backtrace at https://lkml.org/lkml/2011/3/25/169 >>> and tried the patch from https://lkml.org/lkml/2011/3/25/173 but it >>> didn't help. The backtrace looks similar (much smaller) but the machine >>> ends up dead as well with unbalanced preempt counter[2]. >>> >>> The config is attached. >>> >>> Is this a known problem? >>> >>> --- >>> * [1] backtrace with the current git tree (2f666bc) >>> >>> [ 31.207283] BUG: unable to handle kernel NULL pointer dereference at 0000000c >>> NULL pointer dereference[ 31.207540] IP: at 0000000c >>> [ 31.207540] IP: [<c028dece>] cfq_insert_request+0x1d/0x3f5 >>> [ 31.207720] *pde = 00000000 [<c028dece>] cfq_insert_request+0x1d/0x3f5 >>> NULL pointer dereference[ 31.207720] *pde = 00000000 >>> at 0000000c >>> [ 31.207888] Oops: 0000 [#1] >>> PREEMPT [ 31.207540] IP:[ 31.207888] Oops: 0000 [#1] SMP PREEMPT DEBUG_PAGEALLOC [<c028dece>] cfq_insert_request+0x1d/0x3f5 >>> SMP DEBUG_PAGEALLOC[ 31.207720] *pde = 00000000 >>> [ 31.207888] Oops: 0000 [#1] PREEMPT [ 31.208186] last sysfs file: /sys/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/queue/scheduler >> >> Ahh hang on, this may be a good clue. Does your boot scripts change the >> IO scheduler? > > Good one... > Yes, I have: > echo deadline > /sys/block/sda/queue/scheduler > in /etc/rc.local > > I am able to boot after I remove it. This is the first time I have seen > "last sysfs file" being useful.
Haha, good point, it's the first time for me as well IO think.
> Still want me to test the patch from the other email?
No, that wont help you. I do wonder why this is a rc3 vs rc4 change. I'll dig around and send you something to try.
-- Jens Axboe
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