Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request duringshutdown

From: Knut Petersen
Date: Mon Oct 28 2013 - 11:45:28 EST


On 28.10.2013 16:16, Ingo Molnar wrote:
* Ingo Molnar <mingo@xxxxxxxxxx> wrote:

I tried that patch, together with all the kobj debug options
enabled. With that kernel configuration I was unable to
reproduce the problem during 500 typical workload / reboot
cycles. Without the debug options I was able to reproduce the
last reported panic after 91 cycles. The debug options seem to
change timing sufficiently to mask the bug ;-(
Could you send me the kernel config please?
I got your .config off-list, thanks Knut!

It has all DEBUG_OBJECT options enabled:

CONFIG_DEBUG_OBJECTS=y
# CONFIG_DEBUG_OBJECTS_SELFTEST is not set
CONFIG_DEBUG_OBJECTS_FREE=y
CONFIG_DEBUG_OBJECTS_TIMERS=y
CONFIG_DEBUG_OBJECTS_WORK=y
CONFIG_DEBUG_OBJECTS_RCU_HEAD=y
CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER=y
CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT=1

but it also has DEBUG_PAGEALLOC enabled:

CONFIG_DEBUG_PAGEALLOC=y

I'd suggest disabling that one - it kind of overlaps debugobjects
and it will definitely be a big slowdown.

ACK
I'd also suggest turning off lockdep for now:

CONFIG_PROVE_LOCKING=y

because we know it does not trigger any useful warning. This too
should speed up things a bit.

Well, for now that´s true. On one machine it emits the old warning about the
videobuf_dvb_find_frontend() / dvb_device_open() circular reference,
but that´s definitely unrelated.


Whether this would make the crash reproducable again I don't know
:-/

We´ll see ;-)
Thanks,

Ingo


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