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Old 06-30-2012, 09:57 PM
Maxim Wexler
 
Default unstoppable, undeciperable kernel call trace in log

Hi group,

Please take a look at this clip from /var/log/messages:

https://paste.lugons.org/show/2679/

Can somebody tell me what it means? It never changes, char by char. It
goes on forever, over and over again. At one time I wanted kernel
debugging, but I've returned to menuconfig and turned it off(I thought
).

How do I stop this pointless verbosity?

Max
 
Old 07-01-2012, 01:25 AM
Paul Hartman
 
Default unstoppable, undeciperable kernel call trace in log

On Sat, Jun 30, 2012 at 4:57 PM, Maxim Wexler <maxim.wexler@gmail.com> wrote:
> Hi group,
>
> Please take a look at this clip from /var/log/messages:
>
> https://paste.lugons.org/show/2679/
>
> Can somebody tell me what it means? It never changes, char by char. It
> goes on forever, over and over again. At one time I wanted kernel
> debugging, but I've returned to menuconfig and turned it off(I thought
> ).
>
> How do I stop this pointless verbosity?

Hi,

I don't have an answer, but if you google the phrase "rcu_bh detected
stall on CPU" you can find many reports similar to yours and maybe
some information.

Do you have RCU_CPU_STALL_INFO=y in your kernel config?
 
Old 07-01-2012, 03:11 AM
Maxim Wexler
 
Default unstoppable, undeciperable kernel call trace in log

> Hi,
>
> I don't have an answer, but if you google the phrase "rcu_bh detected
> stall on CPU" you can find many reports similar to yours and maybe
> some information.

This might be usefu
lhttp://www.kernel.org/doc/Documentation/RCU/stallwarn.txt

"RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE"

from <help> in menuconfig.

│ This option provides tracing in RCU which presents stats │
│ in debugfs for debugging RCU implementation.

Ok, so I've set the RCU_TRACE=y. Next question: How do I use debugfs,
never used it before?

>
> Do you have RCU_CPU_STALL_INFO=y in your kernel config?

no.

syzygy@lumby ~ $ grep RCU /usr/src/linux/.config
# RCU Subsystem
CONFIG_TREE_RCU=y
# CONFIG_PREEMPT_RCU is not set
# CONFIG_RCU_TRACE is not set
CONFIG_RCU_FANOUT=32
# CONFIG_RCU_FANOUT_EXACT is not set
# CONFIG_RCU_FAST_NO_HZ is not set
# CONFIG_TREE_RCU_TRACE is not set
# CONFIG_SPARSE_RCU_POINTER is not set
CONFIG_RCU_CPU_STALL_TIMEOUT=60
 
Old 07-01-2012, 03:46 AM
Maxim Wexler
 
Default unstoppable, undeciperable kernel call trace in log

This is weird

syzygy@lumby ~ $ grep DEBUG_FS /usr/src/linux/.config
# CONFIG_DEBUG_FS is not set

But the entry in menuconfig ->kernel hacking looks like this:' -*-
Debug Filesystem', and can't be changed. Not '[*]' which is
changeable with the spacebar, but '-*-' which is not.

According to <help> it depends on TREE_RCU_TRACE=y OR <a whole bunch
of other stuff>.

But I have TREE_RCU_TRACE=y. So I should be good right? But then why
doesn't it select DEBUG_FS?

googling lead me to http://en.wikipedia.org/wiki/Debugfs, which says
do: 'mount -t debugfs none /sys/kernel/debug'. Ok, but there's no
debug file or dir under /sys/kernel. Do I make one? And will it make a
difference since according to grep DEBUG_FS is not set in the kernel
config?

I'll go and make the new kernel and see what happens.


On 6/30/12, Maxim Wexler <maxim.wexler@gmail.com> wrote:
>> Hi,
>>
>> I don't have an answer, but if you google the phrase "rcu_bh detected
>> stall on CPU" you can find many reports similar to yours and maybe
>> some information.
>
> This might be usefu
> lhttp://www.kernel.org/doc/Documentation/RCU/stallwarn.txt
>
> "RCU bugs can often be debugged with the help of CONFIG_RCU_TRACE"
>
> from <help> in menuconfig.
>
> │ This option provides tracing in RCU which presents stats
> │
> │ in debugfs for debugging RCU implementation.
>
> Ok, so I've set the RCU_TRACE=y. Next question: How do I use debugfs,
> never used it before?
>
>>
>> Do you have RCU_CPU_STALL_INFO=y in your kernel config?
>
> no.
>
> syzygy@lumby ~ $ grep RCU /usr/src/linux/.config
> # RCU Subsystem
> CONFIG_TREE_RCU=y
> # CONFIG_PREEMPT_RCU is not set
> # CONFIG_RCU_TRACE is not set
> CONFIG_RCU_FANOUT=32
> # CONFIG_RCU_FANOUT_EXACT is not set
> # CONFIG_RCU_FAST_NO_HZ is not set
> # CONFIG_TREE_RCU_TRACE is not set
> # CONFIG_SPARSE_RCU_POINTER is not set
> CONFIG_RCU_CPU_STALL_TIMEOUT=60
>
 

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