Subject: Re: [PATCH 4/4] powerpc: Enable lockup and hung task detectors in pseriesand ppc64 defeconfigs

From: Anton Blanchard <[email-masked]>
Date: Wed, 20 Jul 2011 09:46:40 +1000

Hi David,

> > As a result of changes to Kconfig files, we no longer enable
> > the lockup and hung task detectors. Both are very light weight
> > and provide useful information in the event of a hang, so
> > reenable them.
> ...
> > +CONFIG_LOCKUP_DETECTOR=y
> > +CONFIG_DETECT_HUNG_TASK=y
> 
> Is one of thise responsible for generating a kernel stack traceback
> when a process has been sleeping uninterruptably for a 'long' time?
> 
> We have a kernel subsystem that has several 'worker' threads,
> these always sleep uninterruptable (they are shut down by explicit
> request) and, at times, can be idle for long periods.
> 
> Perhaps it should be possible to disable the check either on
> a per-process of per sleep basis?

I don't see any runtime options other than disabling it completely via:

/proc/sys/kernel/hung_task_timeout_secs

Anton