Re: 2.6.24-rc7 lockdep warning when poweroff

[Peter Zijlstra <peterz@infradead.org>]

On Tue, 2008-01-15 at 09:24 +0800, Dave Young wrote:
> On Tue, Jan 15, 2008 at 08:31:48AM +0800, Dave Young wrote:
> > On Jan 14, 2008 6:51 PM, Johannes Berg <johannes@sipsolutions.net> wrote:
> > >
> > > > The warning that triggered (lockdep.c:700) means that one class (key)
> > > > was used with more than one name.
> > >
> > > Right.
> > >
> > > > Looking at cleanup_workqueue_thread(), the lock_acquire() there works on
> > > > wq->lockdep_map, and that is only initialized at one spot:
> > > > __create_workqueue_key(), thus it stands to reason that that was
> > > > mis-used.
> > >
> > > Oh ok, yes, makes sense. Maybe something is generating a workqueue with
> > > a name that's passed in but the key is statically from that place. I'll
> > > try to find it.
> > 
> > I add some debug printk and found the names :
> > 
> > block_osm/exec_osm
> > 
> > in drivers/message/i2o
> > 
> > maybe this helps.
> 
> Not sure right or not, the following patch fixed the problem:
> 
> diff -upr linux/include/linux/workqueue.h linux.new/include/linux/workqueue.h
> --- linux/include/linux/workqueue.h	2008-01-15 08:49:08.000000000 +0800
> +++ linux.new/include/linux/workqueue.h	2008-01-15 08:49:42.000000000 +0800
> @@ -154,7 +154,7 @@ __create_workqueue_key(const char *name,
>  #ifdef CONFIG_LOCKDEP
>  #define __create_workqueue(name, singlethread, freezeable)	\
>  ({								\
> -	static struct lock_class_key __key;			\
> +	struct lock_class_key __key;			\
>  								\
>  	__create_workqueue_key((name), (singlethread),		\
>  			       (freezeable), &__key);		\

That didn't get you:

  INFO: trying to register non-static key.

Msgs?

But it sure looks like __create_workqueue() is asking for trouble, if
there is a __create_workqueue() instance that takes a non constant name
we're in trouble.