Re: 2.6.17-mm1 - possible recursive locking detected

[Andrew Morton <akpm@osdl.org>]

On Thu, 22 Jun 2006 03:40:36 -0400
"Brown, Len" <len.brown@intel.com> wrote:

> >> Nothing jumps out at me as incorrect above, so 
> >> at this point it looks like a CONFIG_LOCKDEP artifact --
> >> but lets ask the experts:-)
> >
> >Yes, lockdep uses the callsite of spin_lock_init() to detect 
> >the "type" of
> >a lock.
> >
> >But the ACPI obfuscation layers use the same spin_lock_init() site to
> >initialise two not-the-same locks, so lockdep decides those 
> >two locks are of the same "type" and gets confused.
> 
> interesting definition of "type".  I guess it works
> in practice or others would be complaining...

It works out that way, yes.

> >We had earlier decided to remove that ACPI code which kmallocs a single
> >spinlock.  When that's done, lockdep will become unconfused.
> 
> Yes, that change is already on the way.

Is good.

> The key thing here is that our recent changes in
> how the locks are _used_ is okay -- and I think it is.

Well.  We don't know that.  We just know that this report of unokayness
wasn't right.  With Ingo's Linux-only patch we're in a position to verify
that the locking is probably OK.