On Thu, 19 Jun 2014, Paul E. McKenney wrote:
> On Thu, Jun 19, 2014 at 09:29:08PM +0200, Thomas Gleixner wrote:
> > On Thu, 19 Jun 2014, Paul E. McKenney wrote:
> > Well, no. Look at the callchain:
> >
> > __call_rcu
> > debug_object_activate
> > rcuhead_fixup_activate
> > debug_object_init
> > kmem_cache_alloc
> >
> > So call rcu activates the object, but the object has no reference in
> > the debug objects code so the fixup code is called which inits the
> > object and allocates a reference ....
>
> OK, got it. And you are right, call_rcu() has done this for a very
> long time, so not sure what changed. But it seems like the right
> approach is to provide a debug-object-free call_rcu_alloc() for use
> by the memory allocators.
>
> Seem reasonable? If so, please see the following patch.
Not really, you're torpedoing the whole purpose of debugobjects :)
So, why can't we just init the rcu head when the stuff is created?
If that's impossible due to other memory allocator constraints, then
instead of inventing a whole new API we can simply flag the relevent
data in the memory allocator as we do with the debug objects mem cache
itself (SLAB_DEBUG_OBJECTS).
Thanks,
tglx
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