On Thu, Jun 19, 2014 at 10:37:17PM +0200, Thomas Gleixner wrote:
> 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?
That would allow me to keep my code unchanged, so I am in favor. ;-)
Thanx, Paul
> 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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