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    SubjectRe: slub/debugobjects: lockup when freeing memory
    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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