Messages in this thread | | | Date | Wed, 2 Apr 2008 13:07:19 +0200 | From | Jens Axboe <> | Subject | Re: kmemcheck caught read from freed memory (cfq_free_io_context) |
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On Wed, Apr 02 2008, Pekka Enberg wrote: > Hi Paul, > > On Wed, Apr 2, 2008 at 1:55 PM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > I will check this when I get back to some bandwidth -- but in the meantime, > > does kmemcheck special-case SLAB_DESTROY_BY_RCU? It is legal to access > > newly-freed items in that case, as long as you did rcu_read_lock() > > before gaining a reference to them and don't hold the reference past > > the matching rcu_read_unlock(). > > No, kmemcheck is work in progress and does not know about > SLAB_DESTROY_BY_RCU yet. The reason I asked Vegard to post the warning > was because Peter, Vegard, and myself identified this particular > warning as a real problem. But yeah, kmemcheck can cause false > positives for RCU for now.
Makes sense, and to me Pauls analysis of the code looks totally correct - there's no bug there, at least related to hlist traversal and kmem_cache_free(), since we are under rcu_read_lock() and thus hold off the grace for freeing.
-- Jens Axboe
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