Messages in this thread | | | Subject | Re: kmemcheck caught read from freed memory (cfq_free_io_context) | From | Peter Zijlstra <> | Date | Wed, 02 Apr 2008 13:08:56 +0200 |
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On Wed, 2008-04-02 at 13:07 +0200, Jens Axboe wrote: > 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.
but what holds off the slab allocator re-issueing that same object and someone else writing other stuff into it?
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