Messages in this thread Patch in this message | | | Date | Wed, 2 Apr 2008 09:08:09 -0700 | From | "Paul E. McKenney" <> | Subject | Re: kmemcheck caught read from freed memory (cfq_free_io_context) |
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On Wed, Apr 02, 2008 at 02:01:13PM +0300, 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.
Would the following be an appropriate fix? It seems to me to be in the same spirit as the existing check for s->ctor.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> ---
slub_kmemcheck.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/slub_kmemcheck.c b/mm/slub_kmemcheck.c index 8620a8b..e07f62a 100644 --- a/mm/slub_kmemcheck.c +++ b/mm/slub_kmemcheck.c @@ -93,6 +93,6 @@ kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object) void kmemcheck_slab_free(struct kmem_cache *s, void *object) { - if (!s->ctor) + if (!s->ctor && !(s->flags & SLAB_DESTROY_BY_RCU)) kmemcheck_mark_freed(object, s->objsize); }
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