Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 24 Apr 2006 22:09:51 -0700 | From | Greg KH <> | Subject | Re: [patch 1/4] kref: warn kref_put() with unreferenced kref |
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On Tue, Apr 25, 2006 at 12:34:10PM +0800, Akinobu Mita wrote: > On Mon, Apr 24, 2006 at 08:51:28PM -0700, Greg KH wrote: > > > @@ -49,6 +49,7 @@ void kref_get(struct kref *kref) > > > */ > > > int kref_put(struct kref *kref, void (*release)(struct kref *kref)) > > > { > > > + WARN_ON(atomic_read(&kref->refcount) < 1); > > > > How can this ever be true? If the refcount _ever_ goes below 1, the > > object is freed. > > The idea of detection kref_put() with unreferenced object was stolen > from BUG_ON()es in blocks/ll_rw_blk.c and fs/bio.c > > ll_rw_blk.c: BUG_ON(atomic_read(&ioc->refcount) == 0); > > bio.c: BIO_BUG_ON(!atomic_read(&bio->bi_cnt)); > > But the kref counter usually does not become zero. Because kref is > trying to reduce the number of atomic_dec_and_test() > > So this patch also set kref counter to zero here: > > > > + if (atomic_read(&kref->refcount) == 1) > > > + atomic_set(&kref->refcount, 0);
But again, if this happens the memory will be freed. So again, CONFIG_DEBUG_SLAB will catch this kind of thing.
Is there some reason you created these patches? Were you trying to debug something that was tracked down to a kref issue?
thanks,
greg k-h - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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