On Fri, 1 Jun 2007 21:45:15 -0700 (PDT) Christoph Lameter <[email protected]> wrote:
> On Fri, 1 Jun 2007, Andrew Morton wrote:
>
> > They are different instances which happen to have the same length (zero).
>
> I guess one could use the slab allocators as a type of reservation
> ticket generator with zero sized objects. Hmmm.... But is that really a
> useful thing to do?
>
> > But the code will incorrectly decide that they are the same instance. It
> > might cause refcounting or accounting errors, for example. I don't know - the
> > kernel's a big place.
>
> That would have to occur with objects that are repeatedly allocated and
> then linked toghether etc. Linking typicallty requires a listhead so its
> typically difficult to do zero length objects.
Well I can't immediately think of a scenario in which it's likely to occur,
but we're in the position of trying to prove a negative.
Poke Bill Irwin - he'll think of something ;)
> > I agree the risk is low, but if something _does_ blow up, it will do so subtly.
>
> The cases that we have seen so far are due to array allocations of N
> elements where N == 0 leads to the creation of a zero sized object.
> The objects of the array are not zero sized it is just that zero of
> them are allocated.
We lose leak-detection and double-free detection this way, too. Not a big
deal.
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