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SubjectRe: [patch 1/4] kref: warn kref_put() with unreferenced kref
On Mon, Apr 24, 2006 at 04:33:34PM +0800, Akinobu Mita wrote:
> @@ -56,12 +57,13 @@ int kref_put(struct kref *kref, void (*r
> * if current count is one, we are the last user and can release object
> * right now, avoiding an atomic operation on 'refcount'
> */
> - if ((atomic_read(&kref->refcount) == 1) ||
> - (atomic_dec_and_test(&kref->refcount))) {
> - release(kref);
> - return 1;
> - }
> - return 0;
> + if (atomic_read(&kref->refcount) == 1)
> + atomic_set(&kref->refcount, 0);
> + else if (!atomic_dec_and_test(&kref->refcount))
> + return 0;

This is WRONG. The refcount can be incremented (to two) AFTER the
atomic_read ==1 and the "atomic_set". The original code seems
ok in this respect.

Roger.


--
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