Re: [patch 1/4] kref: warn kref_put() with unreferenced kref

[Rogier Wolff <R.E.Wolff@BitWizard.nl>]

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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