Re: [PATCH] DMA: Fix broken device refcounting

[Haavard Skinnemoen <hskinnemoen@atmel.com>]

On Fri, 26 Oct 2007 09:36:17 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> @@ -221,7 +220,6 @@ void dma_chan_cleanup(struct kref *kref)
>  {
>  	struct dma_chan *chan = container_of(kref, struct dma_chan, refcount);
>	chan->device->device_free_chan_resources(chan);
> -	kref_put(&chan->device->refcount, dma_async_device_cleanup);
>  }
>  EXPORT_SYMBOL(dma_chan_cleanup);

While I can't see any problems with the rest of the patch, I think this
part is wrong for the same reasons removing the kref_put() from the
class device cleanup function is. I don't see any constraint that
guarantees that dma_chan_cleanup() will always be called before
dma_dev_release(), which means that "chan" may have been freed before
this function gets a chance to run. Please correct me if I'm wrong.

Håvard