Chris Leech <[email protected]> wrote:
>
> +/**
> + * dma_client_chan_free - release a DMA channel
> + * @chan: &dma_chan
> + */
> +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);
> + chan->client = NULL;
> + kref_put(&chan->device->refcount, dma_async_device_cleanup);
> +}
> +
> +static void dma_chan_free_rcu(struct rcu_head *rcu)
> +{
> + struct dma_chan *chan = container_of(rcu, struct dma_chan, rcu);
> + int bias = 0x7FFFFFFF;
> + int i;
> + for_each_cpu(i)
> + bias -= local_read(&per_cpu_ptr(chan->local, i)->refcount);
> + atomic_sub(bias, &chan->refcount.refcount);
> + kref_put(&chan->refcount, dma_chan_cleanup);
> +}
> +
> +static void dma_client_chan_free(struct dma_chan *chan)
> +{
> + atomic_add(0x7FFFFFFF, &chan->refcount.refcount);
> + chan->slow_ref = 1;
> + call_rcu(&chan->rcu, dma_chan_free_rcu);
> +}
A comment describing this `bias' magic would be nice.
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