Chris Leech <[EMAIL PROTECTED]> wrote:
>
There seems to be a small race here.
> +static void net_dma_rebalance(void)
> +{
> + unsigned int cpu, i, n;
> + struct dma_chan *chan;
> +
> + lock_cpu_hotplug();
> +
> + if (net_dma_count == 0) {
> + for_each_online_cpu(cpu)
> + rcu_assign_pointer(per_cpu(softnet_data.net_dma, cpu),
> NULL);
> + unlock_cpu_hotplug();
> + return;
> + }
If some other CPU does netdev_dma_event(DMA_RESOURCE_REMOVED) now
> + i = 0;
> + cpu = first_cpu(cpu_online_map);
> +
> + rcu_read_lock();
> + list_for_each_entry(chan, &net_dma_client->channels, client_node) {
> + n = ((num_online_cpus() / net_dma_count)
> + + (i < (num_online_cpus() % net_dma_count) ? 1 : 0));
This will get a divide-by-zero.
> + while(n) {
> + per_cpu(softnet_data.net_dma, cpu) = chan;
> + cpu = next_cpu(cpu, cpu_online_map);
> + n--;
> + }
> + i++;
> + }
> + rcu_read_unlock();
> +
> + unlock_cpu_hotplug();
> +}
> +
> +/**
> + * netdev_dma_event - event callback for the net_dma_client
> + * @client: should always be net_dma_client
> + * @chan:
> + * @event:
> + */
> +static void netdev_dma_event(struct dma_client *client, struct dma_chan
> *chan,
> + enum dma_event event)
> +{
> + switch (event) {
> + case DMA_RESOURCE_ADDED:
> + net_dma_count++;
> + net_dma_rebalance();
> + break;
> + case DMA_RESOURCE_REMOVED:
> + net_dma_count--;
> + net_dma_rebalance();
> + break;
> + default:
> + break;
> + }
> +}
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