Re: [PATCH net-next v11 10/21] net: add helpers for setting a memory provider on an rx queue

[Pavel Begunkov <asml.silence@gmail.com>]

On 1/17/25 02:25, Jakub Kicinski wrote:
> On Thu, 16 Jan 2025 15:16:52 -0800 David Wei wrote:
>> +static void __net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
>> +			      struct pp_memory_provider_params *old_p)
>> +{
>> +	struct netdev_rx_queue *rxq;
>> +	int ret;
>> +
>> +	if (WARN_ON_ONCE(ifq_idx >= dev->real_num_rx_queues))
>> +		return;
>> +
>> +	rxq = __netif_get_rx_queue(dev, ifq_idx);
> 
> I think there's a small race between io_uring closing and the netdev
> unregister. We can try to uninstall twice, let's put

They're gated by checking ifq->netdev in io_uring code, which is
cleared by them under a spin. So either io_uring does
__net_mp_close_rxq() and ->uninstall does nothing, or vise versa.

> 	/* Callers holding a netdev ref may get here after we already
> 	 * went thru shutdown via dev_memory_provider_uninstall().
> 	 */
> 	if (dev->reg_state > NETREG_REGISTERED &&
> 	    !rxq->mp_params.mp_ops)
> 		return;
> 
> here, and in dev_memory_provider_uninstall() clear the pointers?
> 
>> +	if (WARN_ON_ONCE(rxq->mp_params.mp_ops != old_p->mp_ops ||
>> +			 rxq->mp_params.mp_priv != old_p->mp_priv))
>> +		return;
>> +
>> +	rxq->mp_params.mp_ops = NULL;
>> +	rxq->mp_params.mp_priv = NULL;
>> +	ret = netdev_rx_queue_restart(dev, ifq_idx);
>> +	if (ret)
>> +		pr_devel("Could not restart queue %u after removing memory provider.\n",
>> +			 ifq_idx);
>> +}

-- 
Pavel Begunkov