Re: [PATCH] io_uring/cmd_net: end TX_TIMESTAMP multishot when the CQ is full

[Pavel Begunkov]

On 9/27/26 08:42, lollipopkit wrote:
> SOCKET_URING_OP_TX_TIMESTAMP arms an EPOLLERR apoll multishot and, on
> each error queue edge, posts one 32 byte aux CQE per timestamp skb. Aux
> CQEs have no overflow backing, so io_uring_cmd_post_mshot_cqe32() fails
> once the CQ ring is full. The loop then stops, splices the unprocessed
> skbs back onto sk_error_queue and returns -EAGAIN.
...>   static int io_uring_cmd_timestamp(struct socket *sock,
> @@ -135,7 +137,8 @@ static int io_uring_cmd_timestamp(struct socket *sock,
>   		skb = skb_peek(&list);
>   		if (!skb)
>   			break;
> -		if (!io_process_timestamp_skb(cmd, sk, skb, issue_flags))
> +		ret = io_process_timestamp_skb(cmd, sk, skb, issue_flags);
> +		if (ret)
>   			break;
>   		__skb_dequeue(&list);
>   		consume_skb(skb);
> @@ -145,6 +148,12 @@ static int io_uring_cmd_timestamp(struct socket *sock,
>   		scoped_guard(spinlock_irqsave, &q->lock)
>   			skb_queue_splice(&list, q);
>   	}
> +	/*
> +	 * Aux CQEs cannot overflow and the poll is edge triggered, so nothing
> +	 * re-runs the command once the CQ drains. End the multishot instead.
> +	 */
> +	if (ret == -ENOBUFS)
> +		return -ENOBUFS;

I'd make it a 3-state return instead of relying on
skb_get_tx_timestamp() not returning specific error codes, but it
should be fine for now.

Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx>

>   	return -EAGAIN;
>   }
>   
>
> base-commit: a3bdf68feecc57af5c11fb599f860ac9790ffad9

--
Pavel Begunkov