Re: [PATCH] io_uring/cmd_net: prevent infinite retry loop on unextractable timestamp skb

[Pavel Begunkov]

n 10/8/26 15:59, Bui Viet Dung wrote:
> On Thu, Oct 8, 2026 at 3:43 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
> > Sounds fine since there are only timestamp skbs in this list, do
> > you have a test case?
>
> Hi Pavel,
>
> Thanks for the review.
>
> The issue was spotted during code inspection of the error handling path
> in io_uring_cmd_timestamp(): specifically when skb_get_tx_timestamp() returns
> a negative error (e.g. -ENOENT due to missing PHC bindings with
> SOF_TIMESTAMPING_BIND_PHC or unavailable timestamp data). Since the
> multishot apoll remains armed on EPOLLERR and the unhandled skb is spliced
> back onto the head of sk_error_queue, it immediately re-triggers the command
> in a tight busy-loop.
>
> Below is a standalone test program demonstrating the TX_TIMESTAMP command
> setup and execution with CQE32:

Did you actually reproduce it? This program doesn't for me, nor does
fault injection. Taking a look at the code, io_uring_cmd_timestamp()
returns -EAGAIN, and the request will wait for the next wake up in the
polling code. There are bits to improve, but that's not an infinite loop.

--
Pavel Begunkov