Re: [PATCH] io_uring: add support for multishot timeouts

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

On 3/23/23 23:10, David Wei wrote:
> A multishot timeout submission will repeatedly generate completions with
> the IORING_CQE_F_MORE cflag set. Depending on the value of the `off' field
> in the submission, these timeouts can either repeat indefinitely until
> cancelled (`off' = 0) or for a fixed number of times (`off' > 0).
> 
> Only noseq timeouts (i.e. not dependent on the number of I/O
> completions) are supported.

It's ok, I'm not sure there is anyone using sequences

> For the second case, the `target_seq' field in `struct io_timeout' is
> re-purposed to track the remaining number of timeouts.

We have space in struct io_timeout, let's just add another
field there.

[...]
>   static bool io_kill_timeout(struct io_kiocb *req, int status)
>   	__must_hold(&req->ctx->timeout_lock)
>   {
> @@ -202,6 +215,13 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
>   	struct io_ring_ctx *ctx = req->ctx;
>   	unsigned long flags;
>   
> +	if (!io_timeout_finish(timeout, data)) {
> +		io_aux_cqe(req->ctx, false, req->cqe.user_data, -ETIME,
> +			   IORING_CQE_F_MORE, true);

We can't post a cqe from here, it should be a task context,
e.g. using tw

> +		hrtimer_forward_now(&data->timer, timespec64_to_ktime(data->ts));
> +		return HRTIMER_RESTART;
> +	}
> +
[...]

-- 
Pavel Begunkov