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Subject: Re: [PATCH 1/2] io_uring: trigger timeout after any sqe->off CQEs
To:     Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <cover.1587229607.git.asml.silence@gmail.com>
 <28005ea0de63e15dbffd87a49fe9b671f1afa87e.1587229607.git.asml.silence@gmail.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <88cbde3c-52a1-7fb3-c4a7-b548beaa5502@kernel.dk>
Date:   Mon, 20 Apr 2020 13:40:41 -0600
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On 4/18/20 11:20 AM, Pavel Begunkov wrote:
> +static void __io_flush_timeouts(struct io_ring_ctx *ctx)
> +{
> +	u32 end, start;
> +
> +	start = end = ctx->cached_cq_tail;
> +	do {
> +		struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
> +							struct io_kiocb, list);
> +
> +		if (req->flags & REQ_F_TIMEOUT_NOSEQ)
> +			break;
> +		/*
> +		 * multiple timeouts may have the same target,
> +		 * check that @req is in [first_tail, cur_tail]
> +		 */
> +		if (!io_check_in_range(req->timeout.target_cq, start, end))
> +			break;
> +
> +		list_del_init(&req->list);
> +		io_kill_timeout(req);
> +		end = ctx->cached_cq_tail;
> +	} while (!list_empty(&ctx->timeout_list));
> +}
> +
>  static void io_commit_cqring(struct io_ring_ctx *ctx)
>  {
>  	struct io_kiocb *req;
>  
> -	while ((req = io_get_timeout_req(ctx)) != NULL)
> -		io_kill_timeout(req);
> +	if (!list_empty(&ctx->timeout_list))
> +		__io_flush_timeouts(ctx);
>  
>  	__io_commit_cqring(ctx);
>  

Any chance we can do this without having to iterate timeouts on the
completion path?

-- 
Jens Axboe