linux-kernel - RE: [PATCH] io_uring: use lockless_cq flag in io_req_complete

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Message-ID: <acc4f93c55574b8abd55da174248e9d2@huawei.com>
Date: Thu, 13 Feb 2025 14:04:28 +0000
From: lizetao <lizetao1@...wei.com>
To: Caleb Sander Mateos <csander@...estorage.com>
CC: "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jens Axboe
	<axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>
Subject: RE: [PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

Hi,

> -----Original Message-----
> From: Caleb Sander Mateos <csander@...estorage.com>
> Sent: Wednesday, February 12, 2025 8:51 AM
> To: Jens Axboe <axboe@...nel.dk>; Pavel Begunkov <asml.silence@...il.com>
> Cc: Caleb Sander Mateos <csander@...estorage.com>; io-
> uring@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] io_uring: use lockless_cq flag in io_req_complete_post()
> 
> io_uring_create() computes ctx->lockless_cq as:
> ctx->task_complete || (ctx->flags & IORING_SETUP_IOPOLL)
> 
> So use it to simplify that expression in io_req_complete_post().
> 
> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
> ---
>  io_uring/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index
> ec98a0ec6f34..0bd94599df81 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -897,11 +897,11 @@ static void io_req_complete_post(struct io_kiocb
> *req, unsigned issue_flags)
> 
>  	/*
>  	 * Handle special CQ sync cases via task_work. DEFER_TASKRUN
> requires
>  	 * the submitter task context, IOPOLL protects with uring_lock.
>  	 */
> -	if (ctx->task_complete || (ctx->flags & IORING_SETUP_IOPOLL)) {
> +	if (ctx->lockless_cq) {

When the completion_lock is not held, the req completion event needs to be handled through
the task_work mechanism, so this modification makes sense to me.

>  		req->io_task_work.func = io_req_task_complete;
>  		io_req_task_work_add(req);
>  		return;
>  	}
> 
> --
> 2.45.2
> 

Reviewed-by: Li Zetao <lizetao1@...wei.com>

---
Li Zetao