[PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

[PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

[Caleb Sander Mateos]

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

RE: [PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

[lizetao]

Hi,

> -----Original Message-----
> From: Caleb Sander Mateos <csander@purestorage.com>
> Sent: Wednesday, February 12, 2025 8:51 AM
> To: Jens Axboe <axboe@kernel.dk>; Pavel Begunkov <asml.silence@gmail.com>
> Cc: Caleb Sander Mateos <csander@purestorage.com>; io-
> uring@vger.kernel.org; linux-kernel@vger.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@purestorage.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@huawei.com>

---
Li Zetao

Re: [PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

[Caleb Sander Mateos]

Hi Jens,
Gentle ping on this patch that Li Zetao reviewed last week. Do you
think the comment should be removed/reworded to match the new if
condition?

Thanks,
Caleb

On Tue, Feb 11, 2025 at 4:51 PM Caleb Sander Mateos
<csander@purestorage.com> wrote:
>
> 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@purestorage.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) {
>                 req->io_task_work.func = io_req_task_complete;
>                 io_req_task_work_add(req);
>                 return;
>         }
>
> --
> 2.45.2
>

Re: [PATCH] io_uring: use lockless_cq flag in io_req_complete_post()

[Jens Axboe]

On Tue, 11 Feb 2025 17:51:18 -0700, Caleb Sander Mateos wrote:
> 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().
> 
> 

Applied, thanks!

[1/1] io_uring: use lockless_cq flag in io_req_complete_post()
      commit: 62aa9805d123165102273eb277f776aaca908e0e

Best regards,
-- 
Jens Axboe