linux-kernel - [PATCH v2 5/8] io_uring: inline llist

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Message-Id: <f0165493af7b379943c792114b972f331e7d7d10.1680782017.git.asml.silence@gmail.com>
Date:   Thu,  6 Apr 2023 14:20:11 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, asml.silence@...il.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/8] io_uring: inline llist_add()

We'll need to grab some information from the previous request in the tw
list, inline llist_add(), it'll be used in the following patch.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 io_uring/io_uring.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 6f175fe682e4..786ecfa01c54 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1303,8 +1303,15 @@ static __cold void io_fallback_tw(struct io_uring_task *tctx)
 static void io_req_local_work_add(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
+	struct llist_node *first;
 
-	if (!llist_add(&req->io_task_work.node, &ctx->work_llist))
+	first = READ_ONCE(ctx->work_llist.first);
+	do {
+		req->io_task_work.node.next = first;
+	} while (!try_cmpxchg(&ctx->work_llist.first, &first,
+			      &req->io_task_work.node));
+
+	if (first)
 		return;
 
 	/* needed for the following wake up */
-- 
2.40.0