From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sun, 28 Feb 2021 22:04:54 +0000 (+0000)
Subject: io_uring: replace cmpxchg in fallback with xchg
X-Git-Tag: baikal/mips/sdk5.9~11393^2~21
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=3ec82f5e319969112f4274cfcf794f9bd2cb1647;p=kernel.git

io_uring: replace cmpxchg in fallback with xchg

io_run_ctx_fallback() can use xchg() instead of cmpxchg(). It's simpler
and faster.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 62a73543ab864..57c7833ba62be 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8484,15 +8484,11 @@ static int io_remove_personalities(int id, void *p, void *data)
 
 static bool io_run_ctx_fallback(struct io_ring_ctx *ctx)
 {
-	struct callback_head *work, *head, *next;
+	struct callback_head *work, *next;
 	bool executed = false;
 
 	do {
-		do {
-			head = NULL;
-			work = READ_ONCE(ctx->exit_task_work);
-		} while (cmpxchg(&ctx->exit_task_work, work, head) != work);
-
+		work = xchg(&ctx->exit_task_work, NULL);
 		if (!work)
 			break;