From 58fdffe2919da9ef566f073ce8f04508157a6199 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20B=C3=BChler?= <source@stbuehler.de>
Date: Thu, 15 Apr 2021 17:31:00 +0800
Subject: [PATCH] io_uring: remove unnecessary barrier after unsetting
 IORING_SQ_NEED_WAKEUP
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mainline inclusion
from mainline-5.1
commit 62977281a6384d3904c02272a638cc3ac3bac54d
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

There is no operation to order with afterwards, and removing the flag is
not critical in any way.

There will always be a "race condition" where the application will
trigger IORING_ENTER_SQ_WAKEUP when it isn't actually needed.

Signed-off-by: Stefan Bühler <source@stbuehler.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: yangerkun <yangerkun@huawei.com>
Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
---
 fs/io_uring.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0a0fbb236147..a3a78d3cab7a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1966,13 +1966,11 @@ static int io_sq_thread(void *data)
 				finish_wait(&ctx->sqo_wait, &wait);
 
 				ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP;
-				smp_wmb();
 				continue;
 			}
 			finish_wait(&ctx->sqo_wait, &wait);
 
 			ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP;
-			smp_wmb();
 		}
 
 		i = 0;
-- 
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