From: Stefan Bühler <source@stbuehler.de>
Date: Wed, 24 Apr 2019 21:54:22 +0000 (+0200)
Subject: io_uring: remove unnecessary barrier after unsetting IORING_SQ_NEED_WAKEUP
X-Git-Tag: v5.1~12^2~7
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=62977281a6384d3904c02272a638cc3ac3bac54d;p=users%2Fhch%2Fblock.git

io_uring: remove unnecessary barrier after unsetting IORING_SQ_NEED_WAKEUP

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>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2ebc33cc907b..77b247b5d10b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1969,13 +1969,11 @@ 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;