io_uring: remove unnecessary barrier after updating SQ head [Linux 5.1]

io_uring: remove unnecessary barrier after updating SQ head [Linux 5.1]

This Linux kernel change "io_uring: remove unnecessary barrier after updating SQ head" is included in the Linux 5.1 release. This change is authored by Stefan Bühler <source [at] stbuehler.de> on Wed Apr 24 23:54:19 2019 +0200. The commit for this change in Linux stable tree is 9e4c15a (patch).

io_uring: remove unnecessary barrier after updating SQ head

There is no operation afterwards to order with.

Signed-off-by: Stefan Bühler <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 fs/io_uring.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3671a65..d3c57ee 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1798,12 +1798,6 @@ static void io_commit_sqring(struct io_ring_ctx *ctx)
         * write new data to them.
         */
        smp_store_release(&ring->r.head, ctx->cached_sq_head);
-
-       /*
-        * write side barrier of head update, app has read side. See
-        * comment at the top of this file
-        */
-       smp_wmb();
    }
 }

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