io_uring: remove unnecessary barrier after incrementing dropped counter [Linux 5.1]

io_uring: remove unnecessary barrier after incrementing dropped counter [Linux 5.1]

This Linux kernel change "io_uring: remove unnecessary barrier after incrementing dropped counter" is included in the Linux 5.1 release. This change is authored by Stefan Bühler <source [at] stbuehler.de> on Wed Apr 24 23:54:21 2019 +0200. The commit for this change in Linux stable tree is b841f19 (patch).

io_uring: remove unnecessary barrier after incrementing dropped counter

smp_store_release in io_commit_sqring already orders the store to
dropped before the update to SQ head.

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

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 fs/io_uring.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 662f1c0..2ebc33c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1846,8 +1846,6 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
    /* drop invalid entries */
    ctx->cached_sq_head++;
    ring->dropped++;
-   /* See comment at the top of this file */
-   smp_wmb();
    return false;
 }

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