This Linux kernel change "io_uring: remove unnecessary barrier before reading SQ tail" is included in the Linux 5.1 release. This change is authored by Stefan Bühler <source [at] stbuehler.de> on Wed Apr 24 23:54:20 2019 +0200. The commit for this change in Linux stable tree is 82ab082 (patch).
io_uring: remove unnecessary barrier before reading SQ tail There is no operation before to order with. 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 d3c57ee..662f1c0 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1831,8 +1831,6 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) * though the application is the one updating it. */ head = ctx->cached_sq_head; - /* See comment at the top of this file */ - smp_rmb(); /* make sure SQ entry isn't read before tail */ if (head == smp_load_acquire(&ring->r.tail)) return false;