From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 27 Feb 2020 02:54:12 +0000 (-0700)
Subject: io_uring: we should not need two write barriers for SQ updates
X-Git-Tag: fio-3.19~7
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=58d3994d9be0783990af82571cea819b499d526c

io_uring: we should not need two write barriers for SQ updates

Just after updating the tail should be fine.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/engines/io_uring.c b/engines/io_uring.c
index 5e59f975..1efc6cff 100644
--- a/engines/io_uring.c
+++ b/engines/io_uring.c
@@ -374,8 +374,6 @@ static enum fio_q_status fio_ioring_queue(struct thread_data *td,
 	if (next_tail == *ring->head)
 		return FIO_Q_BUSY;
 
-	/* ensure sqe stores are ordered with tail update */
-	write_barrier();
 	if (o->cmdprio_percentage)
 		fio_ioring_prio_prep(td, io_u);
 	ring->array[tail & ld->sq_ring_mask] = io_u->index;
diff --git a/t/io_uring.c b/t/io_uring.c
index 55b75f6e..e84a2b6b 100644
--- a/t/io_uring.c
+++ b/t/io_uring.c
@@ -216,8 +216,6 @@ static int prep_more_ios(struct submitter *s, int max_ios)
 	} while (prepped < max_ios);
 
 	if (*ring->tail != tail) {
-		/* order tail store with writes to sqes above */
-		write_barrier();
 		*ring->tail = tail;
 		write_barrier();
 	}