Commit 4f7067c3 authored by Stefan Bühler's avatar Stefan Bühler Committed by Jens Axboe
Browse files

io_uring: remove unnecessary barrier before wq_has_sleeper 



wq_has_sleeper has a full barrier internally. The smp_rmb barrier in
io_uring_poll synchronizes with it.

Signed-off-by: default avatarStefan Bühler <source@stbuehler.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 1e84b97b

fs/io_uring.c

+4 −7
Original line number Diff line number Diff line
@@ -418,12 +418,6 @@ static void io_commit_cqring(struct io_ring_ctx *ctx) 
		/* order cqe stores with ring update */

		smp_store_release(&ring->r.tail, ctx->cached_cq_tail);



		/*

		 * Write sider barrier of tail update, app has read side. See

		 * comment at the top of this file.

		 */

		smp_wmb();



		if (wq_has_sleeper(&ctx->cq_wait)) {

			wake_up_interruptible(&ctx->cq_wait);

			kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
@@ -2677,7 +2671,10 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) 
	__poll_t mask = 0;



	poll_wait(file, &ctx->cq_wait, wait);

	/* See comment at the top of this file */

	/*

	 * synchronizes with barrier from wq_has_sleeper call in

	 * io_commit_cqring

	 */

	smp_rmb();

	if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head !=

	    ctx->sq_ring->ring_entries)