Commit 0f847471 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: remove extra barrier for non-sqpoll iopoll 



smp_mb() in io_cqring_ev_posted_iopoll() is only there because of
waitqueue_active(). However, non-SQPOLL IOPOLL ring doesn't wake the CQ
and so the barrier there is useless. Kill it, it's usually pretty
expensive.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d72e8ef6f7a3f6a72e18fad8409f7d47afc8da7d.1647481208.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b91ef187

fs/io_uring.c

+1 −4
Original line number Diff line number Diff line
@@ -1877,11 +1877,8 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx) 


static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)

{

	/* see waitqueue_active() comment */

	smp_mb();



	if (ctx->flags & IORING_SETUP_SQPOLL) {

		if (waitqueue_active(&ctx->cq_wait))

		if (wq_has_sleeper(&ctx->cq_wait))

			wake_up_all(&ctx->cq_wait);

	}

	io_eventfd_signal(ctx);