Commit c57a91fb authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: fix missing mb() before waitqueue_active 



In case of !SQPOLL, io_cqring_ev_posted_iopoll() doesn't provide a
memory barrier required by waitqueue_active(&ctx->poll_wait). There is
a wq_has_sleeper(), which does smb_mb() inside, but it's called only for
SQPOLL.

Fixes: 5fd46178 ("io_uring: be smarter about waking multiple CQ ring waiters")
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2982e53bcea2274006ed435ee2a77197107d8a29.1631130542.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 713b9825

fs/io_uring.c

+4 −1
Original line number Diff line number Diff line
@@ -1619,8 +1619,11 @@ 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 (wq_has_sleeper(&ctx->cq_wait))

		if (waitqueue_active(&ctx->cq_wait))

			wake_up_all(&ctx->cq_wait);

	}

	if (io_should_trigger_evfd(ctx))