Commit b1445e59 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: synchronise ev_posted() with waitqueues 



waitqueue_active() needs smp_mb() to be in sync with waitqueues
modification, but we miss it in io_cqring_ev_posted*() apart from
cq_wait() case.

Take an smb_mb() out of wq_has_sleeper() making it waitqueue_active(),
and place it a few lines before, so it can synchronise other
waitqueue_active() as well.

The patch doesn't add any additional overhead, so even if there are
no problems currently, it's just safer to have it this way.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4aa84f2f

fs/io_uring.c

+8 −2
Original line number Diff line number Diff line
@@ -1700,13 +1700,16 @@ static inline unsigned __io_cqring_events(struct io_ring_ctx *ctx) 


static void io_cqring_ev_posted(struct io_ring_ctx *ctx)

{

	/* see waitqueue_active() comment */

	smp_mb();



	if (waitqueue_active(&ctx->wait))

		wake_up(&ctx->wait);

	if (ctx->sq_data && waitqueue_active(&ctx->sq_data->wait))

		wake_up(&ctx->sq_data->wait);

	if (io_should_trigger_evfd(ctx))

		eventfd_signal(ctx->cq_ev_fd, 1);

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

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

		wake_up_interruptible(&ctx->cq_wait);

		kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);

	}
@@ -1714,13 +1717,16 @@ 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->wait))

			wake_up(&ctx->wait);

	}

	if (io_should_trigger_evfd(ctx))

		eventfd_signal(ctx->cq_ev_fd, 1);

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

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

		wake_up_interruptible(&ctx->cq_wait);

		kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);

	}