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[for-next,2/4] io_uring: don't race double poll setting REQ_F_ASYNC_DATA

Message ID df6920f509c11115aa2bce8b34dc5fdb0eb98920.1657203020.git.asml.silence@gmail.com (mailing list archive)
State New
Headers show
Series poll locking fixes | expand

Commit Message

Pavel Begunkov July 7, 2022, 2:13 p.m. UTC 
Just as with io_poll_double_prepare() setting REQ_F_DOUBLE_POLL, we can
race with the first poll entry when setting REQ_F_ASYNC_DATA. Move it
under io_poll_double_prepare().

Fixes: a18427bb2d9b ("io_uring: optimise submission side poll_refs")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/poll.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
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Patch

diff --git a/io_uring/poll.c b/io_uring/poll.c
index 3710a0a46a87..c1359d45a396 100644
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -410,6 +410,8 @@  static void io_poll_double_prepare(struct io_kiocb *req)
 		spin_lock_irq(&head->lock);
 
 	req->flags |= REQ_F_DOUBLE_POLL;
+	if (req->opcode == IORING_OP_POLL_ADD)
+		req->flags |= REQ_F_ASYNC_DATA;
 
 	if (head)
 		spin_unlock_irq(&head->lock);
@@ -448,13 +450,11 @@  static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt,
 			return;
 		}
 
-		io_poll_double_prepare(req);
 		/* mark as double wq entry */
 		wqe_private |= IO_WQE_F_DOUBLE;
 		io_init_poll_iocb(poll, first->events, first->wait.func);
+		io_poll_double_prepare(req);
 		*poll_ptr = poll;
-		if (req->opcode == IORING_OP_POLL_ADD)
-			req->flags |= REQ_F_ASYNC_DATA;
 	} else {
 		/* fine to modify, there is no poll queued to race with us */
 		req->flags |= REQ_F_SINGLE_POLL;