On Fri, Aug 7, 2020 at 1:57 AM Jens Axboe <axboe@xxxxxxxxx> wrote:
> An earlier commit:
>
> b7db41c9e03b ("io_uring: fix regression with always ignoring signals in io_cqring_wait()")
>
> ensured that we didn't get stuck waiting for eventfd reads when it's
> registered with the io_uring ring for event notification, but that didn't
> cover the general case of waiting on eventfd and having that dependency
> between io_uring and eventfd.
>
> Ensure that we use signaled notification for anything related to eventfd.
[...]
> @@ -1720,7 +1720,7 @@ static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb)
> */
> if (ctx->flags & IORING_SETUP_SQPOLL)
> notify = 0;
> - else if (ctx->cq_ev_fd)
> + else if (ctx->cq_ev_fd || (req->file && eventfd_file(req->file)))
> notify = TWA_SIGNAL;
Is the idea here that you want "polling an eventfd" to have different
UAPI semantics compared to e.g. "polling a pipe"? Or is there
something in-kernel that makes eventfds special?
