Hi I've been trying to make sense of some weird behavior with the seastar implementation of io_uring, and started to suspect a bug in io_uring's connect. The situation is as follows: - A connect() call is issued (and in the backend I can choose if I use uring or not) - The connection is supposed to take a while to establish. - I call shutdown on the file descriptor If io_uring is not used: - connect() starts by returning EINPROGRESS as expected, and after the shutdown the file descriptor is finally made ready for epoll. I call getsockopt(SOL_SOCKET, SO_ERROR), and see the error (104) if io_uring is used: - if the SQE has the IOSQE_ASYNC flag on, connect() never returns. - if the SQE *does not* have the IOSQE_ASYNC flag on, then most of the time the test works as intended and connect() returns 104, but occasionally it hangs too. Note that, seastar may choose not to call io_uring_enter immediately and batch sqes. Sounds like some kind of race? I know C++ probably stinks like the devil for you guys, but if you are curious to see the code, this fails one of our unit tests: https://github.com/scylladb/seastar/blob/master/tests/unit/connect_test.cc See test_connection_attempt_is_shutdown (above is the master seastar tree, not including the io_uring implementation) Please let me know if this rings a bell and if there is anything I should be verifying here
