> There is a change of behaviour, if IORING_FEAT_EXT_ARG is set it > won't submit (IIRC, since 5.12) -- it's pretty important for some > multi-threaded cases. > > So... where in particular does it say that? In case your liburing > is up to date and we forgot to remove such a comment. https://github.com/axboe/liburing/blob/c96202546bd9d7420d97bc05e73c7144d0924e8a/src/queue.c#L269 "For kernels without IORING_FEAT_EXT_ARG (5.10 and older), if 'ts' is specified, the application need not call io_uring_submit() before calling this function, as we will do that on its behalf." and I'm using the latest Clear Linux kernel which is 5.10, so that's why I wasn't submitting.