On 4/27/19 9:50 AM, Stefan Bühler wrote: > Hi, > > On 24.04.19 00:07, Jens Axboe wrote: >> On 4/23/19 2:31 PM, Jens Axboe wrote: >>>> 1. An error for a submission should be returned as completion for that >>>> submission. Please don't break my main event loop with strange error >>>> codes just because a single operation is broken/not supported/... >>> >>> So that's the case I was referring to above. We can just make that change, >>> there's absolutely no reason to have errors passed back through a different >>> channel. >> >> Thinking about this a bit more, and I think the current approach is the >> best one. The issue is that only submission side events tied to an sqe >> can return an cqe, the rest have to be returned through the system call >> value. So I think it's cleaner to keep it as-is, honestly. > > Not sure we're talking about the same. > > I'm talking about the errors returned by io_submit_sqe: io_submit_sqes > (called by the SQ thread) calls io_cqring_add_event if there was an > error, but io_ring_submit (called by io_uring_enter) doesn't: instead, > if there were successfully submitted entries before, it will just return > those (and "undo" the current SQE), otherwise it will return the error, > which will then be returned by io_uring_enter. > > But if I get an error from io_uring_enter I have no idea whether it was > some generic error (say EINVAL for broken flags or EBADF for a > non-io-uring filedescriptor) or an error related to a single submission. > > I think io_ring_submit should call io_cqring_add_event on errors too > (like io_submit_sqes), and not stop handling submissions (and never > return an error). > > Maybe io_cqring_add_event could then even be moved to io_submit_sqe and > just return whether the job is already done or not (io_submit_sqes > returns the new "inflight" jobs, and io_ring_submit the total number of > submitted jobs). I think we are talking about the same thing, actually. See below patch. This changes it so that any error that occurs on behalf of a specific sqe WILL trigger a completion event, instead of returning it through io_uring_enter(). io_uring_enter() can still return -ERROR for errors that aren't specific to an sqe. I think this is what you had in mind? Totally untested, will do so now. -- Jens Axboe
