On Sun, Dec 20, 2020 at 7:59 AM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote: > > On 20/12/2020 00:25, Jens Axboe wrote: > > On 12/19/20 4:42 PM, Pavel Begunkov wrote: > >> On 19/12/2020 23:13, Jens Axboe wrote: > >>> On 12/19/20 2:54 PM, Jens Axboe wrote: > >>>> On 12/19/20 1:51 PM, Josef wrote: > >>>>>> And even more so, it's IOSQE_ASYNC on the IORING_OP_READ on an eventfd > >>>>>> file descriptor. You probably don't want/mean to do that as it's > >>>>>> pollable, I guess it's done because you just set it on all reads for the > >>>>>> test? > >>>>> > >>>>> yes exactly, eventfd fd is blocking, so it actually makes no sense to > >>>>> use IOSQE_ASYNC > >>>> > >>>> Right, and it's pollable too. > >>>> > >>>>> I just tested eventfd without the IOSQE_ASYNC flag, it seems to work > >>>>> in my tests, thanks a lot :) > >>>>> > >>>>>> In any case, it should of course work. This is the leftover trace when > >>>>>> we should be exiting, but an io-wq worker is still trying to get data > >>>>>> from the eventfd: > >>>>> > >>>>> interesting, btw what kind of tool do you use for kernel debugging? > >>>> > >>>> Just poking at it and thinking about it, no hidden magic I'm afraid... > >>> > >>> Josef, can you try with this added? Looks bigger than it is, most of it > >>> is just moving one function below another. > >> > >> Hmm, which kernel revision are you poking? Seems it doesn't match > >> io_uring-5.10, and for 5.11 io_uring_cancel_files() is never called with > >> NULL files. > >> > >> if (!files) > >> __io_uring_cancel_task_requests(ctx, task); > >> else > >> io_uring_cancel_files(ctx, task, files); > > > > Yeah, I think I messed up. If files == NULL, then the task is going away. > > So we should cancel all requests that match 'task', not just ones that > > match task && files. > > > > Not sure I have much more time to look into this before next week, but > > something like that. > > > > The problem case is the async worker being queued, long before the task > > is killed and the contexts go away. But from exit_files(), we're only > > concerned with canceling if we have inflight. Doesn't look right to me. > > In theory all that should be killed in io_ring_ctx_wait_and_kill(), > of course that's if the ring itself is closed. > > Guys, do you share rings between processes? Explicitly like sending > io_uring fd over a socket, or implicitly e.g. sharing fd tables > (threads), or cloning with copying fd tables (and so taking a ref > to a ring). We do not share rings between processes. Our rings are accessible from different threads (under locks), but nothing fancy. > In other words, if you kill all your io_uring applications, does it > go back to normal? I'm pretty sure it does not, the only fix is to reboot the box. But I'll find an affected box and double check just in case. -- Dmitry Kadashev
