Re: "Cannot allocate memory" on ring creation (not RLIMIT_MEMLOCK)

[Josef <josef.grieb@gmail.com>]

> I'd really appreciate if you can try one more. I want to know why
> the final cleanup doesn't cope  with it.

yeah sure, which kernel version? it seems to be that this patch
doesn't match io_uring-5.11 and io_uring-5.10

On Sun, 20 Dec 2020 at 15:22, Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 20/12/2020 13:00, Pavel Begunkov wrote:
> > On 20/12/2020 07:13, Josef wrote:
> >>> 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).
> >>
> >> no in netty we don't share ring between processes
> >>
> >>> In other words, if you kill all your io_uring applications, does it
> >>> go back to normal?
> >>
> >> no at all, the io-wq worker thread is still running, I literally have
> >> to restart the vm to go back to normal(as far as I know is not
> >> possible to kill kernel threads right?)
> >>
> >>> Josef, can you test the patch below instead? Following Jens' idea it
> >>> cancels more aggressively when a task is killed or exits. It's based
> >>> on [1] but would probably apply fine to for-next.
> >>
> >> it works, I run several tests with eventfd read op async flag enabled,
> >> thanks a lot :) you are awesome guys :)
> >
> > Thanks for testing and confirming! Either we forgot something in
> > io_ring_ctx_wait_and_kill() and it just can't cancel some requests,
> > or we have a dependency that prevents release from happening.
> >
> > BTW, apparently that patch causes hangs for unrelated but known
> > reasons, so better to not use it, we'll merge something more stable.
>
> I'd really appreciate if you can try one more. I want to know why
> the final cleanup doesn't cope  with it.
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 941fe9b64fd9..d38fc819648e 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8614,6 +8614,10 @@ static int io_remove_personalities(int id, void *p, void *data)
>         return 0;
>  }
>
> +static void io_cancel_defer_files(struct io_ring_ctx *ctx,
> +                                 struct task_struct *task,
> +                                 struct files_struct *files);
> +
>  static void io_ring_exit_work(struct work_struct *work)
>  {
>         struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
> @@ -8627,6 +8631,8 @@ static void io_ring_exit_work(struct work_struct *work)
>          */
>         do {
>                 io_iopoll_try_reap_events(ctx);
> +               io_poll_remove_all(ctx, NULL, NULL);
> +               io_kill_timeouts(ctx, NULL, NULL);
>         } while (!wait_for_completion_timeout(&ctx->ref_comp, HZ/20));
>         io_ring_ctx_free(ctx);
>  }
> @@ -8641,6 +8647,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
>                 io_cqring_overflow_flush(ctx, true, NULL, NULL);
>         mutex_unlock(&ctx->uring_lock);
>
> +       io_cancel_defer_files(ctx, NULL, NULL);
>         io_kill_timeouts(ctx, NULL, NULL);
>         io_poll_remove_all(ctx, NULL, NULL);
>
> --
> Pavel Begunkov



-- 
Josef