Re: crash on connect

[Glauber Costa <glauber@scylladb.com>]

On Thu, Feb 20, 2020 at 11:39 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 2/20/20 9:34 AM, Glauber Costa wrote:
> > On Thu, Feb 20, 2020 at 11:29 AM Jens Axboe <axboe@kernel.dk> wrote:
> >>
> >> On 2/20/20 9:17 AM, Jens Axboe wrote:
> >>> On 2/20/20 7:19 AM, Glauber Costa wrote:
> >>>> Hi there, me again
> >>>>
> >>>> Kernel is at 043f0b67f2ab8d1af418056bc0cc6f0623d31347
> >>>>
> >>>> This test is easier to explain: it essentially issues a connect and a
> >>>> shutdown right away.
> >>>>
> >>>> It currently fails due to no fault of io_uring. But every now and then
> >>>> it crashes (you may have to run more than once to get it to crash)
> >>>>
> >>>> Instructions are similar to my last test.
> >>>> Except the test to build is now "tests/unit/connect_test"
> >>>> Code is at git@github.com:glommer/seastar.git  branch io-uring-connect-crash
> >>>>
> >>>> Run it with ./build/release/tests/unit/connect_test -- -c1
> >>>> --reactor-backend=uring
> >>>>
> >>>> Backtrace attached
> >>>
> >>> Perfect thanks, I'll take a look!
> >>
> >> Haven't managed to crash it yet, but every run complains:
> >>
> >> got to shutdown of 10 with refcnt: 2
> >> Refs being all dropped, calling forget for 10
> >> terminate called after throwing an instance of 'fmt::v6::format_error'
> >>   what():  argument index out of range
> >> unknown location(0): fatal error: in "unixdomain_server": signal: SIGABRT (application abort requested)
> >>
> >> Not sure if that's causing it not to fail here.
> >
> > Ok, that means it "passed". (I was in the process of figuring out
> > where I got this wrong when I started seeing the crashes)
>
> Can you do, in your kernel dir:
>
> $ gdb vmlinux
> [...]
> (gdb) l *__io_queue_sqe+0x4a
>
> and see what it says?

0xffffffff81375ada is in __io_queue_sqe (fs/io_uring.c:4814).
4809 struct io_kiocb *linked_timeout;
4810 struct io_kiocb *nxt = NULL;
4811 int ret;
4812
4813 again:
4814 linked_timeout = io_prep_linked_timeout(req);
4815
4816 ret = io_issue_sqe(req, sqe, &nxt, true);
4817
4818 /*

(I am not using timeouts, just async_cancel)
>
> --
> Jens Axboe
>