Re: crash on connect

[Glauber Costa <glauber@scylladb.com>]

On Thu, Feb 20, 2020 at 12:28 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 2/20/20 9:52 AM, Glauber Costa wrote:
> > 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)
>
> Can't seem to hit it here, went through thousands of iterations...
> I'll keep trying.
>
> If you have time, you can try and enable CONFIG_KASAN=y and see if
> you can hit it with that.

sure thing. will let you know

>
> --
> Jens Axboe
>