Re: recvmsg not honoring O_NONBLOCK

[Hrvoje Zeba <zeba.hrvoje@gmail.com>]

On Sat, Jul 9, 2022 at 11:26 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 7/9/22 8:21 AM, Hrvoje Zeba wrote:
> > Hi folks,
> >
> > I was adapting msquic library to work with iouring and found an issue
> > with recvmsg() where it ignores O_NONBLOCK flag set on the file
> > descriptor. If MSG_DONTWAIT is set in flags, it behaves as expected.
> > I've attached a simple test which currently just hangs on iouring's
> > recvmsg(). I'm guessing sendmsg() behaves the same way but I have no
> > idea how to fill the buffer to reliably test it.
>
> I am guessing that you're waiting off waiting for the event. It's not
> stalled on the issue, it'll arm poll and wait for an event. I won't go
> into too much of a ran on O_NONBLOCK, but it's a giant mess, and where
> possible, io_uring relies on per-request non-block flags as that is much
> saner behavior.
>

Oh, this is intentional behaviour. Got it! Thanks for the explanation.

-- 
I doubt, therefore I might be.