Re: io_uring_setup spuriously returning ENOMEM for one user

[Andres Freund <andres@anarazel.de>]

Hi,

On 2020-07-16 23:12:41 +0300, Pavel Begunkov wrote:
> On 16/07/2020 23:05, Andres Freund wrote:
> > Hi,
> > 
> > While testing the error handling of my uring using postgres branch I
> > just encountered the situation that io_uring_setup() always fails with
> > ENOMEN.
> > 
> > It only does so for the user I did the testing on and not for other
> > users. During the testing a few io_uring using processes were kill -9'd
> > and a few core-dumped after abort(). No io_uring using processes are
> > still alive.
> > 
> > As the issue only happens to the one uid I suspect that
> > current_user()->locked_mem got corrupted, perhaps after hitting the
> > limit for real.
> 
> Any chance it's using SQPOLL mode?

No. It's a "plain" uring. The only thing that could be considered
special is that one of the rings is shared between processes (which all
run as the same user).

Greetings,

Andres Freund