Re: io_uring_setup spuriously returning ENOMEM for one user

[Jens Axboe <axboe@kernel.dk>]

On 7/16/20 2:20 PM, Andres Freund wrote:
> 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).

Do you have this one:

ommit 309fc03a3284af62eb6082fb60327045a1dabf57 (tag: io_uring-5.8-2020-07-10)
Author: Jens Axboe <axboe@kernel.dk>
Date:   Fri Jul 10 09:13:34 2020 -0600

    io_uring: account user memory freed when exit has been queued

-- 
Jens Axboe