Re: bug with fastpoll accept and sqpoll + IOSQE_FIXED_FILE

[Pavel Begunkov <asml.silence@gmail.com>]

On 02/02/2021 20:48, Jens Axboe wrote:
> On 2/2/21 1:34 PM, Pavel Begunkov wrote:
>> On 02/02/2021 17:41, Pavel Begunkov wrote:
>>> On 02/02/2021 17:24, Jens Axboe wrote:
>>>> On 2/2/21 10:10 AM, Victor Stewart wrote:
>>>>>> Can you send the updated test app?
>>>>>
>>>>> https://gist.github.com/victorstewart/98814b65ed702c33480487c05b40eb56
>>>>>
>>>>> same link i just updated the same gist
>>>>
>>>> And how are you running it?
>>>
>>> with SQPOLL    with    FIXED FLAG -> FAILURE: failed with error = ???
>>> 	-> io_uring_wait_cqe_timeout() strangely returns -1, (-EPERM??)
>>
>> Ok, _io_uring_get_cqe() is just screwed twice
>>
>> TL;DR
>> we enter into it with submit=0, do an iteration, which decrements it,
>> then a second iteration passes submit=-1, which is returned back by
>> the kernel as a result and propagated back from liburing...
> 
> Yep, that's what I came up with too. We really just need a clear way
> of knowing when to break out, and when to keep going. Eg if we've
> done a loop and don't end up calling the system call, then there's
> no point in continuing.

We can bodge something up (and forget about it), and do much cleaner
for IORING_FEAT_EXT_ARG, because we don't have LIBURING_UDATA_TIMEOUT
reqs for it and so can remove peek and so on.

-- 
Pavel Begunkov