Re: bug with fastpoll accept and sqpoll + IOSQE_FIXED_FILE

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

On 02/02/2021 11:05, Pavel Begunkov wrote:
> On 02/02/2021 05:36, Victor Stewart wrote:
>> started experimenting with sqpoll and my fastpoll accepts started
>> failing. was banging my head against the wall for a few hours... wrote
>> this test case below....
>>
>> basically fastpoll accept only works without sqpoll, and without
>> adding IOSQE_FIXED_FILE to the sqe. fails with both, fails with
>> either. these must be bugs?
>>
>> I'm running Clear Linux 5.10.10-1017.native.
>>
>> i hope no one here is allergic to C++, haha. compilation command
>> commented in the gist, just replace the two paths. and I can fold
>> these checks if needed into a liburing PR later.
>>
>> https://gist.github.com/victorstewart/98814b65ed702c33480487c05b40eb56
> 
> Please don't forget about checking error codes. At least fixed
> files don't work for you because of
> 
> int fds[10];
> memset(fds, -1, 10); // 10 bytes, not 10 ints
> 
> So io_uring_register_files() silently fails.
> 
> 
> For me, all two "with SQPOLL" tests spit SUCCESS, then it hangs.
> But need to test it with upstream to be sure.

Also you forget to submit, all works with these 2 changes.

When you don't do io_uring_submit(), apparently it gets live-locked
in liburing's _io_uring_get_cqe(), that's a bug.

-- 
Pavel Begunkov