Re: [PATCH liburing] Fix hang in in io_uring_get_cqe() with iopoll

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

On 21/06/2020 18:23, Jens Axboe wrote:
> On 6/21/20 4:30 AM, Pavel Begunkov wrote:
>> Because of need_resched() check, io_uring_enter() -> io_iopoll_check()
>> can return 0 even if @min_complete wasn't satisfied. If that's the
>> case, __io_uring_get_cqe() sets submit=0 and wait_nr=0, disabling
>> setting IORING_ENTER_GETEVENTS as well. So, it goes crazy calling
>> io_uring_enter() in a loop, not actually submitting nor polling.
>>
>> Set @wait_nr based on actual number of CQEs ready.
>> BTW, atomic_load_acquire() in io_uring_cq_ready() can be replaced
>> with a relaxed one for this particular place.
> 
> Can you preface this with an addition of __io_uring_cqe_ready() that
> doesn't include the load acquire?

Sure

> Also, s/io_adjut_wait_nr/io_adjust_wait_nr for the patch.
Ouch, a typo


-- 
Pavel Begunkov