Re: Submitting IO events with IORING_FEAT_NODROP and overflown CQ ring

[Jens Axboe <axboe@kernel.dk>]

On 5/3/24 5:21 PM, Alexander Babayants wrote:
> Hi!
> 
> Per io_uring_setup(2):
> 
>> IORING_FEAT_NODROP
> ...
>> If this overflow condition is entered,
>> attempting to submit more IO will fail with the -EBUSY
>> error value, if it can't flush the overflown events to the
>> CQ ring. If this happens, the application must reap events
>> from the CQ ring and attempt the submit again.
> 
> But I'm not getting -EBUSY on a 6.2 kernel when submitting to the ring
> with a full CQ ring and an overflow flag set. I'm not an expert in
> uring code, but it seems the error was removed in commit
> 1b346e4aa8e79227391ffd6b7c6ee5acf0fa8bfc. Could you please check if
> I'm right and if that change was intentional?

This is correct and intentional. The man page should get updated with a
note on the current behavior.

-- 
Jens Axboe