Re: CQE repeats the first item?

[Jens Axboe <axboe@kernel.dk>]

On 10/5/25 2:21 PM, Jacob Thompson wrote:
> I'm doing something wrong and I wanted to know if anyone knows what I
> did wrong from the description I'm using syscalls to call
> io_uring_setup and io_uring_enter. I managed to submit 1 item without
> an issue but any more gets me the first item over and over again. In
> my test I did a memset -1 on cqes and sqes, I memset 0 the first ten
> sqes with different user_data (0x1234 + i), and I used the opcode
> IORING_OP_NOP. I called "io_uring_enter(fd, 10, 0,
> IORING_ENTER_SQ_WAKEUP, 0)" and looked at the cq. Item 11 has the
> user_data as '18446744073709551615' which is correct, but the first 10
> all has user_data be 0x1234 which is weird AF since only one item has
> that user_data and I submited 10 I considered maybe the debugger was
> giving me incorrect values so I tried printing the user data in a
> loop, I have no idea why the first one repeats 10 times. I only called
> enter once
> 
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 4660
> Id is 18446744073709551615

You're presumably not updating your side of the CQ ring correctly, see
what liburing does when you call io_uring_cqe_seen(). If that's not it,
then you're probably mishandling something else and an example would be
useful as otherwise I'd just be guessing. There's really not much to go
from in this report.

-- 
Jens Axboe