On Sun, Oct 05, 2025 at 02:56:05PM -0600, Jens Axboe wrote:
> 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

I tried reproducing it in a smaller file. Assume I did everything wrong but somehow I seem to get results and they're not correct.

The codebase I'd like to use this in has very little activity (could go seconds without a single syscall), then execute a few hundreds-thousand (which I like to be async).
SQPOLL sounds like the one best for my usecase. You can see I updated the sq tail before enter and I used IORING_ENTER_SQ_WAKEUP + slept for a second.
The sq tail isn't zero which means I have results? and you can see its 10 of the same user_data

cq head is 0 enter result was 10
1234 0
1234 0
1234 0
1234 0
1234 0
1234 0
1234 0
1234 0
1234 0
1234 0
FFFFFFFF -1