Re: [PATCH for-next 5/7] io_uring: post msg_ring CQE in task context

[Jens Axboe <axboe@kernel.dk>]

On 12/4/22 7:44?PM, Pavel Begunkov wrote:
> We want to limit post_aux_cqe() to the task context when ->task_complete
> is set, and so we can't just deliver a IORING_OP_MSG_RING CQE to another
> thread. Instead of trying to invent a new delayed CQE posting mechanism
> push them into the overflow list.

This is really the only one out of the series that I'm not a big fan of.
If we always rely on overflow for msg_ring, then that basically removes
it from being usable in a higher performance setting.

The natural way to do this would be to post the cqe via task_work for
the target, ring, but we also don't any storage available for that.
Might still be better to alloc something ala

struct tw_cqe_post {
	struct task_work work;
	s32 res;
	u32 flags;
	u64 user_data;
}

and post it with that?

-- 
Jens Axboe