On 3/9/22 9:03 PM, Jens Axboe wrote: > I'll mull over this a bit... One idea... You issue the request as you normally would for ring1, and you mark that request A with IOSQE_CQE_SKIP_SUCCESS. Then you link an IORING_OP_WAKEUP_RING to request A, with the fd for it set to ring2, and also mark that with IOSQE_CQE_SKIP_SUCCESS. We'd need to have sqe->addr (or whatever field) in the WAKEUP_RING request be set to the user_data of request A, so we can propagate it. The end result is that ring1 won't see any completions for request A or the linked WAKEUP, unless one of them fails. If that happens, then you get to process things locally still, but given that this is a weird error case, shouldn't affect things in practice. ring2 will get the CQE posted once request A has completed, with the user_data filled in from request A. Which is really what we care about here, as far as I understand. This basically works right now with what I posted, and without needing to rearchitect a bunch of stuff. And it's pretty efficient. Only thing we'd need to add is passing in the target cqe user_data for the WAKEUP request. Would just need to be wrapped in something that allows you to do this easily, as it would be useful for others too potentially. -- Jens Axboe
