On 12/7/22 2:18 PM, Pavel Begunkov wrote:
> On 12/7/22 15:51, Jens Axboe wrote:
>> On 12/7/22 8:31 AM, Jens Axboe wrote:
>>> On 12/6/22 8:53?PM, Pavel Begunkov wrote:
>>>> @@ -43,6 +61,15 @@ static int io_msg_ring_data(struct io_kiocb *req)
>>>> if (msg->src_fd || msg->dst_fd || msg->flags)
>>>> return -EINVAL;
>>>> + if (target_ctx->task_complete && current != target_ctx->submitter_task) {
>>>> + init_task_work(&msg->tw, io_msg_tw_complete);
>>>> + if (task_work_add(target_ctx->submitter_task, &msg->tw,
>>>> + TWA_SIGNAL))
>>>> + return -EOWNERDEAD;
>>>> +
>>>> + return IOU_ISSUE_SKIP_COMPLETE;
>>>> + }
>>>> +
>>>
>>> We should probably be able to get by with TWA_SIGNAL_NO_IPI here, no?
>>
>> Considering we didn't even wake before, I'd say that's a solid yes.
>
> I'm not so sure. It'll work, but a naive approach would also lack
> IORING_SETUP_TASKRUN_FLAG and so mess with latencies when it's not
> desirable.
>
> option 1)
>
> method = TWA_SIGNAL;
> if (flags & IORING_SETUP_TASKRUN_FLAG)
> method = NO_IPI;
>
> option 2)
>
> task_work_add(NO_IPI);
> atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
>
>
> Might be better to have one of those.
I like option 2, which should be fine.
--
Jens Axboe
