On 8/30/22 15:23, Dylan Yudaken wrote:
On Mon, 2022-08-29 at 14:32 +0800, Hao Xu wrote:
@@ -3289,17 +3409,29 @@ static __cold int
io_uring_create(unsigned
entries, struct io_uring_params *p,
if (ctx->flags & IORING_SETUP_SQPOLL) {
/* IPI related flags don't make sense with SQPOLL */
if (ctx->flags & (IORING_SETUP_COOP_TASKRUN |
- IORING_SETUP_TASKRUN_FLAG))
+ IORING_SETUP_TASKRUN_FLAG |
+ IORING_SETUP_DEFER_TASKRUN))
Sounds like we should also fail if SQPOLL is set, especially with
the task check on the waiting side.
sqpoll as a natural single issuer case, shouldn't we support this
feature for it? And surely, in that case, don't do local task work
check
in cqring wait time and be careful in other places like
io_uring_register
I think there is definitely scope for that - but it's less obvious how
to do it.
i.e. in it's current form DEFER_TASKRUN requires the GETEVENTS to be
submitted on the same task as the initial submission, but with SQPOLL
the submission task is a kernel thread so would have to have some
difference in the API.
Yea, just like what I said, in sqpoll mode, we shouldn't do the tw
handle in the io_uring_enter.
As an idea for a later patch set - perhaps the semantics should be to
keep task work local but only run it once submissions have been
processed for a ctx. I suspect that will require some care to ensure
the wakeup flag is set correctly and that it cleans up properly.
Yea, it should be a separate follow-up patchset, currently there is a
io_run_task_work() after submitted sqes for all ctxes and before going
to sleep, that may be a good place for it. I haven't think about it in
detail, but there should be a viable way.
Dylan
