Re: [PATCH] workqueue: rust: add creation of workqueues

[Tejun Heo]

Hello, Alice.

On Wed, Apr 16, 2025 at 09:41:21PM +0200, Alice Ryhl wrote:
...
> I thought about implementation approaches. The first thought that
> sprang to mind is add a list of all delayed work items, but now I
> think we can do better. We can have an atomic counter tracking the
> number of delayed work items, and have destroy_workqueue() do this:
> 
> retry:
> drain_workqueue(wq);
> if (has_delayed_work_items(wq)) {
>     wait_for_delayed_to_be_scheduled(wq);
>     goto retry;
> }
> 
> where wait_for_delayed_to_be_scheduled() either waits for the counter
> to hit zero, or waits for at least waits for one of them to be
> scheduled. For example, maybe wait_for_delayed_to_be_scheduled() could
> add a dummy work item *without* waking up the worker threads, and then
> wait for that work item to get executed, which would effectively mean
> that it sleeps until something else wakes up a worker.

I suppose that can work too but the delays can be pretty long, so while
correct, I'm not sure it'd be very pleasant to use. If we per-cpu lists, I
don't think the overhead would be all that noticeable, so may as well do
that?

Thanks.

-- 
tejun