Re: [PATCH] kthread: add kthread_mod_pending_delayed_work api

[Yiwei Zhang‎]

> 2. User triggered clean up races with the clean up triggered by
>   timeout. You try to handle this scenario by this patch.
Yes, exactly.

> 3. User does clean up after the clean up has already been done
>   by the timeout.
This case is well handled. So only (2) has a potential race.

Let me clarify a bit more here. The "clean up" is not the clean up
when a process tears down, but it's actually a "post-work" to cancel
out an early "pre-work". The "pre-work" enqueues the delayed "post
work" for the timeout purpose. That pair of operations can repeatedly
happen.

The racing is currently worked around by refcounting the delayed_work
container, and the later "post-work" will take care of the work
deallocation.

I mainly want to reach out to see if we agree that this is a valid API
to be supported by kthread. Or we extend the existing
kthread_mod_delayed_work api to take another option to not re-queue if
the cancel failed.

Best,
Yiwei