Re: [PATCH 3/6] workqueue: make cancel_rearming_delayed_workqueue() work on idle dwork

Oleg Nesterov
2007-02-07T17:41:40Z

On 02/07, Oleg Nesterov wrote:
>
> The following code
>
> schedule_delayed_work(dw);
> cancel_rearming_delayed_workqueue(dw); // OK
> cancel_rearming_delayed_workqueue(dw); // HANGS!
>
> still doesn't work.

I think we have another problem with delayed_works.

cancel_rearming_delayed_workqueue() doesn't garantee that the ->func() is not
running upon return. I don't know if it is bug or not, the comment says nothing
about that.

However, we have the callers which seem to assume the opposite, example

net/ipv4/ipvs/ip_vs_core.c

module_exit
ip_vs_cleanup
ip_vs_control_cleanup
cancel_rearming_delayed_work
// done

This is unsafe. The module may be unloaded and the memory may be freed
while defense_work_handler() is still running/preempted.

Unless I missed something, which side should be fixed?

Oleg.