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

Horms
2007-02-08T03:09:01Z

On Wed, Feb 07, 2007 at 08:43:55PM +0300, Oleg Nesterov wrote:
> 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?

Assuming the decision is to fix the ipvs side, is the fix
just to remove the call to cancel_rearming_delayed_work() in
ip_vs_control_cleanup() ?

--
Horms
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