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

[Horms <horms@verge.net.au>]

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
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/