[openib-general] Re: netdev reference counting problem with ib_at

[Hal Rosenstock]

On Fri, 2005-09-30 at 14:28, Pradeep Satyanarayana wrote:
> I have been following this and the other thread on CMA. There appears
> to be some opinions to removing the ib_at module and introduce CMA.
> Is that correct? 
> 
> True, CMA will need some form of address translation. Can we not use
> some incarnation of ib_at for that? I realize that ib_at has a
> net_device
> refcnt problem. Is this refcnt problem a usage issue rather than just
> a bug in the implementation? 

It's an implementation issue which can be fixed. The address translation
portion of CMA will need to do something similar (as SDP does or a fixed
AT would).

-- Hal

> How would CMA solve the refcnt issue?
> What am I missing?
> 
> Pradeep
> pradeep at us.ibm.com
> 
> 
> openib-general-bounces at openib.org wrote on 09/30/2005 07:27:32 AM:
> 
> > On Tue, 2005-09-27 at 00:08, Michael S. Tsirkin wrote:
> > > Why does AT need to keep netdev reference for longer?
> > 
> > I don't think it really does and could be changed. I think (but am
> not
> > sure) it was a convenience of implementation to try to make the
> netdev
> > reference counting simpler.
> > 
> > It only needs to hold the netdev for sending the ARP (like SDP).
> > 
> > It needs the underlying ib_device and port for ATS and path queries
> as
> > well as reregistration if the interface address changes and
> > deregistration if the IPoIB interface is removed. (SDP doesn't need
> to
> > worry about these aspects (only path queries).)
> > 
> > -- Hal
> > 
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