[openib-general] [PATCH ] RFC IB/cm do not track remote QPN in timewait state

[Michael S. Tsirkin]

Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
> Subject: Re: [PATCH ] RFC IB/cm do not track remote QPN in timewait state
> 
> Michael S. Tsirkin wrote:
> >>The CM tracks the remote QP, not the local.
> > 
> > 
> > I might not have been clear.
> > For connection in timewait state, spec explicitly says local QP
> > must be in reset, error or init.
> > Only after it goes out of timewait can you destroy the QP.
> > That's the tracking I think spec means CM needs to do.
> 
> I believe that this tracking is done, and is reported to the user by the 
> timewait exit event.  QP transitions are the responsibility of the user.
> 
> This is related to a problem that Arlin and I have been discussing.  There's 
> nothing that the CM does to prevent the QP from being destroyed, especially for 
> a usermode application.  The CM invokes a callback once a connection exits 
> timewait, indicating to the user that the QP may now be destroyed.  But if an 
> application crashes, uverbs automatically destroys the QP.
> 
> We may need better coordination between the CM and verbs wrt timewait to handle 
> userspace QPs, but this depends on this change.

Another problem that  I see is that CMA currently seems to completely 
mask timewait exit.

So there's no way to properly handle timewait on top of cma that I can see.



-- 
MST