[openib-general] [PATCH ] RFC IB/cm do not track remote QPN in timewait state
Michael S. Tsirkin
mst at mellanox.co.il
Mon Aug 28 13:47:27 PDT 2006
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
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