[openib-general] What context can CM be called from?

[Libor Michalek]

On Tue, Mar 29, 2005 at 09:29:35AM -0800, Sean Hefty wrote:
> Roland Dreier wrote:
> >     Tziporet> Hi, If I remember correctly the verbs of create &
> >     Tziporet> destroy AVs should be enabled from interrupt context too
> >     Tziporet> since they are not privileged verbs. In VAPI we
> >     Tziporet> implemented these verbs in this way and I think it is
> >     Tziporet> important to keep it this way.
> > 
> > Yes, you're correct that the AV verbs are not privileged according to
> > the table in chapter 11 of the IB spec.  I'm not sure that this
> > requires that they must be available from interrupt context but it is
> > reasonable for us to choose the policy that all non-privileged verbs
> > may be called from interrupt context.
> > 
> > Fixing mthca to allow the AH verbs to be callable from interrupt
> > context is easy -- the trivial patch is included below.
> > 
> > I'm not sure if this removes all obstructions to the CM being usable
> > from interrupt context.
> 
> With this patch, changing the kmalloc in cm_alloc_msg() to use 
> GFP_ATOMIC rather than GFP_KERNEL should allow the CM to be usable from 
> interrupt context.  Of course, I haven't actually tested this...
> 
> I have no objection to this change however.

  I could go either way on this issue myself. If the call can only be
made from thread context I will use schedule_work() to execute the 
request to send the dreq. However, I would imagine that other CM users
would want to send requests in interrupt context...

-Libor