[openib-general] [PATCH] for 2-6-19 rdma/addr: use client registration to fix module unload race

[Michael S. Tsirkin]

Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
> Subject: Re: [PATCH] for 2-6-19 rdma/addr: use client registration to fix module unload race
> 
> > All active side users are fine I think.  But any client on the passive side
> > currently might destroy the new ID by returning error from the callback, and I
> > like this interface since it frees the resources immediately.
> 
> As long as only *newly* created (i.e. associated with a connection request) 
> cm_id's are destroyed this way, we're fine.  Newly created cm_id's are 
> associated with a listening cm_id.  Destruction of the listening cm_id is 
> blocked while a callback for a connection request is in progress.
> 
> > Since all such passive side users currently are out of tree, I don't think
> > it's urgent for us to do anything about the passive side race - but please do
> > not at least break code that uses passive side in major ways just yet.
> 
> I use the callback method of destruction for new cm_id's in the ucm and ucma
> modules, so I want to keep this feature myself.  However, this method is
> unused, and likely unneeded, for events other than connection requests.  If
> this is the case, we can update the documentation, and remove this support
> except for new connections.

Another case is a request and then a reject.

> I looked at the existing users and didn't find any module unload races with 
> either the ib_cm or rdma_cm, so I don't think that any immediate fixes are 
> necessary.
> 
> - Sean
> 

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MST