Re: [rdma-next 01/33] Revert "IB/core: Add flow control to the portmapper netlink calls"

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Aug 01, 2017 at 10:15:11AM -0500, Chien Tin Tung wrote:
> On Tue, Aug 01, 2017 at 09:22:47AM -0500, Christopher Lameter wrote:
> > On Tue, 1 Aug 2017, Chien Tin Tung wrote:
> > 
> > > Why do I need to explain the original patch?  It was accepted many kernels
> > > ago.  Your questions on the original were based on false assumptions and
> > > facts which I've proven over and over.  You are right in that I do
> > > not want to revisit those either.  There is a patch that can solve
> > > the problem you are facing but yet you insist on the revert.  This is
> > > very puzzling to me.  You simply refuse to move this forward.  That
> > > is your choice but revert is a no go for me.
> > 
> > Ok this is pretty confusing to someone not involved in the prior
> > discussions. Could both of your stop attacking each other and start
> > talking about the technical issues?
> 
> There's been multiple threads over this revert.  This one is the
> latest Leon walked away from: https://patchwork.kernel.org/patch/9814367/
> 
> I'm simply asking for proof/evidence/facts to back up Leon's claims.
> Show me the code/stack trace/whatever and I will be happy to admit wrong
> publicly on the list and move on.  I do have better things to do than
> to NACK a revert.

Well, I think the design of the netlink protocol in iwpmd is pretty
strange, but audit netlink is the other major user of blocking
netlink_uncast to achive some reliability, so it should be workable
here as well.

Presumably the iwpmd kernel side is designed to handle the locking
right to avoid deadlocks.

I'm not sure why there is so much noise about this - yes, iwpmd is
really weird, but it is a UAPI, we can't change it and we can't demand
they change. For better or worse the protocol is based on
'near-reliable' netlink delivery of messages and we are stuck with
that.

Leon is also right that every other user of netlink_unicast in rdma
should be using the non-blocking version.

So, the above patch seems like a sensible approach to me..

Jason
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