Re: [PATCH for-next v11 08/11] RDMA/rxe: Add code to cleanup mcast memory

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Feb 11, 2022 at 06:37:50PM -0600, Bob Pearson wrote:
> > The mcast attachment is affiliated with a QP, when all the QPs are
> > destroyed, which are rdma-core objects, then all attachments should be
> > free'd as well. That should have happened by the time things get here
> > 
> > I would expect a simple WARN_ON that the rb tree is empty in destroy
> > to catch any bugs.
> > 
> > Jason
>
> I wrote a simple user test case that calls ibv_attach_mcast() and
> then sleeps.  If I type ^C the qp is detached as you predicted so
> someone is counting them somewhere. It isn't obvious in rdma-core.

QP destroy is done inside the kernel in all the uverbs stuff, detatch
from multicast during QP destroy should have been inside RXE's qp
destroy function.

> never get called since someone above me is actively cleaning them up
> from failed apps. Or we can just drop this patch and assume it isn't
> needed.

I mean drop this patch and just put a WARN_ON to assert the rb tree is
empty before destroying the memory that holds it, just in case someone
adds a bug someday.

Jason