Re: [PATCH 1/1] Revert "RDMA/rxe: Add workqueue support for rxe tasks"

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Oct 10, 2023 at 04:53:55AM +0000, Daisuke Matsuda (Fujitsu) wrote:

> Solution 1: Reverting "RDMA/rxe: Add workqueue support for rxe tasks"
> I see this is supported by Zhu, Bart and approved by Leon.
> 
> Solution 2: Serializing execution of work items
> > -       rxe_wq = alloc_workqueue("rxe_wq", WQ_UNBOUND, WQ_MAX_ACTIVE);
> > +       rxe_wq = alloc_workqueue("rxe_wq", WQ_HIGHPRI | WQ_UNBOUND, 1);
> 
> Solution 3: Merging requester and completer (not yet submitted/tested)
> https://lore.kernel.org/all/93c8ad67-f008-4352-8887-099723c2f4ec@gmail.com/
> Not clear to me if we should call this a new feature or a fix.
> If it can eliminate the hang issue, it could be an ultimate solution.
> 
> It is understandable some people do not want to wait for solution 3 to be submitted and verified.
> Is there any problem if we adopt solution 2?
> If so, then I agree to going with solution 1.
> If not, solution 2 is better to me.

I also do not want to go backwards, I don't believe the locking is
magically correct under tasklets. 2 is painful enough to continue to
motivate people to fix this while unbreaking block tests.

I'm still puzzled why Bob can't reproduce the things Bart has seen.

Jason