Re: [PATCH rdma-rc 06/10] RDMA/mlx5: Fix mkey cache possible deadlock on cleanup

[Leon Romanovsky <leon@kernel.org>]

On Mon, Jun 05, 2023 at 01:54:38PM -0300, Jason Gunthorpe wrote:
> On Mon, Jun 05, 2023 at 01:33:22PM +0300, Leon Romanovsky wrote:
> 
> > diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> > index 1ce48e485c5b..f113656e4027 100644
> > --- a/drivers/infiniband/hw/mlx5/mr.c
> > +++ b/drivers/infiniband/hw/mlx5/mr.c
> > @@ -1033,7 +1033,15 @@ void mlx5_mkey_cache_cleanup(struct mlx5_ib_dev *dev)
> >  		xa_lock_irq(&ent->mkeys);
> >  		ent->disabled = true;
> >  		xa_unlock_irq(&ent->mkeys);
> > -		cancel_delayed_work_sync(&ent->dwork);
> > +	}
> > +
> > +	/* Run the canceling of delayed works on the cache in a separate loop after
> > +	 * disabling all entries to ensure someone_adding() will not try taking the
> > +	 * rb_lock while flushing the workqueue.
> > +	 */
> > +	for (node = rb_first(root); node; node = rb_next(node)) {
> > +		ent = rb_entry(node, struct mlx5_cache_ent, node);
> > +		cancel_delayed_work(&ent->dwork);
> >  	}
> >
> This goes on to kfree end, so this can't drop the sync.

with _sync, we will get same code as it was before.
Let's put this patch aside.

Thanks

> 
> Jason