Re: [PATCH v3 10/14] RDMA/ionic: Register device ops for control path

Jason Gunthorpe
2025-07-02T13:18:05Z

On Tue, Jul 01, 2025 at 01:38:44PM +0300, Leon Romanovsky wrote:
> > +static void ionic_flush_qs(struct ionic_ibdev *dev)
> > +{
> > + struct ionic_qp *qp, *qp_tmp;
> > + struct ionic_cq *cq, *cq_tmp;
> > + LIST_HEAD(flush_list);
> > + unsigned long index;
> > +
> > + /* Flush qp send and recv */
> > + rcu_read_lock();
> > + xa_for_each(&dev->qp_tbl, index, qp) {
> > + kref_get(&qp->qp_kref);
> > + list_add_tail(&qp->ibkill_flush_ent, &flush_list);
> > + }
> > + rcu_read_unlock();
>
> Same question as for CQ. What does RCU lock protect here?

It should protect the kref_get against free of qp. The qp memory must
be RCU freed.

But this pattern requires kref_get_unless_zero()

Jason