On Sun, Sep 18, 2016 at 10:07:18 -0700, Leon Romanovsky wrote:
> On Thu, Sep 15, 2016 at 10:36:12AM +0300, Yuval Shaia wrote:
> > Hi Adit,
> > Please see my comments inline.
> >
> > Besides that I have no more comment for this patch.
> >
> > Reviewed-by: Yuval Shaia <yuval.sh...@oracle.com>
> >
> > Yuval
> >
> > On Thu, Sep 15, 2016 at 12:07:29AM +0000, Adit Ranadive wrote:
> > > On Wed, Sep 14, 2016 at 05:43:37 -0700, Yuval Shaia wrote:
> > > > On Sun, Sep 11, 2016 at 09:49:19PM -0700, Adit Ranadive wrote:
> > > > > +
> > > > > +static int pvrdma_poll_one(struct pvrdma_cq *cq, struct pvrdma_qp
> > > > **cur_qp,
> > > > > + struct ib_wc *wc)
> > > > > +{
> > > > > + struct pvrdma_dev *dev = to_vdev(cq->ibcq.device);
> > > > > + int has_data;
> > > > > + unsigned int head;
> > > > > + bool tried = false;
> > > > > + struct pvrdma_cqe *cqe;
> > > > > +
> > > > > +retry:
> > > > > + has_data = pvrdma_idx_ring_has_data(&cq->ring_state->rx,
> > > > > + cq->ibcq.cqe, &head);
> > > > > + if (has_data == 0) {
> > > > > + if (tried)
> > > > > + return -EAGAIN;
> > > > > +
> > > > > + /* Pass down POLL to give physical HCA a chance to
> > > > > poll. */
> > > > > + pvrdma_write_uar_cq(dev, cq->cq_handle |
> > > > PVRDMA_UAR_CQ_POLL);
> > > > > +
> > > > > + tried = true;
> > > > > + goto retry;
> > > > > + } else if (has_data == PVRDMA_INVALID_IDX) {
> > > >
> > > > I didn't went throw the entire life cycle of RX-ring's head and tail
> > > > but you
> > > > need to make sure that PVRDMA_INVALID_IDX error is recoverable one, i.e
> > > > there is probability that in the next call to pvrdma_poll_one it will
> > > > be fine.
> > > > Otherwise it is an endless loop.
> > >
> > > We have never run into this issue internally but I don't think we can
> > > recover here
> >
> > I briefly reviewed the life cycle of RX-ring's head and tail and didn't
> > caught any suspicious place that might corrupt it.
> > So glad to see that you never encountered this case.
> >
> > > in the driver. The only way to recover would be to destroy and recreate
> > > the CQ
> > > which we shouldn't do since it could be used by multiple QPs.
> >
> > Agree.
> > But don't they hit the same problem too?
> >
> > > We don't have a way yet to recover in the device. Once we add that this
> > > check
> > > should go away.
> >
> > To be honest i have no idea how to do that - i was expecting driver's
> > vendors
> > to come up with an ideas :)
> > I once came up with an idea to force restart of the driver but it was
> > rejected.
> >
> > >
> > > The reason I returned an error value from poll_cq in v3 was to break the
> > > possible
> > > loop so that it might give clients a chance to recover. But since poll_cq
> > > is not expected
> > > to fail I just log the device error here. I can revert to that version if
> > > you want to break
> > > the possible loop.
> >
> > Clients (ULPs) cannot recover from this case. They even do not check the
> > reason of the error and treats any error as -EAGAIN.
>
> It is because poll_one is not expected to fall.
Poll_one is an internal function in our driver. ULPs should still be okay I
think as long as poll_cq
does not fail, no?
