On Wed, Jun 12, 2019 at 12:01:23PM +0000, Mark Zhang wrote:
> On 6/12/2019 1:54 AM, Jason Gunthorpe wrote:
> > On Thu, Jun 06, 2019 at 01:53:37PM +0300, Leon Romanovsky wrote:
> >> From: Mark Zhang <markz@xxxxxxxxxxxx>
> >>
> >> Add support for ib callbacks counter_bind_qp() and counter_unbind_qp().
> >>
> >> Signed-off-by: Mark Zhang <markz@xxxxxxxxxxxx>
> >> Reviewed-by: Majd Dibbiny <majd@xxxxxxxxxxxx>
> >> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> >> drivers/infiniband/hw/mlx5/main.c | 53 +++++++++++++++++++++++++++++++
> >> 1 file changed, 53 insertions(+)
> >>
> >> diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
> >> index 8b7bcf8f68fb..66c94a060718 100644
> >> +++ b/drivers/infiniband/hw/mlx5/main.c
> >> @@ -5533,6 +5533,57 @@ static int mlx5_ib_get_hw_stats(struct ib_device *ibdev,
> >> return num_counters;
> >> }
> >>
> >> +static int mlx5_ib_counter_bind_qp(struct rdma_counter *counter,
> >> + struct ib_qp *qp)
> >> +{
> >> + struct mlx5_ib_dev *dev = to_mdev(qp->device);
> >> + u16 cnt_set_id = 0;
> >> + int err;
> >> +
> >> + if (!counter->id) {
> >> + err = mlx5_cmd_alloc_q_counter(dev->mdev,
> >> + &cnt_set_id,
> >> + MLX5_SHARED_RESOURCE_UID);
> >> + if (err)
> >> + return err;
> >> + counter->id = cnt_set_id;
> >> + }
> >> +
> >> + err = mlx5_ib_qp_set_counter(qp, counter);
> >> + if (err)
> >> + goto fail_set_counter;
> >> +
> >> + return 0;
> >> +
> >> +fail_set_counter:
> >> + mlx5_core_dealloc_q_counter(dev->mdev, cnt_set_id);
> >> + counter->id = 0;
> >> +
> >> + return err;
> >> +}
> >> +
> >> +static int mlx5_ib_counter_unbind_qp(struct ib_qp *qp, bool force)
> >> +{
> >> + struct mlx5_ib_dev *dev = to_mdev(qp->device);
> >> + struct rdma_counter *counter = qp->counter;
> >> + int err;
> >> +
> >> + err = mlx5_ib_qp_set_counter(qp, NULL);
> >> + if (err && !force)
> >> + return err;
> >> +
> >> + /*
> >> + * Deallocate the counter if this is the last QP bound on it;
> >> + * If @force is set then we still deallocate the q counter
> >> + * no matter if there's any error in previous. used for cases
> >> + * like qp destroy.
> >> + */
> >> + if (atomic_read(&counter->usecnt) == 1)
> >> + return mlx5_core_dealloc_q_counter(dev->mdev, counter->id);
> >
> > This looks like a nonsense thing to write, what it is trying to do
> > with that atomic?
> >
> > I still can't see why this isn't a normal kref.
> >
>
> Hi Jason,
>
> Have discussed with Leon, unlike other resources, counter alloc/dealloc
> isn't called explicitly. So we need a refcount to record how many QPs
> are bound on this counter, when it comes to 0 then the counter can be
> deallocated. Whether to use atomic or kref the code is similar, it is
> not able to take advantage of kref/completion.
That doesn't explain the nonsense "atomic_read(&counter->usecnt) == 1"
test
Jason
