> Hi Wei,
>
> On Mon, Sep 23, 2024 at 04:59:56AM +0300, Wei Fang wrote:
> > Okay, I have tested this solution (see changes below), and from what I
> observed,
> > the xdp_tx_in_flight can naturally drop to 0 in every test. So if there are no
> other
> > risks, the next version will use this solution.
> >
>
> Sorry for the delay. I have tested this variant and it works. Just one
> thing below.
>
> > @@ -2467,10 +2469,6 @@ void enetc_start(struct net_device *ndev)
> > struct enetc_ndev_priv *priv = netdev_priv(ndev);
> > int i;
> >
> > - enetc_setup_interrupts(priv);
> > -
> > - enetc_enable_tx_bdrs(priv);
> > -
> > for (i = 0; i < priv->bdr_int_num; i++) {
> > int irq = pci_irq_vector(priv->si->pdev,
> >
> ENETC_BDR_INT_BASE_IDX + i);
> > @@ -2479,6 +2477,10 @@ void enetc_start(struct net_device *ndev)
> > enable_irq(irq);
> > }
> >
> > + enetc_setup_interrupts(priv);
> > +
> > + enetc_enable_tx_bdrs(priv);
> > +
> > enetc_enable_rx_bdrs(priv);
> >
> > netif_tx_start_all_queues(ndev);
> > @@ -2547,6 +2549,12 @@ void enetc_stop(struct net_device *ndev)
> >
> > enetc_disable_rx_bdrs(priv);
> >
> > + enetc_wait_bdrs(priv);
> > +
> > + enetc_disable_tx_bdrs(priv);
> > +
> > + enetc_clear_interrupts(priv);
>
> Here, NAPI may still be scheduled. So if you clear interrupts, enetc_poll()
> on another CPU might still have time to re-enable them. This makes the
> call pointless.
>
> Please move the enetc_clear_interrupts() call after the for() loop below
> (AKA leave it where it is).
Okay, I will, thanks.
>
> > +
> > for (i = 0; i < priv->bdr_int_num; i++) {
> > int irq = pci_irq_vector(priv->si->pdev,
> >
> ENETC_BDR_INT_BASE_IDX + i);
> > @@ -2555,12 +2563,6 @@ void enetc_stop(struct net_device *ndev)
> > napi_synchronize(&priv->int_vector[i]->napi);
> > napi_disable(&priv->int_vector[i]->napi);
> > }
> > -
> > - enetc_wait_bdrs(priv);
> > -
> > - enetc_disable_tx_bdrs(priv);
> > -
> > - enetc_clear_interrupts(priv);
> > }
> > EXPORT_SYMBOL_GPL(enetc_stop);
>
> FWIW, there are at least 2 other valid ways of solving this problem. One
> has already been mentioned (reset the counter in enetc_free_rx_ring()):
>
> @@ -2014,6 +2015,8 @@ static void enetc_free_rx_ring(struct enetc_bdr
> *rx_ring)
> __free_page(rx_swbd->page);
> rx_swbd->page = NULL;
> }
> +
> + rx_ring->xdp.xdp_tx_in_flight = 0;
> }
>
> static void enetc_free_rxtx_rings(struct enetc_ndev_priv *priv)
>
> And the other would be to keep rescheduling NAPI until there are no more
> pending XDP_TX frames.
>
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c
> b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 3cff76923ab9..36520f8c49a6 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -1689,6 +1689,7 @@ static int enetc_poll(struct napi_struct *napi, int
> budget)
> work_done = enetc_clean_rx_ring_xdp(rx_ring, napi, budget, prog);
> else
> work_done = enetc_clean_rx_ring(rx_ring, napi, budget);
> - if (work_done == budget)
> + if (work_done == budget || rx_ring->xdp.xdp_tx_in_flight)
> complete = false;
> if (work_done)
>
> But I like your second proposal the best. It doesn't involve adding an
> unnecessary extra test in the fast path.
