Re: [PATCH v7 10/30] net: wan: Add support for QMC HDLC

[Herve Codina]

Hi Jakub,

On Fri, 6 Oct 2023 14:47:02 -0700
Jakub Kicinski <k...@kernel.org> wrote:

> On Thu, 28 Sep 2023 09:06:28 +0200 Herve Codina wrote:
> > +static int qmc_hdlc_close(struct net_device *netdev)
> > +{
> > +   struct qmc_hdlc *qmc_hdlc = netdev_to_qmc_hdlc(netdev);
> > +   struct qmc_hdlc_desc *desc;
> > +   int i;
> > +
> > +   netif_stop_queue(netdev);
> > +
> > +   qmc_chan_stop(qmc_hdlc->qmc_chan, QMC_CHAN_ALL);
> > +   qmc_chan_reset(qmc_hdlc->qmc_chan, QMC_CHAN_ALL);  
> 
> stopping the queue looks a bit racy, a completion may come in 
> and restart the queue

Indeed, qmc_hdlc_xmit_complete() completion can restart the queue.

I will call netif_stop_queue() after calling qmc_chan_stop/reset().
This is the simple way to fix that without adding an internal flag.

Thanks for pointing that.

Best regards,
Hervé

> 
> > +   for (i = 0; i < ARRAY_SIZE(qmc_hdlc->tx_descs); i++) {
> > +           desc = &qmc_hdlc->tx_descs[i];
> > +           if (!desc->skb)
> > +                   continue;
> > +           dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size,
> > +                            DMA_TO_DEVICE);
> > +           kfree_skb(desc->skb);
> > +           desc->skb = NULL;
> > +   }
> > +
> > +   for (i = 0; i < ARRAY_SIZE(qmc_hdlc->rx_descs); i++) {
> > +           desc = &qmc_hdlc->rx_descs[i];
> > +           if (!desc->skb)
> > +                   continue;
> > +           dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size,
> > +                            DMA_FROM_DEVICE);
> > +           kfree_skb(desc->skb);
> > +           desc->skb = NULL;
> > +   }
> > +
> > +   hdlc_close(netdev);