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SubjectRe: [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit()
On Thu, 12 Aug 2021 14:50:33 -0500 Alex Elder wrote:
> + /* The hardware must be powered for us to transmit */
> + dev = &ipa->pdev->dev;
> + ret = pm_runtime_get(dev);
> + if (ret < 1) {
> + /* If a resume won't happen, just drop the packet */
> + if (ret < 0 && ret != -EINPROGRESS) {
> + pm_runtime_put_noidle(dev);
> + goto err_drop_skb;
> + }

This is racy, what if the pm work gets scheduled on another CPU and
calls wake right here (i.e. before you call netif_stop_queue())?
The queue may never get woken up?

> + /* No power (yet). Stop the network stack from transmitting
> + * until we're resumed; ipa_modem_resume() arranges for the
> + * TX queue to be started again.
> + */
> + netif_stop_queue(netdev);
> +
> + (void)pm_runtime_put(dev);
> +
> + return NETDEV_TX_BUSY;

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