Subject: Re: [PATCH V3 01/14 next] qca_spi: Improve SPI thread creation

From: Jakub Kicinski <[email-masked]>
Date: Thu, 25 Jan 2024 18:36:39 -0800

On Wed, 24 Jan 2024 23:31:58 +0100 Stefan Wahren wrote:
> The qca_spi driver create/stop the SPI kernel thread in case
> of netdev_open/close. This isn't optimal because there is no
> need for such an expensive operation.
> 
> So improve this by moving create/stop of the SPI kernel into
> the init/uninit ops. The open/close ops could just
> 'park/unpark' the SPI kernel thread.

What's the concern? I don't think that creating a thread is all
expensive. And we shouldn't have a thread sitting around when
the interface isn't use. I mean - if you ask me what's better
a small chance that the creation will fail at open or having
a parked and unused thread when device is down - I'd pick
the former.. But I may well be missing the point.

> @@ -825,6 +813,7 @@ static int
>  qcaspi_netdev_init(struct net_device *dev)
>  {
>  	struct qcaspi *qca = netdev_priv(dev);
> +	struct task_struct *thread;
> 
>  	dev->mtu = QCAFRM_MAX_MTU;
>  	dev->type = ARPHRD_ETHER;
> @@ -848,6 +837,15 @@ qcaspi_netdev_init(struct net_device *dev)
>  		return -ENOBUFS;
>  	}
> 
> +	thread = kthread_create(qcaspi_spi_thread, qca, "%s", dev->name);
> +	if (IS_ERR(thread)) {
> +		netdev_err(dev, "%s: unable to start kernel thread.\n",
> +			   QCASPI_DRV_NAME);
> +		return PTR_ERR(thread);

I'm 90% sure this leaks resources on failure, too.

Rest of the series LGTM!