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

[Stefan Wahren]

Hi Jakub,

Am 26.01.24 um 03:36 schrieb Jakub Kicinski:
> 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.
there is actually another reason for this change which is not mentioned
in the commit message. The pointer spi_thread can have 3 states:
- valid thread
- error pointer
- NULL

So the second motivation was to eliminate the possibility of an error
pointer
by using a local variable. So we only have to care about NULL.

I will change this in V4.
> > @@ -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.
Oops

Best regards
> Rest of the series LGTM!