On Wed, Jun 15, 2022 at 08:29:31PM -0500, Frank Zago wrote:
> On 5/23/22 11:16, Johan Hovold wrote:
> >> +static void ch341_gpio_irq_enable(struct irq_data *data)
> >> +{
> >> + struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> >> + int rc;
> >> +
> >> + /*
> >> + * The URB might have just been unlinked in
> >> + * ch341_gpio_irq_disable, but the completion handler hasn't
> >> + * been called yet.
> >> + */
> >> + if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
> >> + usb_kill_anchored_urbs(&dev->irq_urb_out);
> >> +
> >> + usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
> >> + rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
> >> + if (rc)
> >> + usb_unanchor_urb(dev->irq_urb);
> >
> > This looks confused and broken.
> >
> > usb_kill_anchored_urbs() can sleep so either calling it is broken or
> > using GFP_ATOMIC is unnecessary.
>
> Right, that function can sleep. I changed GFP_ATOMIC to GFP_KERNEL.
These callbacks can be called in atomic context so that's not an option,
I'm afraid.
> > And isn't this function called multiple times when enabling more than
> > one irq?!
>
> There's only one IRQ, so only one URB will be posted at a time. It
> is reposted as soon as it comes back unless the IRQ is disabled or
> the device stops.
AFAICT you have up to 16 (CH341_GPIO_NUM_PINS) interrupts, not one. So I
still say this is broken.
> >> +}
> >> +
> >> +static void ch341_gpio_irq_disable(struct irq_data *data)
> >> +{
> >> + struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> >> +
> >> + usb_unlink_urb(dev->irq_urb);
> >
> > Same here...
> >> +}
> >> +
> >> +static int ch341_gpio_remove(struct platform_device *pdev)
> >> +{
> >> + struct ch341_gpio *dev = platform_get_drvdata(pdev);
> >> +
> >> + usb_kill_anchored_urbs(&dev->irq_urb_out);
> >
> > You only have one URB...
> >
> > And what prevents it from being resubmitted here?
>
> I don't see what would resubmit it here. The gpio is being released.
Your implementation needs to handle racing requests. The gpio chip is
still registered here.
Johan
