On Fri, 20 Nov 2015, Marek Szyprowski wrote:
> From: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx>
>
> Change behavior during registration of gadgets and
> gadget drivers in udc-core. Instead of previous
> approach when for successful probe of usb gadget driver
> at least one usb gadget should be already registered
> use another one where gadget drivers and gadgets
> can be registered in udc-core independently.
>
> Independent registration of gadgets and gadget drivers
> is useful for built-in into kernel gadget and gadget
> driver case - because it's possible that gadget is
> really probed only on late_init stage (due to deferred
> probe) whereas gadget driver's probe is silently failed
> on module_init stage due to no any UDC added.
>
> Also it is useful for modules case - now there is no
> difference what module to insert first: gadget module
> or gadget driver one.
>
> Tested-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx>
> [simplified code as requested by Alan Stern and Felipe Balbi]
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
...
> @@ -475,9 +492,16 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
> list_del(&udc->list);
> mutex_unlock(&udc_lock);
>
> - if (udc->driver)
> + if (udc->driver) {
> + struct usb_gadget_driver *driver = udc->driver;
> +
> usb_gadget_remove_driver(udc);
>
> + mutex_lock(&udc_lock);
> + list_add(&driver->pending, &gadget_driver_pending_list);
> + mutex_unlock(&udc_lock);
> + }
It looks like there is a race here with usb_gadget_unregister_driver().
Would it be okay to hold the udc_lock mutex throughout the whole "if"
statement?
Alan Stern
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