On Fri, Jul 31, 2020 at 02:06:20PM +0000, Peter Chen wrote:
> On 20-07-31 14:25:20, Greg Kroah-Hartman wrote:
> > On Fri, Jul 31, 2020 at 12:11:32PM +0000, Peter Chen wrote:
> >
> > Grab a reference from somewhere else and do not give it up for a long
> > time.
> >
>
> So wait_for_completion_timeout is suitable?
NO!!!
> The similar use case is when
> we open the file at the USB Drive at Windows, and we click "Eject", it
> will say "The device is currently in use", and refuse our "Eject"
> operation.
>
> When we try to remove the gadget, if the gadget is in use, we could
> refuse the remove operation, reasonable?
Nope. Remove it please.
> > > > > -static void usb_udc_nop_release(struct device *dev)
> > > > > +static void usb_gadget_release(struct device *dev)
> > > > > {
> > > > > + struct usb_gadget *gadget;
> > > > > +
> > > > > dev_vdbg(dev, "%s\n", __func__);
> > > > > +
> > > > > + gadget = container_of(dev, struct usb_gadget, dev);
> > > > > + complete(&gadget->done);
> > > > > + memset(dev, 0x0, sizeof(*dev));
> > > >
> > > > No, the memory should be freed here, not memset.
> > > >
> > >
> > > This memory is allocated at UDC driver and is freed by UDC driver too.
> >
> > That's wrong, the release function should be where this is released.
>
> So, the release function should be at individual UDC driver, a common
> release function is improper, right?
Depends on how this all works, but again, the release function needs to
free the memory, otherwise this is broken.
> > And this no-op function is horrid. There used to be documentation in
> > the kernel where I could rant about this, but instead, I'll just say,
> > "why are people trying to work around warnings we put in the core kernel
> > to fix common problems? Do they think we did that just because we
> > wanted to be mean???"
> >
>
> So, like kernel doc for device_initialize said, a proper fix for dwc3
> should be zeroed gadget device memory at its own driver before the
> gadget device register to driver core, right?
It should get a totally different, dynamically allocated structure.
NEVER recycle them.
thanks,
greg k-h
