Re: USB: serial: port lifetimes (was: Re: USB Ooops PL2303 when unplug while use (linux v3.7.3))

[Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>]

On Fri, Feb 22, 2013 at 12:35:32PM -0500, Alan Stern wrote:
> On Fri, 22 Feb 2013, Johan Hovold wrote:
> 
> > > > So we end up with an unregistered device still possibly referenced by
> > > > tty instead, and I suspect we can't do much else than deal with any
> > > > post-disconnect callbacks. [ These should be few, especially with my
> > > > latest TTY-patches applied. ]
> > > > 
> > > > Alan, do you see any way around this? It's not possible (or desirable)
> > > > to pin the parent device (interface) until the last reference is
> > > > dropped, is it?
> > > 
> > > On the contrary, it is customary to pin data structures until the last 
> > > reference to them is gone.  That's what krefs are for.
> > 
> > I was referring to the usb device in the device hierarchy, which
> > apparently is not pinned despite the outstanding reference we have in
> > struct usb_serial.
> 
> Are you talking about the usb_device or the usb_interface?  The
> usb_serial structure _does_ pin the usb_device structure.  But it
> doesn't pin the usb_interface.  I don't know why things were done this
> way; maybe it's a mistake.

Ick, yeah, that was a mistake, probably been there since the very
beginning, sorry about that.

greg k-h
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