netdev - Re: [PATCH 1/7] uio: add module owner to prevent inappropriate module unloading

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Date:	Thu, 15 Aug 2013 10:13:14 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Benedikt Spranger <b.spranger@...utronix.de>,
	netdev@...r.kernel.org,
	Alexander Frank <Alexander.Frank@...rspaecher.com>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Holger Dengler <dengler@...utronix.de>
Subject: Re: [PATCH 1/7] uio: add module owner to prevent inappropriate
 module unloading

On Thu, Aug 15, 2013 at 06:54:46PM +0200, Sebastian Andrzej Siewior wrote:
> On 08/15/2013 06:42 PM, Greg Kroah-Hartman wrote:
> >> For this to happen you would need a refcount in uio-core which learns
> >> that the device is gone and does not invoke any callbacks because the
> >> device is gone. Something like you have in USB where you return 0 on
> >> reads from ttyUSB after someone pulled the cable.
> > 
> > That happens because we invalidate the filehandle in the tty layer by
> > tearing everything down in the usb serial driver.  And yes, uio also
> > needs to do the same thing, if it doesn't already.
> 
> Ah. Do you have a handy pointer where / how you do this?

The tty layer isn't exactly "handy" :)

Somewhere we send a HANGUP signal to userspace, and I think we
invalidate the file handle somehow, it's been years since I last looked
at that code, sorry.

greg k-h
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