Re: [PATCH] driver core: unbind consumers before locking parent on device unbind

From: Lucas Stach
Date: Fri Feb 17 2017 - 13:47:05 EST

Am Freitag, den 17.02.2017, 10:42 -0800 schrieb Greg Kroah-Hartman:
> On Fri, Feb 17, 2017 at 07:36:29PM +0100, Lucas Stach wrote:
> > On forced unbind the parent lock is taken, as the device might be a USB
> > device. The device to be unbound might have active consumers, which
> > must be unbound before calling device_release_driver(), otherwise this
> > function might deadlock when trying to take the parent lock during
> > consumer unbind.
> Really? What type of device does this fail on today?

Regular devices on a MMIO bus. __device_release_driver() will take the
parent lock unconditionally when it unbinds consumer devices. So if the
forced unbound device is on the same bus as the consumer we will
deadlock right there.