Re: [PATCH v3 2/7] xen/pciback: Don't deadlock when unbinding.

Konrad Rzeszutek Wilk
2014-07-09T14:13:26Z

On Wed, Jul 09, 2014 at 01:21:12PM +0100, David Vrabel wrote:
> On 08/07/14 19:58, konrad@kernel.org wrote:
> > --- a/drivers/xen/xen-pciback/pci_stub.c
> > +++ b/drivers/xen/xen-pciback/pci_stub.c
> > @@ -277,10 +277,15 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
> > * (so it's ready for the next domain)
> > */
> >
> > - /* This is OK - we are running from workqueue context
> > - * and want to inhibit the user from fiddling with 'reset'
> > + /* We might be holding the PCI lock (see comment at the top of the
> > + * function) - as such try lock and if we can't then don't worry -
> > + * as either:
> > + * - we are 'unbind' in which case 'pcistub_device_release' gets
> > + * called which does the locked version of this.
> > + * - the toolstack has the smarts to do it and has done the
> > + * reset on SysFS before assigning this device to another guest.
> > */
> > - pci_reset_function(dev);
> > + pci_try_reset_function(dev);
>
> Why not use __pci_reset_function_locked() and ensure all callers of
> pcistub_put_pci_dev() are holding the device lock?

That could also be done.
>
> > pci_restore_state(dev);
>
> If we didn't reset the device there is no need to restore its state.

<nods>
>
> David