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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jul 09, 2014 at 01:21:12PM +0100, David Vrabel wrote:
> On 08/07/14 19:58, konrad@xxxxxxxxxx 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

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