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

David Vrabel
2014-07-09T12:21:16Z

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?

> pci_restore_state(dev);

If we didn't reset the device there is no need to restore its state.

David