Re: [Xen-devel] [PATCH] xen/pci: make bus notifier handler return sane values

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

On Wed, Aug 17, 2011 at 09:32:32AM +0100, Jan Beulich wrote:
> Notifier functions are expected to return NOTIFY_* codes, not -E...
> ones. In particular, since the respective hypercalls failing is not
> fatal to the operation of the Dom0 kernel, it must be avoided to

So if we fail adding a PCI device, won't we be unable to actually
setup its MSI?

> return negative values here as those would make it appear as if
> NOTIFY_STOP_MASK wa set, suppressing further notification calls to
> other interested parties (which is also why we don't want to use
> notifier_from_errno() here).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> 
> ---
>  drivers/xen/pci.c |   11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> --- 3.1-rc2/drivers/xen/pci.c
> +++ 3.1-rc2-xen-pci-bus-notifier/drivers/xen/pci.c
> @@ -86,23 +86,22 @@ static int xen_pci_notifier(struct notif
>                           unsigned long action, void *data)
>  {
>       struct device *dev = data;
> -     int r = 0;
>  
>       switch (action) {
>       case BUS_NOTIFY_ADD_DEVICE:
> -             r = xen_add_device(dev);
> +             xen_add_device(dev);
>               break;
>       case BUS_NOTIFY_DEL_DEVICE:
> -             r = xen_remove_device(dev);
> +             xen_remove_device(dev);
>               break;
>       default:
> -             break;
> +             return NOTIFY_DONE;
>       }
>  
> -     return r;
> +     return NOTIFY_OK;
>  }
>  
> -struct notifier_block device_nb = {
> +static struct notifier_block device_nb = {
>       .notifier_call = xen_pci_notifier,
>  };
>  
> 
> 
> 

> Notifier functions are expected to return NOTIFY_* codes, not -E...
> ones. In particular, since the respective hypercalls failing is not
> fatal to the operation of the Dom0 kernel, it must be avoided to
> return negative values here as those would make it appear as if
> NOTIFY_STOP_MASK wa set, suppressing further notification calls to
> other interested parties (which is also why we don't want to use
> notifier_from_errno() here).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> 
> ---
>  drivers/xen/pci.c |   11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> --- 3.1-rc2/drivers/xen/pci.c
> +++ 3.1-rc2-xen-pci-bus-notifier/drivers/xen/pci.c
> @@ -86,23 +86,22 @@ static int xen_pci_notifier(struct notif
>                           unsigned long action, void *data)
>  {
>       struct device *dev = data;
> -     int r = 0;
>  
>       switch (action) {
>       case BUS_NOTIFY_ADD_DEVICE:
> -             r = xen_add_device(dev);
> +             xen_add_device(dev);
>               break;
>       case BUS_NOTIFY_DEL_DEVICE:
> -             r = xen_remove_device(dev);
> +             xen_remove_device(dev);
>               break;
>       default:
> -             break;
> +             return NOTIFY_DONE;
>       }
>  
> -     return r;
> +     return NOTIFY_OK;
>  }
>  
> -struct notifier_block device_nb = {
> +static struct notifier_block device_nb = {
>       .notifier_call = xen_pci_notifier,
>  };
>  

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