On Mon, Sep 18, 2017 at 08:53:45PM -0500, Stuart Hayes wrote:
> Bjorn et al,
>
> I'm hoping to enhance network device naming in systemd to parse
> sysfs "virtfn%u" and "physfn" links, so it understands virtual
> devices.
>
> I've noticed that the udev event which triggers the
> systemd/biosdevname network device naming--the udev "add" event for
> the network device, which happens within pci_bus_add_device() when
> the network driver's probe function calls register_netdev()--occurs
> before the sysfs links "physfn" and "virtfn%u" are created. This
> creates a race when the network naming code tries to look at those
> links (something biosdevname already does).
>
> Is there any reason why we couldn't switch the order of those calls
> to eliminate the race, as shown in the patch below? I couldn't
> think of any, since those links apply to the pci subsystem devices
> in sysfs (which are already created), not the net subsystem devices.
> I'd be happy to submit a patch if that looks ok.
Seems plausible. I think the sequence you're describing is this:
pci_iov_add_virtfn
pci_bus_add_device
pci_create_sysfs_dev_files
device_attach
...
register_netdev
...
# udev "add" event
sysfs_create_link("virtfn%u)
sysfs_create_link("physfn")
kobject_uevent(KOBJ_CHANGE)
We create most of the sysfs files before attaching the driver, and it
makes sense to me that we should set up the IOV sysfs files as well.
Bjorn
> --- linux-4.14-rc1/drivers/pci/iov.c.orig 2017-09-18 15:00:43.168255665 -0500
> +++ linux-4.14-rc1/drivers/pci/iov.c 2017-09-18 15:07:04.792280999 -0500
> @@ -162,7 +162,6 @@ int pci_iov_add_virtfn(struct pci_dev *d
>
> pci_device_add(virtfn, virtfn->bus);
>
> - pci_bus_add_device(virtfn);
> sprintf(buf, "virtfn%u", id);
> rc = sysfs_create_link(&dev->dev.kobj, &virtfn->dev.kobj, buf);
> if (rc)
> @@ -173,6 +172,8 @@ int pci_iov_add_virtfn(struct pci_dev *d
>
> kobject_uevent(&virtfn->dev.kobj, KOBJ_CHANGE);
>
> + pci_bus_add_device(virtfn);
> +
> return 0;
>
> failed2:
>
>
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