Re: [PATCH v3 02/14] PCI: prevent duplicate slot names

[Kenji Kaneshige]

Alex-san,

Alex Chiang wrote:
> * Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>:
> > Kenji Kaneshige wrote:
> > > Hi Alex-san,
> > >
> > > Here is one comment, though I have not finished reviewing/testing
> > > your patches yet (sorry for the delay).
> > >
> > > Alex Chiang wrote:
> > >
> > > (snip.)
> > >
> > > > diff --git a/drivers/pci/hotplug/pci_hotplug_core.c  
> > > > b/drivers/pci/hotplug/pci_hotplug_core.c
> > > > index 3e37d63..46802dc 100644
> > > > --- a/drivers/pci/hotplug/pci_hotplug_core.c
> > > > +++ b/drivers/pci/hotplug/pci_hotplug_core.c
> > > > @@ -570,39 +570,32 @@ int pci_hp_register(struct hotplug_slot *slot,  
> > > > struct pci_bus *bus, int slot_nr,
> > > >          return -EINVAL;
> > > >      }
> > > >  -    /* Check if we have already registered a slot with the same 
> > > > name. */
> > > > -    if (get_slot_from_name(name))
> > > > -        return -EEXIST;
> > > > -
> > > >      /*
> > > > -     * No problems if we call this interface from both ACPI_PCI_SLOT
> > > > -     * driver and call it here again. If we've already created the
> > > > -     * pci_slot, the interface will simply bump the refcount.
> > > > +     * Look for existing slot. If we find it, and it was created by a
> > > > +     * slot detection driver (ie, doesn't have a ->hotplug()) then we
> > > > +     * allow the hotplug driver calling us to rename the slot if  
> > > > desired.
> > > > +     *
> > > > +     * Otherwise, create the slot and carry on with life.
> > > >       */
> > > > -    pci_slot = pci_create_slot(bus, slot_nr, name);
> > > > -    if (IS_ERR(pci_slot))
> > > > -        return PTR_ERR(pci_slot);
> > > > -
> > > > -    if (pci_slot->hotplug) {
> > > > -        dbg("%s: already claimed\n", __func__);
> > > > -        pci_destroy_slot(pci_slot);
> > > > -        return -EBUSY;
> > > > +    pci_slot = pci_get_pci_slot(bus, slot_nr);
> > > The pci_get_pci_slot() function refers pci_bus->slots list, so it
> > > should be called with pci_bus_sem semaphore held as pci_create_slot()
> > > does, or pci_bus_sem semaphore should be held by pci_get_pci_slot()
> > > itself.
>
> Yes, I've changed pci_get_pci_slot() to acquire the pci_bus_sem
> semaphore.
>
> Thank you for pointing this out.
>
> It will be fixed in v4 of this patch series, which I will send
> out after I receive the rest of your review comments.

I noticed that changing pci_get_pci_slot() to acquire the pci_bus_sem
might be not enough. If slot was created between pci_get_pci_slot() and
pci_create_slot() by another thread in the following code, something
wrong would happen I think.

       pci_slot = pci_get_pci_slot(bus, slot_nr);
       if (pci_slot) {
               if (pci_slot->hotplug) {
                       result = -EBUSY;
                       goto err;
               }

               if (strcmp(kobject_name(&pci_slot->kobj), name))
                       if ((result = pci_rename_slot(pci_slot, name)))
                               goto err;
       } else {
               pci_slot = pci_create_slot(bus, slot_nr, name);
               if ((result = IS_ERR(pci_slot)))
                       goto out;
       }

I've finished reviewing and testing your patches. The rest of your
patch looks good to me. Of course, we must not forget the comment
from Taku Izumi.

Thanks,
Kenji Kaneshige



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