Alex Chiang wrote:
Hi Kenji-san,
* Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>:
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'm sorry, I don't think I see the problem you are pointing out.
If pci_get_pci_slot() finds a pci_slot, we do not modify
pci_bus->slots any further, so even if a new slot is created, it
shouldn't affect the pci_slot that we already found.
I must be missing something, but I don't know what. Would you
mind explaining what you had in mind with your comment?
Here is one of the example of the problem I imagine.
When pci_get_pci_slot() does NOT find a pci_slot, pci_hp_register()
calls pci_create_slot(). If another hotplug driver creates slot
between pci_get_pci_slot() and pci_create_slot(), hotplug member of
pci_slot returned from pci_create_slot() is not NULL in the following
code.
pci_slot = pci_create_slot(bus, slot_nr, name);
if ((result = IS_ERR(pci_slot)))
goto out;
In this case, we should return with -EBUSY. But because there is no
check to see if pci->slot is NULL, pci_slot->hotplug will be overwritten
with the new value.
Thanks,
Kenji Kaneshige
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