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Subject[PATCH v2 3/3] PCI: pci_slot: grab refcount on slot's bus
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If a logical hot unplug (remove) is performed on a physical PCI slot's
parent bridge, and then pci_slot is unloaded, we will encounter an oops:

[<ffffffff803a788a>] kobject_release+0x9a/0x290
[<ffffffff803a77f0>] ? kobject_release+0x0/0x290
[<ffffffff803a8ce7>] kref_put+0x37/0x80
[<ffffffff803a76f7>] kobject_put+0x27/0x60
[<ffffffff803bebcc>] ? pci_destroy_slot+0x3c/0xc0
[<ffffffff803bebd5>] pci_destroy_slot+0x45/0xc0
[<ffffffffa000f05c>] acpi_pci_slot_remove+0x5c/0x91 [pci_slot]
[<ffffffff8040064b>] acpi_pci_unregister_driver+0x4b/0x62
[<ffffffffa000f5c8>] acpi_pci_slot_exit+0x10/0x12 [pci_slot]
[<ffffffff80276ce1>] sys_delete_module+0x161/0x250
We need to grab a reference to the parent PCI bus, which will pin
the bus and prevent it from being released until pci_slot is unloaded.

Cc: lenb@kernel.org
Reported-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
---
drivers/acpi/pci_slot.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/drivers/acpi/pci_slot.c b/drivers/acpi/pci_slot.c
index cd1f446..12158e0 100644
--- a/drivers/acpi/pci_slot.c
+++ b/drivers/acpi/pci_slot.c
@@ -164,6 +164,8 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
list_add(&slot->list, &slot_list);
mutex_unlock(&slot_list_lock);

+ get_device(&pci_bus->dev);
+
dbg("pci_slot: %p, pci_bus: %x, device: %d, name: %s\n",
pci_slot, pci_bus->number, device, name);

@@ -310,12 +312,15 @@ static void
acpi_pci_slot_remove(acpi_handle handle)
{
struct acpi_pci_slot *slot, *tmp;
+ struct pci_bus *pbus;

mutex_lock(&slot_list_lock);
list_for_each_entry_safe(slot, tmp, &slot_list, list) {
if (slot->root_handle == handle) {
list_del(&slot->list);
+ pbus = slot->pci_slot->bus;
pci_destroy_slot(slot->pci_slot);
+ put_device(&pbus->dev);
kfree(slot);
}
}


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