| Message ID | 20121207062559.11051.18764.stgit@amt.stowe (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c index d890322..f9be8fb 100644 --- a/drivers/acpi/pci_root.c +++ b/drivers/acpi/pci_root.c @@ -644,6 +644,8 @@ static int acpi_pci_root_start(struct acpi_device *device) struct acpi_pci_root *root = acpi_driver_data(device); struct acpi_pci_driver *driver; + pci_bus_add_devices(root->bus); + mutex_lock(&acpi_pci_root_lock); list_for_each_entry(driver, &acpi_pci_drivers, node) if (driver->add) @@ -651,8 +653,6 @@ static int acpi_pci_root_start(struct acpi_device *device) acpiphp_add_bridge(root); mutex_unlock(&acpi_pci_root_lock); - pci_bus_add_devices(root->bus); - return 0; }
During early boot, the kernel performs ACPI enumeration in which host bridges are discovered (subsys_initcall(acpi_pci_root_init)). Later drivers, both built-in and modules such as the "ACPI PCI Slot Detection Driver ("pci_slot")", are loaded (module_init(acpi_pci_slot_init)) thus we end up with the following call chain: acpi_pci_root_start list_for_each_entry(..., acpi_pci_drivers, ...) driver->add(root) # always no-op; list empty pci_bus_add_devices acpi_pci_slot_init # module_init acpi_pci_register_driver(acpi_pci_slot_driver) list_for_each_entry(..., &acpi_pci_roots, ...) driver->add(root) # acpi_pci_slot_add() Note that for host bridges present at boot time the 'acpi_pci_drivers' list is always empty when acpi_pci_root_start() runs. However, during a Host Bridge hot-add event, the "pci_slot" sub-driver is already on the 'acpi_pci_drivers' list and we end up calling acpi_pci_slot_add() before pci_bus_add_devices() and encounter the following refcount WARNING: calling acpi_pci_slot_add(): pci_bus 0000:03: dev 00, created physical slot 1 ------------[ cut here ]------------ WARNING: at include/linux/kref.h:42 kobject_get+0x32/0x40() Call Trace: [<ffffffff812541d2>] kobject_get+0x32/0x40 [<ffffffff8133f0f9>] get_device+0x19/0x20 [<ffffffff812d9f11>] register_slot+0x216/0x26d [<ffffffff812ce92f>] acpi_walk_namespace+0x8a/0xc4 [<ffffffff812d9cb9>] walk_p2p_bridge+0xf1/0x133 [<ffffffff812ce92f>] acpi_walk_namespace+0x8a/0xc4 [<ffffffff812d9b71>] acpi_pci_slot_add+0xe0/0x137 [<ffffffff812b8705>] acpi_pci_root_start+0x3e/0x59 This patch fixes this latent issue by moving up pci_bus_add_devices() so that the refcount will be initialized before subsequent references, via driver additions from the 'acpi_pci_drivers' list, occur. Signed-off-by: Myron Stowe <myron.stowe@redhat.com> --- drivers/acpi/pci_root.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html