From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> After commit 1aeae82 (ACPI / PCI: avoid building pci_slot as module) the pci_slot driver's .add() callback routine, acpi_pci_slot_add(), is executed from within acpi_pci_root_add() before the PCI devices on the bus are enumerated and that triggers the WARN_ON() in kobject_get(): WARNING: at /scratch/rafael/work/test/include/linux/kref.h:42 kobject_get+0x33/0x40() Hardware name: PORTEGE R500 Modules linked in: Pid: 1, comm: swapper/0 Not tainted 3.8.0-rc7+ #160 Call Trace: [<ffffffff8103d38a>] warn_slowpath_common+0x7a/0xb0 [<ffffffff8103d3d5>] warn_slowpath_null+0x15/0x20 [<ffffffff812f99b3>] kobject_get+0x33/0x40 [<ffffffff81452b82>] get_device+0x12/0x30 [<ffffffff8138df7b>] register_slot+0x243/0x295 [<ffffffff810a7b6d>] ? trace_hardirqs_on+0xd/0x10 [<ffffffff8137b7b9>] acpi_ns_walk_namespace+0x10f/0x24a [<ffffffff8138dd38>] ? walk_p2p_bridge+0x13b/0x13b [<ffffffff8138dd38>] ? walk_p2p_bridge+0x13b/0x13b [<ffffffff8137bdc3>] acpi_walk_namespace+0xe9/0x132 [<ffffffff8138dd38>] ? walk_p2p_bridge+0x13b/0x13b [<ffffffff8138dcf5>] walk_p2p_bridge+0xf8/0x13b [<ffffffff8134d606>] ? acpi_os_signal_semaphore+0x76/0x87 [<ffffffff8138dd38>] ? walk_p2p_bridge+0x13b/0x13b [<ffffffff8137b7b9>] acpi_ns_walk_namespace+0x10f/0x24a [<ffffffff8138dbfd>] ? do_sta_before_sun+0x2b/0x2b [<ffffffff8138dbfd>] ? do_sta_before_sun+0x2b/0x2b [<ffffffff8137bdc3>] acpi_walk_namespace+0xe9/0x132 [<ffffffff81356071>] ? acpi_pci_root_add+0x3e7/0x49a [<ffffffff8138e07f>] acpi_pci_slot_add+0xb2/0x103 [<ffffffff8138dd38>] ? walk_p2p_bridge+0x13b/0x13b [<ffffffff81356089>] acpi_pci_root_add+0x3ff/0x49a which means that pci_bus->dev used in register_slot() has not been registered yet at that point. To fix this use the observation that before commit 1aeae82 acpi_pci_slot_add() was always run after pci_bus_add_devices() and that happened to the acpiphp's .add() callback routine too. Thus it is safe to reorder acpi_pci_root_add() to make the PCI root drivers' .add() callbacks be run after pci_bus_add_devices(), so do that. This approach was previously proposed by Myron Stowe. References: https://patchwork.kernel.org/patch/1848781/ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- The commit mentioned in the changelog above is in linux-pm.git/linux-next. Thanks, Rafael --- drivers/acpi/pci_root.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) Index: test/drivers/acpi/pci_root.c =================================================================== --- test.orig/drivers/acpi/pci_root.c +++ test/drivers/acpi/pci_root.c @@ -600,17 +600,20 @@ static int acpi_pci_root_add(struct acpi if (system_state != SYSTEM_BOOTING) pci_assign_unassigned_bus_resources(root->bus); + /* need to after hot-added ioapic is registered */ + if (system_state != SYSTEM_BOOTING) + pci_enable_bridges(root->bus); + + pci_bus_add_devices(root->bus); + mutex_lock(&acpi_pci_root_lock); + list_for_each_entry(driver, &acpi_pci_drivers, node) if (driver->add) driver->add(root); - mutex_unlock(&acpi_pci_root_lock); - /* need to after hot-added ioapic is registered */ - if (system_state != SYSTEM_BOOTING) - pci_enable_bridges(root->bus); + mutex_unlock(&acpi_pci_root_lock); - pci_bus_add_devices(root->bus); return 1; out_del_root: -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
