[PATCH][tentative] PCI / ACPI: Rework PCI host bridge removal to avoid sysfs warnings

From: Rafael J. Wysocki
Date: Sat Dec 28 2013 - 18:06:58 EST

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

The device_del(&host_bridge->dev) in pci_stop_root_bus() is
problematic, because it causes all sysfs directories below
the host bridge to be removed recursively and when
pci_remove_root_bus() attempts to remove devices on the root
bus (whose sysfs directories are gone now along with all their
subdirectories), it causes warnings similar to this one to be

WARNING: CPU: 0 PID: 6 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0()
sysfs group ffffffff819ac5c0 not found for kobject '0001:ff:10.2'
Modules linked in: <irrelevant list>
CPU: 0 PID: 6 Comm: kworker/u512:0 Tainted: G W 3.13.0-rc5+ #11
Hardware name:
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
0000000000000009 ffff8808738d3bd8 ffffffff815d84ea ffff8808738d3c20
ffff8808738d3c10 ffffffff8106594d 0000000000000000 ffffffff819ac5c0
ffff880871b9d0a8 ffff8a07d1895000 0000000000000103 ffff8808738d3c70
Call Trace:
[<ffffffff815d84ea>] dump_stack+0x45/0x56
[<ffffffff8106594d>] warn_slowpath_common+0x7d/0xa0
[<ffffffff810659bc>] warn_slowpath_fmt+0x4c/0x50
[<ffffffff8122b52e>] ? sysfs_get_dirent_ns+0x4e/0x70
[<ffffffff8122c806>] sysfs_remove_group+0xc6/0xd0
[<ffffffff813b83f3>] dpm_sysfs_remove+0x43/0x50
[<ffffffff813ae105>] device_del+0x45/0x1c0
[<ffffffff812e51f6>] pci_remove_bus_device+0x66/0xd0
[<ffffffff812e5363>] pci_remove_root_bus+0x73/0x80
[<ffffffff813276ab>] acpi_pci_root_remove+0x42/0x4f
[<ffffffff81323070>] acpi_bus_trim+0x56/0x89
[<ffffffff81323052>] acpi_bus_trim+0x38/0x89
[<ffffffff813245df>] acpi_device_hotplug+0x137/0x33b
[<ffffffff8131efba>] acpi_hotplug_work_fn+0x1c/0x27
[<ffffffff81080f1b>] process_one_work+0x17b/0x460
[<ffffffff81081ccb>] worker_thread+0x11b/0x400
[<ffffffff81081bb0>] ? rescuer_thread+0x3e0/0x3e0
[<ffffffff81088a12>] kthread+0xd2/0xf0
[<ffffffff81088940>] ? kthread_create_on_node+0x180/0x180
[<ffffffff815e823c>] ret_from_fork+0x7c/0xb0
[<ffffffff81088940>] ? kthread_create_on_node+0x180/0x180

To avoid that, the host bridge device has to be deleted after all of
its children, so merge pci_stop_root_bus() and pci_remove_root_bus()
into one function, pci_stop_and_remove_root_bus(), that first will
use pci_stop_and_remove_bus_device() to stop and remove all devices
on the root bus and then will delete the host bridge device, remove
its bus and drop the final reference to it.

Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>


I can't really test this patch, but I don't know how it can break anything.

The only user of pci_stop_root_bus() and pci_remove_root_bus() is
acpi_pci_root_remove() and the code ordering there seems to be somewhat
arbitrary. If you are aware of any reason why it may not work, please let
me know. :-)


drivers/acpi/pci_root.c | 4 +---
drivers/pci/remove.c | 23 ++++-------------------
include/linux/pci.h | 3 +--
3 files changed, 6 insertions(+), 24 deletions(-)

Index: linux-pm/drivers/acpi/pci_root.c
--- linux-pm.orig/drivers/acpi/pci_root.c
+++ linux-pm/drivers/acpi/pci_root.c
@@ -611,12 +611,10 @@ static void acpi_pci_root_remove(struct
struct acpi_pci_root *root = acpi_driver_data(device);

- pci_stop_root_bus(root->bus);
device_set_run_wake(root->bus->bridge, false);

- pci_remove_root_bus(root->bus);
+ pci_stop_and_remove_root_bus(root->bus);

Index: linux-pm/drivers/pci/remove.c
--- linux-pm.orig/drivers/pci/remove.c
+++ linux-pm/drivers/pci/remove.c
@@ -114,7 +114,7 @@ void pci_stop_and_remove_bus_device(stru

-void pci_stop_root_bus(struct pci_bus *bus)
+void pci_stop_and_remove_root_bus(struct pci_bus *bus)
struct pci_dev *child, *tmp;
struct pci_host_bridge *host_bridge;
@@ -123,29 +123,14 @@ void pci_stop_root_bus(struct pci_bus *b

host_bridge = to_pci_host_bridge(bus->bridge);
- list_for_each_entry_safe_reverse(child, tmp,
- &bus->devices, bus_list)
- pci_stop_bus_device(child);
+ list_for_each_entry_safe_reverse(child, tmp, &bus->devices, bus_list)
+ pci_stop_and_remove_bus_device(child);

/* stop the host bridge */
-void pci_remove_root_bus(struct pci_bus *bus)
- struct pci_dev *child, *tmp;
- struct pci_host_bridge *host_bridge;
- if (!pci_is_root_bus(bus))
- return;
- host_bridge = to_pci_host_bridge(bus->bridge);
- list_for_each_entry_safe(child, tmp,
- &bus->devices, bus_list)
- pci_remove_bus_device(child);
+ /* remove the root bus */
host_bridge->bus = NULL;
/* remove the host bridge */
Index: linux-pm/include/linux/pci.h
--- linux-pm.orig/include/linux/pci.h
+++ linux-pm/include/linux/pci.h
@@ -779,8 +779,7 @@ struct pci_dev *pci_dev_get(struct pci_d
void pci_dev_put(struct pci_dev *dev);
void pci_remove_bus(struct pci_bus *b);
void pci_stop_and_remove_bus_device(struct pci_dev *dev);
-void pci_stop_root_bus(struct pci_bus *bus);
-void pci_remove_root_bus(struct pci_bus *bus);
+void pci_stop_and_remove_root_bus(struct pci_bus *bus);
void pci_setup_cardbus(struct pci_bus *bus);
void pci_sort_breadthfirst(void);
#define dev_is_pci(d) ((d)->bus == &pci_bus_type)

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