• Rafael J. Wysocki's avatar
    PCI: Move device_del() from pci_stop_dev() to pci_destroy_dev() · 4bff6749
    Rafael J. Wysocki authored
    After commit bcdde7e2 (sysfs: make __sysfs_remove_dir() recursive)
    I'm seeing traces analogous to the one below in Thunderbolt testing:
    
    WARNING: CPU: 3 PID: 76 at /scratch/rafael/work/linux-pm/fs/sysfs/group.c:214 sysfs_remove_group+0x59/0xe0()
     sysfs group ffffffff81c6c500 not found for kobject '0000:08'
     Modules linked in: ...
     CPU: 3 PID: 76 Comm: kworker/u16:7 Not tainted 3.13.0-rc1+ #76
     Hardware name: Acer Aspire S5-391/Venus    , BIOS V1.02 05/29/2012
     Workqueue: kacpi_hotplug acpi_hotplug_work_fn
      0000000000000009 ffff8801644b9ac8 ffffffff816b23bf 0000000000000007
      ffff8801644b9b18 ffff8801644b9b08 ffffffff81046607 ffff88016925b800
      0000000000000000 ffffffff81c6c500 ffff88016924f928 ffff88016924f800
     Call Trace:
      [<ffffffff816b23bf>] dump_stack+0x4e/0x71
      [<ffffffff81046607>] warn_slowpath_common+0x87/0xb0
      [<ffffffff810466d1>] warn_slowpath_fmt+0x41/0x50
      [<ffffffff811e42ef>] ? sysfs_get_dirent_ns+0x6f/0x80
      [<ffffffff811e5389>] sysfs_remove_group+0x59/0xe0
      [<ffffffff8149f00b>] dpm_sysfs_remove+0x3b/0x50
      [<ffffffff81495818>] device_del+0x58/0x1c0
      [<ffffffff814959c8>] device_unregister+0x48/0x60
      [<ffffffff813254fe>] pci_remove_bus+0x6e/0x80
      [<ffffffff81325548>] pci_remove_bus_device+0x38/0x110
      [<ffffffff8132555d>] pci_remove_bus_device+0x4d/0x110
      [<ffffffff81325639>] pci_stop_and_remove_bus_device+0x19/0x20
      [<ffffffff813418d0>] disable_slot+0x20/0xe0
      [<ffffffff81341a38>] acpiphp_check_bridge+0xa8/0xd0
      [<ffffffff813427ad>] hotplug_event+0x17d/0x220
      [<ffffffff81342880>] hotplug_event_work+0x30/0x70
      [<ffffffff8136d665>] acpi_hotplug_work_fn+0x18/0x24
      [<ffffffff81061331>] process_one_work+0x261/0x450
      [<ffffffff81061a7e>] worker_thread+0x21e/0x370
      [<ffffffff81061860>] ? rescuer_thread+0x300/0x300
      [<ffffffff81068342>] kthread+0xd2/0xe0
      [<ffffffff81068270>] ? flush_kthread_worker+0x70/0x70
      [<ffffffff816c19bc>] ret_from_fork+0x7c/0xb0
      [<ffffffff81068270>] ? flush_kthread_worker+0x70/0x70
    
    (Mika Westerberg sees them too in his tests).
    
    Some investigation documented in kernel bug #65281 led me to the
    conclusion that the source of the problem is the device_del() in
    pci_stop_dev() as it now causes the sysfs directory of the device to be
    removed recursively along with all of its subdirectories.  That includes
    the sysfs directory of the device's subordinate bus (dev->subordinate) and
    its "power" group.
    
    Consequently, when pci_remove_bus() is called for dev->subordinate in
    pci_remove_bus_device(), it calls device_unregister(&bus->dev), but at this
    point the sysfs directory of bus->dev doesn't exist any more and its
    "power" group doesn't exist either.  Thus, when dpm_sysfs_remove() called
    from device_del() tries to remove that group, it triggers the above
    warning.
    
    That indicates a logical mistake in the design of
    pci_stop_and_remove_bus_device(), which causes bus device objects to be
    left behind their parents (bridge device objects) and can be fixed by
    moving the device_del() from pci_stop_dev() into pci_destroy_dev(), so
    pci_remove_bus() can be called for the device's subordinate bus before the
    device itself is unregistered from the hierarchy.  Still, the driver, if
    any, should be detached from the device in pci_stop_dev(), so use
    device_release_driver() directly from there.
    
    References: https://bugzilla.kernel.org/show_bug.cgi?id=65281#c6Reported-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
    4bff6749
remove.c 3.3 KB