[PATCH] PCI: Move device_del() from pci_stop_dev() to pci_destroy_dev()

[Rafael J. Wysocki]

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

After commit bcdde7e221a8 (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: fuse hidp af_packet xt_tcpudp xt_pkttype xt_LOG xt_limit ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables xt_conntrack nf_conntrack rfcomm ip6table_filter bnep ip6_tables x_tables arc4 ath9k mac80211 x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul iTCO_wdt crc32c_intel iTCO_vendor_support ghash_clmulni_intel aesni_intel ablk_helper acer_wmi sparse_keymap ath9k_common ath9k_hw cryptd lrw gf128mul ath3k glue_helper aes_x86_64 btusb microcode ath pcspkr joydev uvcvideo serio_raw videobuf2_core i2c_i801 videodev snd_hda_codec_hdmi cfg80211 videobuf2_vmalloc tg3 videobuf2_memops sg ptp pps_core lpc_ich mfd_core snd_hda_codec_realtek bluetooth hid_logitech_dj rfkill snd_hda_intel snd_hda_codec shpchp battery ac wmi acpi_cpufreq edd snd_usb_audio snd_pcm snd_page_alloc snd_hwdep snd_usbmidi_lib 
snd_rawmidi snd_seq snd_timer snd_seq_device snd soundcore autofs4 xhci_hcd processor scsi_dh_hp_sw scsi_dh_rdac scsi_dh_emc scsi_dh_alua scsi_dh
 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 lead 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#c6
Reported-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 drivers/pci/remove.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/pci/remove.c
===================================================================
--- linux-pm.orig/drivers/pci/remove.c
+++ linux-pm/drivers/pci/remove.c
@@ -24,7 +24,7 @@ static void pci_stop_dev(struct pci_dev
 	if (dev->is_added) {
 		pci_proc_detach_device(dev);
 		pci_remove_sysfs_dev_files(dev);
-		device_del(&dev->dev);
+		device_release_driver(&dev->dev);
 		dev->is_added = 0;
 	}
 
@@ -34,6 +34,8 @@ static void pci_stop_dev(struct pci_dev
 
 static void pci_destroy_dev(struct pci_dev *dev)
 {
+	device_del(&dev->dev);
+
 	down_write(&pci_bus_sem);
 	list_del(&dev->bus_list);
 	up_write(&pci_bus_sem);

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