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Message-ID: <2098030.vsbrD30xN4@vostro.rjw.lan>
Date: Mon, 25 Nov 2013 12:22:12 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Yinghai Lu <yinghai@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Tejun Heo <tj@...nel.org>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: Move device_del() from pci_stop_dev() to pci_destroy_dev()
On Sunday, November 24, 2013 08:54:12 PM Yinghai Lu wrote:
> On Sat, Nov 23, 2013 at 4:17 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > 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@...ux.intel.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> > 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);
> >
>
> Maybe that is not enough. could still need add is_removed ...
Well, is_removed is only used by pci_destroy_dev() in your patch, right?
That means its only role is to protect the device from being destroyed
twice (or more times) in a row, but that surely would be a bug? I don't
see how that can legitimately happen at least, so what exactly is the
scenario?
> Please check
>
> https://lkml.org/lkml/2013/5/13/653
> PATCH 3/7] PCI: Detach driver in pci_stop_device
It looks like there are more patches needed to apply this one.
Thanks!
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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