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Date:	Mon, 7 Dec 2015 19:08:50 +0800
From:	Lu Baolu <>
To:	Peter Wu <>
Subject: Re: (4.3.0) r8152: deadlock related to runtime suspend?

On 12/07/2015 05:37 PM, Peter Wu wrote:
> On Mon, Dec 07, 2015 at 05:11:50PM +0800, Lu Baolu wrote:
>> Hi Peter,
>> Have you ever tried disabling auto-pm? Did things go smoothly if auto-pm is disabled?
>> I always disable usb auto-pm in below way.
>> # echo on | tee /sys/bus/usb/devices/*/power/control
>> # echo on > /sys/bus/pci/devices/<bus_name>/power/control
>> Thanks,
>> Baolu
> Hi Baolu,
> The deadlock does not seem to occur with auto-PM disabled, but that is a
> workaround for the issue. The hang can always be reproduced under this
> test:
>  - Start a QEMU VM, passing through the USB adapter

I would suggest you to start with bare metal.

When you pass through the host controller to a guest VM, you
probably use IOMMU unit to let hardware access the memory
directly, but things like pci configure space access, interrupt and
IO port access still rely on QEMU. This introduces a lot of complexities.


>  - This VM boots to a busybox shell with no other services running or
>    udev magic (to reduce interference).
>  - Enable runtime PM for all devices by default (see script below)
>  - From the console, invoke "ip link set eth1 up" (eth0 is a virtio
>    adapter).
>     # somewhere in /init after mounting filesystems
>     echo /sbin/hotplug > /proc/sys/kernel/hotplug
>     echo auto | tee  /sys/bus/pci/devices/*/power/control \
>         /sys/bus/usb/devices/*/power/control >/dev/null
>     #!/bin/sh
>     # /sbin/hotplug
>     path="/sys/$DEVPATH/power/control"
>     [ -e "$path" ] || return
>     newval=auto
>     read status < "$path"
>     if [ "x$status" != "x$newval" ]; then
>         echo "$DEVPATH: $status -> $newval" >/dev/kmsg
>         echo $newval > "$path"
>     fi
> With "auto", the ip command hangs (a trace can be found on the bottom of
> this mail). With "on", it does not.
> If I keep a loop spinning that invokes `ethtool eth1`, the command
> returns immediately without issues (presumably because the device is not
> suspended through runtime PM).
> Under some circumstances I get a lockdep warning (when trying to bring
> an interface down if I remember correctly). Its trace can be found on
> the bottom of this mail.
> I'll keep testing. For the lockdep warning, my initial guess is that
> calling schedule_delayed_work_sync under tp->lock is a bad idea because
> scheduled work can execute and try to claim tp->lock too.
> Maybe there are two different lockup cases here, I'll keep testing.
> Kind regards,
> Peter
>> On 12/05/2015 06:59 PM, Peter Wu wrote:
>>> Hi,
>>> I rarely use a Realtek USB 3.0 Gigabit Ethernet adapter (vid/pid
>>> 0bda:8153), but when I did last night, it resulted in a lockup of
>>> processes doing networking ("ip link", "ping", "ethtool", ...).
>>> A (few) minute(s) before that event, I noticed that there was no network
>>> connectivity (ping hung) which was somehow solved by invoking "ethtool
>>> eth1" (triggering runtime pm wakeup?). This same trick did not work at
>>> the next event. Invoking "ethtool eth1", "ip link", etc. hung completely
>>> and interrupt (^C) did not work at all.
>>> Since that did not work, I pulled the USB adapter and re-inserted it,
>>> hoping it would reset things. That did not work at all, there was a
>>> "usb disconnect" message, but no further driver messages.
>>> Fast forward an hour, and it has become a disaster. I have terminated
>>> and killed many programs via SysRq but am still unable to get a stable
>>> system that does not hang on network I/O. Even the suspend process
>>> fails so in the end I attempted to shutdown the system. After half an
>>> hour after getting the poweroff message, I issued SysRq + B to reboot
>>> (since SysRq + O did not shut down either).
>>> Attached are logs with various various backtraces from SysRq and failed
>>> suspend. Let me know if you need more information!
>>> By the way, often I have to rmmod xhci and re-insert it, otherwise
>>> plugging it in does not result in a detection. A USB 2.0 port does not
>>> have this problem (runtime PM is enabled for all devices). This is the
>>> USB 3.0 port:
>>>     02:00.0 USB controller [0c03]: NEC Corporation uPD720200 USB 3.0
>>>     Host Controller [1033:0194] (rev 03)

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