A toolstack may delete the vif frontend and backend xenstore entries
while xen-netfront is in the removal code path. In that case, the
checks for xenbus_read_driver_state would return XenbusStateUnknown, and
xennet_remove would hang indefinitely. This hang prevents system
shutdown.
xennet_remove must be able to handle XenbusStateUnknown, and
netback_changed must also wake up the wake_queue for that state as well.
Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
Signed-off-by: Jason Andryuk <[email protected]>
Cc: Eduardo Otubo <[email protected]>
---
drivers/net/xen-netfront.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 8328d395e332..3127bc8633ca 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2005,7 +2005,10 @@ static void netback_changed(struct xenbus_device *dev,
case XenbusStateInitialised:
case XenbusStateReconfiguring:
case XenbusStateReconfigured:
+ break;
+
case XenbusStateUnknown:
+ wake_up_all(&module_unload_q);
break;
case XenbusStateInitWait:
@@ -2136,7 +2139,9 @@ static int xennet_remove(struct xenbus_device *dev)
xenbus_switch_state(dev, XenbusStateClosing);
wait_event(module_unload_q,
xenbus_read_driver_state(dev->otherend) ==
- XenbusStateClosing);
+ XenbusStateClosing ||
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateUnknown);
xenbus_switch_state(dev, XenbusStateClosed);
wait_event(module_unload_q,
--
2.14.3
On 02/28/2018 07:23 AM, Jason Andryuk wrote:
> A toolstack may delete the vif frontend and backend xenstore entries
> while xen-netfront is in the removal code path. In that case, the
> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
> xennet_remove would hang indefinitely. This hang prevents system
> shutdown.
>
> xennet_remove must be able to handle XenbusStateUnknown, and
> netback_changed must also wake up the wake_queue for that state as well.
>
> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>
> Signed-off-by: Jason Andryuk <[email protected]>
> Cc: Eduardo Otubo <[email protected]>
Reviewed-by: Boris Ostrovsky <[email protected]>
On 28/02/18 13:23, Jason Andryuk wrote:
> A toolstack may delete the vif frontend and backend xenstore entries
> while xen-netfront is in the removal code path. In that case, the
> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
> xennet_remove would hang indefinitely. This hang prevents system
> shutdown.
>
> xennet_remove must be able to handle XenbusStateUnknown, and
> netback_changed must also wake up the wake_queue for that state as well.
>
> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>
> Signed-off-by: Jason Andryuk <[email protected]>
> Cc: Eduardo Otubo <[email protected]>
Committed to xen/tip for-linus-4.16a
Juergen
Jason Andryuk:
> A toolstack may delete the vif frontend and backend xenstore entries
> while xen-netfront is in the removal code path. In that case, the
> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
> xennet_remove would hang indefinitely. This hang prevents system
> shutdown.
>
> xennet_remove must be able to handle XenbusStateUnknown, and
> netback_changed must also wake up the wake_queue for that state as well.
>
> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
I think this should go into stable since AFAIK the hanging network
device can only be fixed by rebooting the guest. AFAICS this affects all
4.* branches since 5b5971df3bc2 got backported to them.
Upstream commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61.
Simon
On Thu, Apr 19, 2018 at 2:10 PM, Simon Gaiser
<[email protected]> wrote:
> Jason Andryuk:
>> A toolstack may delete the vif frontend and backend xenstore entries
>> while xen-netfront is in the removal code path. In that case, the
>> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
>> xennet_remove would hang indefinitely. This hang prevents system
>> shutdown.
>>
>> xennet_remove must be able to handle XenbusStateUnknown, and
>> netback_changed must also wake up the wake_queue for that state as well.
>>
>> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>
> I think this should go into stable since AFAIK the hanging network
> device can only be fixed by rebooting the guest. AFAICS this affects all
> 4.* branches since 5b5971df3bc2 got backported to them.
>
> Upstream commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61.
Simon,
Yes, I agree. I actually submitted the request to stable earlier
today, so hopefully it gets added soon.
Have you experienced this hang?
Regards,
Jason
Jason Andryuk:
> On Thu, Apr 19, 2018 at 2:10 PM, Simon Gaiser
> <[email protected]> wrote:
>> Jason Andryuk:
>>> A toolstack may delete the vif frontend and backend xenstore entries
>>> while xen-netfront is in the removal code path. In that case, the
>>> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
>>> xennet_remove would hang indefinitely. This hang prevents system
>>> shutdown.
>>>
>>> xennet_remove must be able to handle XenbusStateUnknown, and
>>> netback_changed must also wake up the wake_queue for that state as well.
>>>
>>> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>>
>> I think this should go into stable since AFAIK the hanging network
>> device can only be fixed by rebooting the guest. AFAICS this affects all
>> 4.* branches since 5b5971df3bc2 got backported to them.
>>
>> Upstream commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61.
>
> Simon,
>
> Yes, I agree. I actually submitted the request to stable earlier
> today, so hopefully it gets added soon.
Ok, great. (I checked the stable patch queue, but didn't check the
mailing list archive).
> Have you experienced this hang?
Yes, it's affecting the kernel shipped by Qubes OS (see [1]).
Thanks, Simon.
[1]: https://github.com/QubesOS/qubes-issues/issues/3657
On Thu, Apr 19, 2018 at 4:09 PM, Simon Gaiser
<[email protected]> wrote:
> Jason Andryuk:
>> On Thu, Apr 19, 2018 at 2:10 PM, Simon Gaiser
>> <[email protected]> wrote:
>>> Jason Andryuk:
>>>> A toolstack may delete the vif frontend and backend xenstore entries
>>>> while xen-netfront is in the removal code path. In that case, the
>>>> checks for xenbus_read_driver_state would return XenbusStateUnknown, and
>>>> xennet_remove would hang indefinitely. This hang prevents system
>>>> shutdown.
>>>>
>>>> xennet_remove must be able to handle XenbusStateUnknown, and
>>>> netback_changed must also wake up the wake_queue for that state as well.
>>>>
>>>> Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")
>>>
>>> I think this should go into stable since AFAIK the hanging network
>>> device can only be fixed by rebooting the guest. AFAICS this affects all
>>> 4.* branches since 5b5971df3bc2 got backported to them.
>>>
>>> Upstream commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61.
>>
>> Simon,
>>
>> Yes, I agree. I actually submitted the request to stable earlier
>> today, so hopefully it gets added soon.
>
> Ok, great. (I checked the stable patch queue, but didn't check the
> mailing list archive).
>
>> Have you experienced this hang?
>
> Yes, it's affecting the kernel shipped by Qubes OS (see [1]).
Ok, interesting. I tracked down this bug with older xenvm tools, and
I didn't know if libxl tools were also affected.
Greg KH added the patch to the stable queue, so it's in the process.
Regards,
Jason