On Wed, 20 Jun 2018 08:01:50 +0900
Greg KH <g...@kroah.com> wrote:
> On Tue, Jun 19, 2018 at 03:19:41PM -0400, Thomas Walker wrote:
> > Upon updating some internal kernels from 4.14.18 to 4.14.49, our hyper-v
> > guests failed to bring up network interfaces on boot, logging "A link
> > change request failed with some changes committed already. Interface eth0
> > may have been left with an inconsistent configuration, please check."
> > Running 'ifconfig eth0 up' appears to fix the problem temporarily so I went
> > about bisecting which landed on:
> >
> > commit be9c798d0d13ae609a91177323ac816545c39d28
> > Author: Stephen Hemminger <step...@networkplumber.org>
> > Date: Mon May 14 15:32:18 2018 -0700
> >
> > hv_netvsc: common detach logic
> >
> > [ Commit 7b2ee50c0cd513a176a26a71f2989facdd75bfea upstream. ]
> >
> > Make common function for detaching internals of device
> > during changes to MTU and RSS. Make sure no more packets
> > are transmitted and all packets have been received before
> > doing device teardown.
> >
> > Change the wait logic to be common and use usleep_range().
> >
> > Changes transmit enabling logic so that transmit queues are disabled
> > during the period when lower device is being changed. And enabled
> > only after sub channels are setup. This avoids issue where it could
> > be that a packet was being sent while subchannel was not initialized.
> >
> > Fixes: 8195b1396ec8 ("hv_netvsc: fix deadlock on hotplug")
> > Signed-off-by: Stephen Hemminger <sthem...@microsoft.com>
> > Signed-off-by: David S. Miller <da...@davemloft.net>
> > Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> >
> >
> > The removal of which does indeed fix the problem. That led me to:
> >
> > commit 52acf73b6e9a6962045feb2ba5a8921da2201915
> > Author: Dexuan Cui <de...@microsoft.com>
> > Date: Wed Jun 6 21:32:51 2018 +0000
> >
> > hv_netvsc: Fix a network regression after ifdown/ifup
> >
> > Recently people reported the NIC stops working after
> > "ifdown eth0; ifup eth0". It turns out in this case the TX queues are
> > not
> > enabled, after the refactoring of the common detach logic: when the NIC
> > has sub-channels, usually we enable all the TX queues after all
> > sub-channels are set up: see rndis_set_subchannel() ->
> > netif_device_attach(), but in the case of "ifdown eth0; ifup eth0" where
> > the number of channels doesn't change, we also must make sure the TX
> > queues
> > are enabled. The patch fixes the regression.
> >
> > Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
> > Signed-off-by: Dexuan Cui <de...@microsoft.com>
> > Cc: Stephen Hemminger <sthem...@microsoft.com>
> > Cc: K. Y. Srinivasan <k...@microsoft.com>
> > Cc: Haiyang Zhang <haiya...@microsoft.com>
> > Signed-off-by: David S. Miller <da...@davemloft.net>
> >
> > Which sounded very promising, but does not seem to fully fix the issue.
> > Doing some more digging, I was able to determine that the message coincides
> > with 'ip link set dev eth0 mtu 1300 up' very shortly (>~1 second) after the
> > hv_netvsc driver loads. If I delay the mtu change until well after the
> > driver loads, everything works fine. If I unload hv_netvsc and then reload
> > it and apply the mtu change immediately, the failure re-occurs. So
> > something is racy here, and the above doesn't entirely address it.
> >
> > I'm happy to test out any suggested patches and/or do additional debugging
> > if anyone has any suggestions.
> >
> > (oh, and I did also try 4.18-rc1 and the problem still persists)
>
> Always cc: the authors of the patch you are having problems with, along
> with the mailing list for the networking subsystem, so that the right
> people know to look at this.
Let me take a look at it, and log it into the bug system.
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