[Hyper-V] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

Bug #1454892 reported by Joshua R. Poulson
22
This bug affects 3 people
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Won't Fix
High
Joseph Salisbury
Trusty
Won't Fix
High
Joseph Salisbury
Vivid
Fix Released
High
Joseph Salisbury
Wily
Fix Released
High
Joseph Salisbury
linux-lts-trusty (Ubuntu)
Won't Fix
High
Joseph Salisbury
Precise
Won't Fix
High
Joseph Salisbury
linux-lts-utopic (Ubuntu)
Won't Fix
High
Joseph Salisbury
Trusty
Won't Fix
High
Joseph Salisbury

Bug Description

hv_netvsc: Use the xmit_more skb flag to optimize signaling the host
Based on the information given to this driver (via the xmit_more skb flag),
we can defer signaling the host if more packets are on the way. This will help
make the host more efficient since it can potentially process a larger batch of
packets. Implement this optimization.

Upstream commit: https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=82fa3c776e5abba7ed6e4b4f4983d14731c37d6a

This commit may imply other commits previously requested, for example https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1452074

Requested for all typical Hyper-V targets: 15.10, 15.04, 14.10, 14.04, 14.04 HWE, 12.02, and 12.02 HWE

Revision history for this message
Brad Figg (brad-figg) wrote : Missing required logs.

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1454892

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu):
status: New → Incomplete
Revision history for this message
Joshua R. Poulson (jrp) wrote :

Upstream commit request, no logs required.

Changed in linux (Ubuntu):
status: Incomplete → Confirmed
tags: added: kernel-da-key kernel-hyper-v
Changed in linux (Ubuntu):
importance: Undecided → Medium
Changed in linux (Ubuntu Vivid):
status: New → Confirmed
Changed in linux (Ubuntu Utopic):
status: New → Triaged
Changed in linux (Ubuntu Vivid):
status: Confirmed → Triaged
Changed in linux (Ubuntu Wily):
status: Confirmed → Triaged
Changed in linux (Ubuntu Trusty):
status: New → Triaged
Changed in linux (Ubuntu Precise):
status: New → Triaged
Changed in linux (Ubuntu Vivid):
importance: Undecided → Medium
Changed in linux (Ubuntu Utopic):
importance: Undecided → Medium
Changed in linux (Ubuntu Trusty):
importance: Undecided → Medium
Changed in linux (Ubuntu Precise):
importance: Undecided → Medium
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I built a Vivid test kernel with the requested commit. There were some pre-req commits that were needed as well. The test kernel has the following commits applied:

4c0d9e0 hv_netvsc: Use the xmit_more skb flag to optimize signaling the host
2e16490 Drivers: hv: vmbus: Export the vmbus_sendpacket_pagebuffer_ctl()
b30dd3a Drivers: hv: vmbus: Suport an API to send pagebuffers with additional control
f93ca43 Drivers: hv: vmbus: Suport an API to send packet with additional control
068352e hv_netvsc: Fix a bug in netvsc_start_xmit()
be93771 hv_netvsc: Implement partial copy into send buffer
888ec2b hv_netvsc: Fix the packet free when it is in skb headroom
a0d749b hv_netvsc: Eliminate memory allocation in the packet send path
ef9700b hv_netvsc: Cleanup the test for freeing skb when we use sendbuf mechanism
929b8e8 hv_netvsc: Implement batching in send buffer

The Vivid test kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1454892/

Can you test this kernel and see if it resolves the bug? If it does, I'll build test kernels for all the other supported releases as well.

Thanks in advance!

Revision history for this message
Chris Valean (cvalean) wrote :

Joseph, can you please rebase these patches against the latest kernel for Vivid - 3.19.0-20 and let us know the kernel test path to re-test.
Multiple changes have been implemented since the -17/-18 releases.
Thank you!

Changed in linux (Ubuntu Precise):
status: Triaged → In Progress
Changed in linux (Ubuntu Trusty):
status: Triaged → In Progress
Changed in linux (Ubuntu Utopic):
status: Triaged → In Progress
Changed in linux (Ubuntu Vivid):
status: Triaged → In Progress
Changed in linux (Ubuntu Wily):
status: Triaged → In Progress
Changed in linux (Ubuntu Precise):
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Trusty):
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Utopic):
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Vivid):
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Wily):
assignee: nobody → Joseph Salisbury (jsalisbury)
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I built a new test kernel, which was rebased to 3.19.0-20. The test kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1454892

Revision history for this message
Chris Valean (cvalean) wrote :

Hi Joseph,
We're going to test the new kernel and update the thread in the next few days.
Thank you!

Revision history for this message
Joshua R. Poulson (jrp) wrote :

This kernel looks good.

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I created a Utopic test kernel with a backport of all the requested commits and their prereqs. The test kernel also has the commits from bug 1452074

The test kernel can be downloaded from:

http://kernel.ubuntu.com/~jsalisbury/lp1454892/utopic/

Changed in linux (Ubuntu Precise):
importance: Medium → High
Changed in linux (Ubuntu Trusty):
importance: Medium → High
Changed in linux (Ubuntu Utopic):
importance: Medium → High
Changed in linux (Ubuntu Vivid):
importance: Medium → High
Changed in linux (Ubuntu Wily):
importance: Medium → High
status: In Progress → Fix Released
Changed in linux (Ubuntu Trusty):
status: In Progress → Confirmed
Changed in linux (Ubuntu Precise):
status: In Progress → Confirmed
Brad Figg (brad-figg)
Changed in linux (Ubuntu Vivid):
status: In Progress → Fix Committed
Revision history for this message
nmeier (nmeier) wrote :

Installed the test kernel from comment #8 on a 14.10 server VM. Everything looks good. IPerf3 ran with no issues. The two Hyper-V hosts used for the test only had 1GB NICs, so iperf reported 920MB throughput.

Brad Figg (brad-figg)
Changed in linux (Ubuntu Utopic):
status: In Progress → Fix Committed
no longer affects: linux-lts-utopic (Ubuntu Precise)
no longer affects: linux-lts-utopic (Ubuntu Utopic)
no longer affects: linux-lts-utopic (Ubuntu Vivid)
no longer affects: linux-lts-utopic (Ubuntu Wily)
Changed in linux-lts-utopic (Ubuntu Trusty):
status: New → Fix Committed
Revision history for this message
Joshua R. Poulson (jrp) wrote :

Not sure why "no longer effects" has been placed here, we've acked the latest test kernel and are looking forward to this fix going out.

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I think that is just showing temporary changes where in linux-lts-utopic was marked as affecting Precise, Utopic, Vivid and Wily. However, there is no lts utopic kernel for those releases, there is only one for trusty, and that was was marked as "Fix Commited". So the fix is still coming as expected.

Changed in linux-lts-utopic (Ubuntu):
status: New → Fix Committed
importance: Undecided → High
Changed in linux-lts-utopic (Ubuntu Trusty):
importance: Undecided → High
Revision history for this message
Luis Henriques (henrix) wrote :

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-vivid' to 'verification-done-vivid'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

tags: added: verification-needed-vivid
Brad Figg (brad-figg)
tags: added: verification-needed-trusty
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

@nmeier or @jrp

Can you verify the -proposed kernel requested in comment #12?

Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package linux-lts-utopic - 3.16.0-48.64~14.04.1

---------------
linux-lts-utopic (3.16.0-48.64~14.04.1) trusty; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1487225

  [ Upstream Kernel Changes ]

  * sysfs: Create mountpoints with sysfs_create_mount_point
    - LP: #1487125

linux-lts-utopic (3.16.0-47.63~14.04.1) trusty; urgency=low

  [ Brad Figg ]

  * Release Tracking Bug
    - LP: #1485127

  [ Brad Figg ]

  * CONFIG: CONFIG_DELL_RBTN=m

  [ Upstream Kernel Changes ]

  * dell-rbtn: Dell Airplane Mode Switch driver
    - LP: #1440949
  * dell-rbtn: Export notifier for other kernel modules
  * dell-laptop: Use dell-rbtn instead i8042 filter when possible
  * net: Remove ndo_xmit_flush netdev operation, use signalling instead.
    - LP: #1454892
  * hyperv: Increase the buffer length for netvsc_channel_cb()
    - LP: #1454892
  * hyperv: Add support for vNIC hot removal
    - LP: #1454892
  * hyperv: fix sparse warnings
    - LP: #1454892
  * hv_netvsc: Implement batching in send buffer
    - LP: #1454892
  * hv_netvsc: Cleanup the test for freeing skb when we use sendbuf
    mechanism
    - LP: #1454892
  * hv_netvsc: Eliminate memory allocation in the packet send path
    - LP: #1454892
  * hv_netvsc: Fix the packet free when it is in skb headroom
    - LP: #1454892
  * hv_netvsc: Implement partial copy into send buffer
    - LP: #1454892
  * hv_netvsc: Fix a bug in netvsc_start_xmit()
    - LP: #1454892
  * Drivers: hv: vmbus: Suport an API to send packet with additional
    control
    - LP: #1454892
  * Drivers: hv: vmbus: Suport an API to send pagebuffers with additional
    control
    - LP: #1454892
  * Drivers: hv: vmbus: Export the vmbus_sendpacket_pagebuffer_ctl()
    - LP: #1454892
  * hv_netvsc: Use the xmit_more skb flag to optimize signaling the host
    - LP: #1454892

 -- Luis Henriques <email address hidden> Thu, 20 Aug 2015 23:10:28 +0100

Changed in linux-lts-utopic (Ubuntu Trusty):
status: Fix Committed → Fix Released
status: Fix Committed → Fix Released
Revision history for this message
Launchpad Janitor (janitor) wrote :
Download full text (14.6 KiB)

This bug was fixed in the package linux - 3.19.0-28.30

---------------
linux (3.19.0-28.30) vivid; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1490606

  [ Gary Wang ]

  * SAUCE: i915_bpo: drm/i915: set CDCLK if DPLL0 enabled during resuming
    from S3
    - LP: #1490035

  [ Timo Aaltonen ]

  * Revert "SAUCE: i915_bpo: drm/i915/skl: DDI-E and DDI-A shares 4 lanes."
    - LP: #1490038

linux (3.19.0-27.29) vivid; urgency=low

  [ Brad Figg ]

  * Release Tracking Bug
    - LP: #1485113

  [ Adam Lee ]

  * SAUCE: serial: 8250_pci: Add support for Pericom PI7C9X795[1248]
    - LP: #1480142

  [ Arun Siluvery ]

  * SAUCE: i915_bpo: drm/i915/gen8: Add infrastructure to initialize WA
    batch buffers
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen8: Re-order init pipe_control in lrc mode
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen8: Add WaDisableCtxRestoreArbitration
    workaround
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen8: Add
    WaFlushCoherentL3CacheLinesAtContextSwitch workaround
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915: Bail out early if WA batch is not available
    for given Gen
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen8: Add WaClearSlmSpaceAtContextSwitch
    workaround
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915: Update
    WaFlushCoherentL3CacheLinesAtContextSwitch
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915: Enable WA batch buffers for Gen9
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen9: Add WaDisableCtxRestoreArbitration
    workaround
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915: Update wa_ctx_emit() macro as per kernel
    coding guidelines
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen9: Add
    WaFlushCoherentL3CacheLinesAtContextSwitch workaround
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915/gen9: Add
    WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915:skl: Add WaEnableGapsTsvCreditFix
    - LP: #1484486

  [ Chris Wilson ]

  * SAUCE: i915_bpo: drm/i915: Use two 32bit reads for select 64bit
    REG_READ ioctls
    - LP: #1484482
  * SAUCE: i915_bpo: drm/i915: Replace WARN inside I915_READ64_2x32 with
    retry loop
    - LP: #1484482
  * SAUCE: i915_bpo: drm/i915: Mark PIN_USER binding as GLOBAL_BIND without
    the aliasing ppgtt
    - LP: #1484482
  * SAUCE: i915_bpo: drm/i915: Declare the swizzling unknown for L-shaped
    configurations
    - LP: #1484482

  [ Damien Lespiau ]

  * SAUCE: i915_bpo: drm/i915/skl: Don't expose the top most plane on gen9
    display
    - LP: #1484486

  [ Daniel Vetter ]

  * SAUCE: i915_bpo: drm/i915: Fixup dp mst encoder selection
    - LP: #1484482

  [ David Weinehall ]

  * SAUCE: i915_bpo: drm/i915: Allow parsing of variable size child device
    entries from VBT
  * SAUCE: i915_bpo: drm/i915: Allow parsing of variable size child device
    entries from VBT, addendum v2
    - LP: #1484482

  [ Jani Nikula ]

  * SAUCE: i915_bpo: drm/i915/skl: WaIgnoreDDIAStrap is forever, always
    init DDI A
    - LP: #1484486
  * SAUCE: i915_bpo: drm/i915: reduce indent in i9xx_hpd_irq_handler
    - LP: #1484531
  * SAUCE: i915_bpo: drm/i91...

Changed in linux (Ubuntu Vivid):
status: Fix Committed → Fix Released
status: Fix Committed → Fix Released
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

Possible regression in lts-backport-utpic due to backport of commit 0b725a2c. See bug 1492146 .

Revision history for this message
Luis Henriques (henrix) wrote :

Due to the regression referred to in comment #18 we are reverting this patchset from linux-lts-utopic.

Luis Henriques (henrix)
Changed in linux-lts-utopic (Ubuntu Trusty):
status: Fix Released → Triaged
Changed in linux-lts-utopic (Ubuntu):
status: Fix Committed → Triaged
Changed in linux (Ubuntu Utopic):
status: Fix Committed → Invalid
assignee: Joseph Salisbury (jsalisbury) → nobody
Changed in linux-lts-utopic (Ubuntu):
status: Triaged → In Progress
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Trusty):
status: Confirmed → In Progress
no longer affects: linux (Ubuntu Precise)
no longer affects: linux (Ubuntu Utopic)
Changed in linux-lts-utopic (Ubuntu Trusty):
status: Triaged → In Progress
assignee: nobody → Joseph Salisbury (jsalisbury)
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

As mentioned in comment #18, the fixes for this bug caused a regression in linux-lts-utopic. I created a new linux-lts-utopic test kernel with all the patches for this bug, plus two additional prereqs that were needed to prevent the regression from happening again.

I asked for testing of this new test kernel in bug 1492146. Once we can confirm the fixes don't cause the regression again, they can be SRU'd.

Revision history for this message
Joshua R. Poulson (jrp) wrote :

I am also concerned about bug 1521053

Changed in linux (Ubuntu):
status: Fix Released → In Progress
Revision history for this message
Joshua R. Poulson (jrp) wrote :

Consider the following upstream commit and its prerequisites with respect to some people having trouble with the SRB flag:
storvsc_drv.c : commit 8cf308e1225f5f93575f03cc4dbef24516fa81c9 : storvsc: Don't set the SRB_FLAGS_QUEUE_ACTION_ENABLE flag

I'm wondering if it affected more than just the qlogic device with which we had difficulty. We don't have the device in question to test with.

Revision history for this message
Joshua R. Poulson (jrp) wrote :

My paste missed

storvsc_drv.c : commit 3209f9d780d137cdb54c85e0a776cb19e723a170 : scsi: storvsc: Fix a bug in the handling of SRB status flags

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

One of the prerequisite commits required for this patch to apply to lts-backport-utopic and Trusty(Commit 0b725a2c) was making changes to the igb driver.

I created a new backport of this commit, so it does not touch igb. There was good testing in bug 1492146 with this kernel, see commits 34 -> 37.

Can you also test this linux-lts-utopic kernel to see if it resolves this bug? If it does, I'll build a Trusty test kernel for testing. We can then re-submit the SRU request the fixes will no longer cause the regression.

The linux-lts-utopic kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1454892/lts-backport-utopic/

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

If we can receive positive test feedback by January 8th, we can proceed to submit the patches for kernel SRU review in an attempt to make the upcoming kernel SRU cycle starting on January 10th. Assuming the patches are accepted for SRU and land in the upcoming SRU cycle, the fix should be available from the -updates pocket by January 30th.

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

Hi Josh,

Do you happen to know if testing was performed with the test kernel as of yet? Some of the Trusty prereqs for bug 1519897 would come in via this bug fix.

Revision history for this message
Joshua R. Poulson (jrp) wrote :

Sorry, the test team was buried under some other items, and we had not made it to this one yet.

Revision history for this message
Chris Valean (cvalean) wrote :

Hi Joe,
We've attempted to validate the linux-lts-utopic test kernel provided, however on a Trusty system the VM is not stable in terms of getting the network connectivity, as during performance testing, the system tend to loose the test interface connection.

Can you please confirm if commit 8599846d73 is checked in?
http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=8599846d73997cdbccf63f23394d871cfad1e5e6

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

Hi Chris,

The linux-lts-utopic test kernel did not have that commit applied since it is being addressed in bug 1519897.

It sounds like these two bugs should be tied togeter. What do you think? I can rebuild the test kernel with all the commits for this bug and with commit 8599846d7.

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I build one more test kernel, but it also includes commits 8599846d and 5f5cc8173. The new v2 test kernel can be downloaded from:

http://kernel.ubuntu.com/~jsalisbury/lp1454892/lts-backport-utopic/

Can you test this kernel and see if it resolves this bug?

Revision history for this message
Joshua R. Poulson (jrp) wrote :

Is this test kernel utopic or trusty? We are expecting 12.04.5 fixes to go into lts-trusty (HWE).

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

The test kernel in comment #30 is for the utopic HWE kernel in trusty. I'll also build a Trusty HWE kernel for Precise and post it shortly.

Changed in linux-lts-trusty (Ubuntu Trusty):
status: New → In Progress
Changed in linux-lts-trusty (Ubuntu):
status: New → In Progress
importance: Undecided → High
assignee: nobody → Joseph Salisbury (jsalisbury)
Changed in linux-lts-trusty (Ubuntu Trusty):
assignee: nobody → Joseph Salisbury (jsalisbury)
importance: Undecided → High
no longer affects: linux-lts-trusty (Ubuntu Trusty)
no longer affects: linux (Ubuntu Precise)
Changed in linux-lts-trusty (Ubuntu Precise):
status: New → In Progress
importance: Undecided → High
assignee: nobody → Joseph Salisbury (jsalisbury)
no longer affects: linux-lts-utopic (Ubuntu Precise)
Revision history for this message
Joshua R. Poulson (jrp) wrote :

Ah, I thought the 3.16 kernel was no longer updated except CVEs as utopic was only used for 14.04.2 and that was deprecated to vivid for 14.04.3. In my documentation I encourage users on 12.04 to run lts-trusty, 14.04 to run lts-vivid, and in some cases I even advise some customers to move to lts-wily on 14.04.

Revision history for this message
Chris Valean (cvalean) wrote :

Hi Joe,
I verified the v2 test kernel from comment #30 and the network performance tests have passed successfully now.
The network connection didn't drop between the systems, please proceed with merging these changes.

Changed in linux-lts-utopic (Ubuntu):
status: In Progress → Won't Fix
Changed in linux-lts-utopic (Ubuntu Trusty):
status: In Progress → Won't Fix
Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

I built a Trusty test kernel. Sorry for the delay, it required backporting 20 other commits.

The test kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1454892/trusty/

Can you test this kernel and see if it resolves this bug?

Thanks in advance!

Revision history for this message
Chris Valean (cvalean) wrote :

This lts-trusty test kernel is not booting when installed on 12.04.5.

There are multiple events like this being recorded on the serial:
udevd[275]: timeout: killing '/sbin/modprobe -bv vmbus:394f16571591784eab55382f3bd5422d' [380]
udevd[246]: timeout: killing '/sbin/modprobe -bv vmbus:e7f4a0a9455a964db8278a841e8c03e6' [386]
udevd[249]: timeout: killing '/sbin/modprobe -bv vmbus:292efa3523ea364296ae3a6ebacba440' [394]

Removing the network card from the VM config, the system is booting normally.
Trying to boot the VM again with a NIC attached, the system is booting eventually, though we see the failed modprobe attempts.

There is also this call trace showing up that I was able to capture. Will check with the peers from our end if we can identify the missing patch or the one that's causing this.

[ 361.072113] INFO: task modprobe:740 blocked for more than 120 seconds.
[ 361.074061] Not tainted 3.13.0-78-generic #122
[ 361.075771] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 361.077886] modprobe D ffff88007ce33180 0 740 656 0x00000004
[ 361.077896] ffff880078193bc0 0000000000000086 ffff880036b26000 0000000000013180
[ 361.077901] ffff880078193fd8 0000000000013180 ffff880036b26000 ffff88007b60c240
[ 361.077905] ffff88007b60c244 ffff880036b26000 00000000ffffffff ffff88007b60c248
[ 361.077916] Call Trace:
[ 361.077924] [<ffffffff817294c9>] schedule_preempt_disabled+0x29/0x70
[ 361.077930] [<ffffffff8172b335>] __mutex_lock_slowpath+0x135/0x1b0
[ 361.077938] [<ffffffff81499e50>] ? __device_attach+0x40/0x40
[ 361.077943] [<ffffffff8172b3cf>] mutex_lock+0x1f/0x2f
[ 361.077953] [<ffffffff81499e99>] __driver_attach+0x49/0xa0
[ 361.077958] [<ffffffff81499e50>] ? __device_attach+0x40/0x40
[ 361.077963] [<ffffffff81497aa3>] bus_for_each_dev+0x63/0xa0
[ 361.077970] [<ffffffff8149950e>] driver_attach+0x1e/0x20
[ 361.077975] [<ffffffff814990f0>] bus_add_driver+0x180/0x250
[ 361.077986] [<ffffffff8149a564>] driver_register+0x64/0xf0
[ 361.077996] [<ffffffffa001bda7>] __vmbus_driver_register+0x57/0x60 [hv_vmbus]
[ 361.078001] [<ffffffffa0049000>] ? 0xffffffffa0048fff
[ 361.078009] [<ffffffffa004901e>] hv_kbd_init+0x1e/0x1000 [hyperv_keyboard]
[ 361.078019] [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
[ 361.078026] [<ffffffff81059833>] ? set_memory_nx+0x43/0x50
[ 361.078032] [<ffffffff810e28fd>] load_module+0x12ed/0x1b50
[ 361.078038] [<ffffffff810de350>] ? store_uevent+0x40/0x40
[ 361.078049] [<ffffffff810e3202>] SyS_init_module+0xa2/0xf0
[ 361.078054] [<ffffffff817356dd>] system_call_fastpath+0x1a/0x1f

Changed in linux-lts-trusty (Ubuntu Precise):
status: In Progress → Won't Fix
Changed in linux-lts-trusty (Ubuntu):
status: In Progress → Won't Fix
Changed in linux (Ubuntu Trusty):
status: In Progress → Won't Fix
Changed in linux (Ubuntu):
status: In Progress → Won't Fix
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