mono occassionally crashes since kernel 3.13.0-48 on multi-cpu vm

[Taloth Saldono]

[Impact]
The addition of the commit:
http://kernel.ubuntu.com/git/ubuntu/ubuntu-trusty.git/commit/?id=11f4e0339c8dc8d760483258efd9f15b4c6dcda2

Causes SIGSEGVs when running certain workloads on multi-cpu VMs.

[Test Case]

Mono test case here that causes the SIGSEGV
https://bugzilla.xamarin.com/show_bug.cgi?id=29212

[Fix]

These two commits are required for fixing this issue:
https://github.com/torvalds/linux/commit/80f7fdb1c7f0f9266421f823964fd1962681f6ce
https://github.com/torvalds/linux/commit/0a4e6be9ca17c54817cf814b4b5aa60478c6df27

--

Gradually since late March more and more users started to complain about frequent SIGSEGV crashes in our .net/mono application. Early April I started to investigate it actively.

After eliminating possible native libraries, and testing various mono versions I discovered the crashes would occur more frequently on a vbox vm with multiple cpus configured. And discovered that the mono bug-18026.cs testcase would fairly consistently crash. At that point it was reported to the mono bug tracker.

I finally got a break when we found a correlation with the kernel version. 3.13.0-46 didn't crash while 3.13.0-48,49 did.
More and more users upgrade to these newer kernel versions and start running into issues, which explains the gradual increase in reports.

Early this week I performed a full git bisect on the kernel between 3.13.0-46 and -48 and isolated the commit that seems to trigger the crashes.
Namely http://kernel.ubuntu.com/git/ubuntu/ubuntu-trusty.git/commit/?id=11f4e0339c8dc8d760483258efd9f15b4c6dcda2

At this point I don't know if the commit messed up something, or that mono simply handles it incorrectly. However, a few commits for linux 4.x seem to fix it:
https://github.com/torvalds/linux/commit/80f7fdb1c7f0f9266421f823964fd1962681f6ce
https://github.com/torvalds/linux/commit/0a4e6be9ca17c54817cf814b4b5aa60478c6df27
I applied these commits myself on top of commit 11f4e033, compiled and ran the testcase... didn't crash in the 200x test runs I did.
Although I don't know if those two patches have unknown side-effects.
I'm not an expert on the kernel, not even remotely. But I thought it would be nice to be able to point at a possible solution.

My current test vm is a virtualbox vm 64bit installed using the 14.04.2 server iso running on an older i7 quad core Windows 7 64bit host.
In the vm I've tested numerous mono and kernel combinations. Last test was with kernel 3.16.0-36 and 3.13.0-51 and mono 4.0.1, in which the problem still occurs.

By now I've debugged the app using gdb several dozen times on various user setups, compiled mono half a dozen times, and then the 8x3h compile kernel bisect :) Speaking of down the rabbit-hole...

So I'm pretty desperate for some expert to help me out here. :D

Reference to mono bug report: https://bugzilla.xamarin.com/show_bug.cgi?id=29212

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-51-generic 3.13.0-51.84
ProcVersionSignature: Ubuntu 3.13.0-51.84-generic 3.13.11-ckt18
Uname: Linux 3.13.0-51-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Apr 30 18:53 seq
 crw-rw---- 1 root audio 116, 33 Apr 30 18:53 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.14.1-0ubuntu3.10
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: Error: [Errno 2] No such file or directory: 'iw'
CurrentDmesg: [ 9.379188] init: plymouth-upstart-bridge main process ended, respawning
Date: Thu Apr 30 19:45:43 2015
HibernationDevice: RESUME=UUID=b35ef328-166d-4476-a418-e7e80d22cb30
InstallationDate: Installed on 2015-04-22 (7 days ago)
InstallationMedia: Ubuntu-Server 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
IwConfig:
 eth0 no wireless extensions.

 lo no wireless extensions.
Lsusb:
 Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: innotek GmbH VirtualBox
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-51-generic root=UUID=68da7e09-1a91-4107-859d-bf452f9ed992 ro
RelatedPackageVersions:
 linux-restricted-modules-3.13.0-51-generic N/A
 linux-backports-modules-3.13.0-51-generic N/A
 linux-firmware 1.127.11
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH

[Brad Figg (brad-figg)]

This change was made by a bot.

[Badr CHOUFFAI (chouffainet)]

The fix is not available and not working. I confirm that the bug of stills crashing Mono every 5 minutes. Incredible !

[Christopher M. Penalver (penalvch)]

Badr CHOUFFAI, if the fix is not available, not working, and you confirm the crash still, how is this Fix Released as defined in https://wiki.ubuntu.com/Bugs/Status ?

[Taloth Saldono (talothsaldono)]

I tested the patches earlier, so it should be good.
But just for the record:
I just pulled the trusty master-next branch, built and tested on the test vm.
The crash doesn't occur for me anymore in the reported scenario.

Atm, it looks like the fix will be in 3.13.0-54 but afaik we have to wait for 53 to be cleared out of proposed first.
The fix also seems to be in the upstream linux SRUs (or whatever it's called) so other distros will likely get it as well.

Once -54 makes it to proposed I'll get some of our users to try it out, see if that was the only issue causing those crashes. But I'm optimistic.

(Btw. on -53 it still crashes instantly, as expected)

[Badr CHOUFFAI (chouffainet)]

On my website www.medinet.fr, I am using Ubuntu Server and Mono. I downgraded the serverto one CPU for having no crashes and waiting for the right fix. The said fixed one does not work at all. The server crashes eash 10 minutes max. Regards. M. Badr CHOUFFAI. .Net Software Architect.

[BrandonG777 (brandongabbard)]

This bug is still affecting me on 3.13.0-53-generic

[Taloth Saldono (talothsaldono)]

As mentioned in my last comment, you'll have to wait for -54.

[Taloth Saldono (talothsaldono)]

I had a couple of users test 3.13.0-54 and 3.16.0-39 proposed.
After more than 24h they haven't experienced a crash whereas before it would likely crash between minutes to an hour.

Please note we also now confirmed earlier suspicions that the issue didn't only happen on VMs but also physical systems.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.19.0-20.20

---------------
linux (3.19.0-20.20) vivid; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1459957
  * Revert "SAUCE: Call i915_bpo specific functions from the hda driver"
    - LP: #1457369

linux (3.19.0-19.19) vivid; urgency=low

  [ Brad Figg ]

  * Release Tracking Bug
    - LP: #1458964

  [ Duc Dang ]

  * SAUCE: (no-up) [PCIE] APM X-Gene: Remove debug messages in MSI
    interrupt handler path.
    - LP: #1451593

  [ Luis Henriques ]

  * [Config] updateconfigs for 3.19.7 stable update

  [ Paolo Pisati ]

  * [Config] armhf: CPUFREQ_DT=y
    - LP: #1457781
  * annotations: enforce CPUFREQ_DT
    - LP: #1457781

  [ Tanmay Inamdar ]

  * SAUCE: (no-up) Add MSI/MSI-X driver for APM PCI bus
    - LP: #1451593

  [ Timo Aaltonen ]

  * SAUCE: i915_bpo: Rebase to v4.1-rc4.
    - LP: #1456123
  * SAUCE: i915_bpo: Revert dma-buf: cleanup dma_buf_export() to make it
    easily extensible
    - LP: #1456123

  [ Tuan Phan ]

  * SAUCE: (no-up) pci-xgene-msi: fixed deadlock in irq_set_affinity
    - LP: #1451593

  [ Upstream Kernel Changes ]

  * Revert "nfs: replace nfs_add_stats with nfs_inc_stats when add one"
    - LP: #1454699
  * cpufreq: powernv: Report cpu frequency throttling
    - LP: #1452547
  * x86: kvm: Revert "remove sched notifier for cross-cpu migrations"
    - LP: #1450584
  * x86: vdso: fix pvclock races with task migration
    - LP: #1450584
  * ip_forward: Drop frames with attached skb->sk
    - LP: #1454699
  * net: add skb_checksum_complete_unset
    - LP: #1454699
  * ppp: call skb_checksum_complete_unset in ppp_receive_frame
    - LP: #1454699
  * tcp: fix possible deadlock in tcp_send_fin()
    - LP: #1454699
  * tcp: avoid looping in tcp_send_fin()
    - LP: #1454699
  * net: do not deplete pfmemalloc reserve
    - LP: #1454699
  * net: fix crash in build_skb()
    - LP: #1454699
  * pxa168: fix double deallocation of managed resources
    - LP: #1454699
  * net/mlx4_en: Prevent setting invalid RSS hash function
    - LP: #1454699
  * md: fix md io stats accounting broken
    - LP: #1454699
  * x86/asm/decoder: Fix and enforce max instruction size in the insn
    decoder
    - LP: #1454699
  * sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve
    power savings and to improve performance
    - LP: #1454699
  * sched/idle/x86: Optimize unnecessary mwait_idle() resched IPIs
    - LP: #1454699
  * perf/x86/intel: Fix Core2,Atom,NHM,WSM cycles:pp events
    - LP: #1454699
  * KVM: x86: Fix MSR_IA32_BNDCFGS in msrs_to_save
    - LP: #1454699
  * Btrfs: fix log tree corruption when fs mounted with -o discard
    - LP: #1454699
  * btrfs: don't accept bare namespace as a valid xattr
    - LP: #1454699
  * Btrfs: fix inode eviction infinite loop after cloning into it
    - LP: #1454699
  * Btrfs: fix inode eviction infinite loop after extent_same ioctl
    - LP: #1454699
  * usb: gadget: printer: enqueue printer's response for setup request
    - LP: #1454699
  * KVM: s390: fix handling of write errors in the tpi handler
    - LP: #1454699
  * KVM: s390: reinjection of irqs can fail in the tpi handler
    - LP: #1454699
  * KVM:...

[Luis Henriques (henrix)]

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-trusty' to 'verification-done-trusty'.

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!

[Luis Henriques (henrix)]

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-utopic' to 'verification-done-utopic'.

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!

[Luis Henriques (henrix)]

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!

[Taloth Saldono (talothsaldono)]

Verified on trusty and utopic, both by myself and several users.

But I haven't been able to reproduce it on an earlier linux-generic-lts-vivid release. Not sure if a different gcc version is used to compile vivid, preventing the bug from showing itself. (Considering the original commit)

I'll run the testcase for a longer time and report back later.

[Taloth Saldono (talothsaldono)]

I never looked into vivid before. So I didn't know whether the problem also occurred on vivid.

I've run the testcase for several hours now on the older 3.19.0-16, without crash.

But on vivid there's a lot more commits on vdso:
http://kernel.ubuntu.com/git/ubuntu/ubuntu-vivid.git/log/arch/x86/vdso/vclock_gettime.c
vs
http://kernel.ubuntu.com/git/ubuntu/ubuntu-trusty.git/log/arch/x86/vdso/vclock_gettime.c

I'm not sure if that affects reproducibility on vivid.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.19.0-20.20

---------------
linux (3.19.0-20.20) vivid; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1459957
  * Revert "SAUCE: Call i915_bpo specific functions from the hda driver"
    - LP: #1457369

linux (3.19.0-19.19) vivid; urgency=low

  [ Brad Figg ]

  * Release Tracking Bug
    - LP: #1458964

  [ Duc Dang ]

  * SAUCE: (no-up) [PCIE] APM X-Gene: Remove debug messages in MSI
    interrupt handler path.
    - LP: #1451593

  [ Luis Henriques ]

  * [Config] updateconfigs for 3.19.7 stable update

  [ Paolo Pisati ]

  * [Config] armhf: CPUFREQ_DT=y
    - LP: #1457781
  * annotations: enforce CPUFREQ_DT
    - LP: #1457781

  [ Tanmay Inamdar ]

  * SAUCE: (no-up) Add MSI/MSI-X driver for APM PCI bus
    - LP: #1451593

  [ Timo Aaltonen ]

  * SAUCE: i915_bpo: Rebase to v4.1-rc4.
    - LP: #1456123
  * SAUCE: i915_bpo: Revert dma-buf: cleanup dma_buf_export() to make it
    easily extensible
    - LP: #1456123

  [ Tuan Phan ]

  * SAUCE: (no-up) pci-xgene-msi: fixed deadlock in irq_set_affinity
    - LP: #1451593

  [ Upstream Kernel Changes ]

  * Revert "nfs: replace nfs_add_stats with nfs_inc_stats when add one"
    - LP: #1454699
  * cpufreq: powernv: Report cpu frequency throttling
    - LP: #1452547
  * x86: kvm: Revert "remove sched notifier for cross-cpu migrations"
    - LP: #1450584
  * x86: vdso: fix pvclock races with task migration
    - LP: #1450584
  * ip_forward: Drop frames with attached skb->sk
    - LP: #1454699
  * net: add skb_checksum_complete_unset
    - LP: #1454699
  * ppp: call skb_checksum_complete_unset in ppp_receive_frame
    - LP: #1454699
  * tcp: fix possible deadlock in tcp_send_fin()
    - LP: #1454699
  * tcp: avoid looping in tcp_send_fin()
    - LP: #1454699
  * net: do not deplete pfmemalloc reserve
    - LP: #1454699
  * net: fix crash in build_skb()
    - LP: #1454699
  * pxa168: fix double deallocation of managed resources
    - LP: #1454699
  * net/mlx4_en: Prevent setting invalid RSS hash function
    - LP: #1454699
  * md: fix md io stats accounting broken
    - LP: #1454699
  * x86/asm/decoder: Fix and enforce max instruction size in the insn
    decoder
    - LP: #1454699
  * sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve
    power savings and to improve performance
    - LP: #1454699
  * sched/idle/x86: Optimize unnecessary mwait_idle() resched IPIs
    - LP: #1454699
  * perf/x86/intel: Fix Core2,Atom,NHM,WSM cycles:pp events
    - LP: #1454699
  * KVM: x86: Fix MSR_IA32_BNDCFGS in msrs_to_save
    - LP: #1454699
  * Btrfs: fix log tree corruption when fs mounted with -o discard
    - LP: #1454699
  * btrfs: don't accept bare namespace as a valid xattr
    - LP: #1454699
  * Btrfs: fix inode eviction infinite loop after cloning into it
    - LP: #1454699
  * Btrfs: fix inode eviction infinite loop after extent_same ioctl
    - LP: #1454699
  * usb: gadget: printer: enqueue printer's response for setup request
    - LP: #1454699
  * KVM: s390: fix handling of write errors in the tpi handler
    - LP: #1454699
  * KVM: s390: reinjection of irqs can fail in the tpi handler
    - LP: #1454699
  * KVM:...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.16.0-39.53

---------------
linux (3.16.0-39.53) utopic; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1458778

  [ Brad Figg ]

  * hyper-v -- add hid and fb drivers to linux-virtual
    - LP: #1444179

  [ Chris J Arges ]

  * [Config] CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y on ppc64el
    - LP: #1450497

  [ Luis Henriques ]

  * SAUCE: (no-up) trace: fix trace_open_exec() invocation
    - LP: #1453848

  [ Paolo Pisati ]

  * [Config] armhf: GENERIC_CPUFREQ_CPU0=y
    - LP: #1457781

  [ Upstream Kernel Changes ]

  * DT doc: net: cpsw mac-address is optional
    - LP: #1452628
  * net: cpsw: Add missing return value
    - LP: #1452628
  * net: cpsw: header, Add missing include
    - LP: #1452628
  * net: cpsw: Replace pr_err by dev_err
    - LP: #1452628
  * net: cpsw: Add am33xx MACID readout
    - LP: #1452628
  * am33xx: define syscon control module device node
    - LP: #1452628
  * arm: dts: am33xx, Add syscon phandle to cpsw node
    - LP: #1452628
  * x86: kvm: Revert "remove sched notifier for cross-cpu migrations"
    - LP: #1450584
  * x86: vdso: fix pvclock races with task migration
    - LP: #1450584
  * n_tty: Fix read buffer overwrite when no newline
    - LP: #1454202
  * spi: spidev: fix possible arithmetic overflow for multi-transfer
    message
    - LP: #1454202
  * arm64: vdso: fix build error when switching from LE to BE
    - LP: #1454202
  * uas: Do not blacklist ASM1153 disk enclosures
    - LP: #1454202
  * KVM: x86: Fix lost interrupt on irr_pending race
    - LP: #1454202
  * tcp: prevent fetching dst twice in early demux code
    - LP: #1454202
  * ipv6: protect skb->sk accesses from recursive dereference inside the
    stack
    - LP: #1454202
  * tcp: tcp_make_synack() should clear skb->tstamp
    - LP: #1454202
  * usbnet: Fix tx_packets stat for FLAG_MULTI_FRAME drivers
    - LP: #1454202
  * usbnet: Fix tx_bytes statistic running backward in cdc_ncm
    - LP: #1454202
  * bonding: Bonding Overriding Configuration logic restored.
    - LP: #1454202
  * HID: add ALWAYS_POLL quirk for a Logitech 0xc007
    - LP: #1454202
  * PCI/AER: Avoid info leak in __print_tlp_header()
    - LP: #1454202
  * PCI: cpcihp: Add missing curly braces in cpci_configure_slot()
    - LP: #1454202
  * sh_veu: v4l2_dev wasn't set
    - LP: #1454202
  * media: s5p-mfc: fix mmap support for 64bit arch
    - LP: #1454202
  * cpufreq: Schedule work for the first-online CPU on resume
    - LP: #1454202
  * cpuidle: remove state_count field from struct cpuidle_device
    - LP: #1454202
  * cpuidle: ACPI: do not overwrite name and description of C0
    - LP: #1454202
  * ioctx_alloc(): fix vma (and file) leak on failure
    - LP: #1454202
  * drm/i915/vlv: save/restore the power context base reg
    - LP: #1454202
  * drm/i915/chv: Remove Wait for a previous gfx force-off
    - LP: #1454202
  * drm/i915/vlv: remove wait for previous GFX clk disable request
    - LP: #1454202
  * ALSA: hda/realtek - Make more stable to get pin sense for ALC283
    - LP: #1454202
  * ALSA: bebob: fix to processing in big-endian machine for sending cue
    - LP: #1454202
  * be2iscsi: Fix kern...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.13.0-54.91

---------------
linux (3.13.0-54.91) trusty; urgency=medium

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1458618

  [ Upstream Kernel Changes ]

  * [3.13-stable only] Revert "gianfar: Carefully free skbs in functions
    called by netpoll."
    - LP: #1454746

linux (3.13.0-54.90) trusty; urgency=low

  [ Luis Henriques ]

  * Release Tracking Bug
    - LP: #1458618

  [ Andy Whitcroft ]

  * [Config] push off linux-lts-{utopic, vivid}-tools-common
    - LP: #1405807

  [ Brad Figg ]

  * hyper-v -- add hid and fb drivers to linux-virtual
    - LP: #1444179

  [ Upstream Kernel Changes ]

  * DT doc: net: cpsw mac-address is optional
    - LP: #1452628
  * net: cpsw: Add missing return value
    - LP: #1452628
  * net: cpsw: header, Add missing include
    - LP: #1452628
  * net: cpsw: Add am33xx MACID readout
    - LP: #1452628
  * am33xx: define syscon control module device node
    - LP: #1452628
  * arm: dts: am33xx, Add syscon phandle to cpsw node
    - LP: #1452628
  * net: cpsw: do not register cpts twice
    - LP: #1452620
  * x86: kvm: Revert "remove sched notifier for cross-cpu migrations"
    - LP: #1450584
  * x86: vdso: fix pvclock races with task migration
    - LP: #1450584
  * n_tty: Fix read buffer overwrite when no newline
    - LP: #1381005, #1454746
  * KVM: x86: Fix lost interrupt on irr_pending race
    - LP: #1454746
  * writeback: add missing INITIAL_JIFFIES init in
    global_update_bandwidth()
    - LP: #1454746
  * nbd: fix possible memory leak
    - LP: #1454746
  * mfd: kempld-core: Fix callback return value check
    - LP: #1454746
  * KVM: nVMX: mask unrestricted_guest if disabled on L0
    - LP: #1454746
  * spi: trigger trace event for message-done before mesg->complete
    - LP: #1454746
  * powerpc/pseries: Little endian fixes for post mobility device tree
    update
    - LP: #1454746
  * net: ethernet: pcnet32: Setup the SRAM and NOUFLO on Am79C97{3, 5}
    - LP: #1454746
  * perf: Fix irq_work 'tail' recursion
    - LP: #1454746
  * arm64: Use the reserved TTBR0 if context switching to the init_mm
    - LP: #1454746
  * selinux: fix sel_write_enforce broken return value
    - LP: #1454746
  * mm: fix anon_vma->degree underflow in anon_vma endless growing
    prevention
    - LP: #1454746
  * mm/memory hotplug: postpone the reset of obsolete pgdat
    - LP: #1454746
  * hfsplus: fix B-tree corruption after insertion at position 0
    - LP: #1454746
  * ARC: SA_SIGINFO ucontext regs off-by-one
    - LP: #1454746
  * writeback: fix possible underflow in write bandwidth calculation
    - LP: #1454746
  * iio: fix drivers that check buffer->scan_mask
    - LP: #1454746
  * iio: inv_mpu6050: Clear timestamps fifo while resetting hardware fifo
    - LP: #1454746
  * iio: core: Fix double free.
    - LP: #1454746
  * USB: ftdi_sio: Added custom PID for Synapse Wireless product
    - LP: #1454746
  * iwlwifi: dvm: run INIT firmware again upon .start()
    - LP: #1454746
  * USB: keyspan_pda: add new device id
    - LP: #1454746
  * cifs: smb2_clone_range() - exit on unhandled error
    - LP: #1454746
  * cifs: fix use-after-free bug in find_wri...

[Douglas Roffel (douglas-roffel)]

I believe that this issue has reappeared in 3.13.0-62-generic, i'm getting an extremely similar problem on that kernel version.

[Douglas Roffel (douglas-roffel)]

Specifically, the edit history for https://github.com/torvalds/linux/commits/master/arch/x86/kernel/pvclock.c (one of the files that the parent mentioned needed patching for the fix) shows that the changes added for the fix were removed one month later.

[Christopher M. Penalver (penalvch)]

Douglas Roffel, as this report is closed, if you need a fix please file a new report via a terminal:
ubuntu-bug linux

Please feel free to subscribe me to it.