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[Bug 1481357] Re: [LTCTest][Kernel][OP810]Ubuntu14.04.3: kernel call trace while continuously switching between smt on/off and changing subcores

 

This bug was fixed in the package linux - 3.19.0-51.57

---------------
linux (3.19.0-51.57) vivid; urgency=low

  [ Seth Forshee ]

  * SAUCE: cred: Add clone_cred() interface
    - LP: #1531747, #1534961, #1535150
    - CVE-2016-1575 CVE-2016-1576
  * SAUCE: overlayfs: Use mounter's credentials instead of selectively
    raising caps
    - LP: #1531747, #1534961, #1535150
    - CVE-2016-1575 CVE-2016-1576
  * SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.*
    xattrs
    - LP: #1531747, #1534961, #1535150
    - CVE-2016-1575 CVE-2016-1576
  * SAUCE: overlayfs: Be more careful about copying up sxid files
    - LP: #1534961, #1535150
    - CVE-2016-1575 CVE-2016-1576
  * SAUCE: overlayfs: Propogate nosuid from lower and upper mounts
    - LP: #1534961, #1535150
    - CVE-2016-1575 CVE-2016-1576

linux (3.19.0-50.56) vivid; urgency=low

  [ Brad Figg ]

  * Release Tracking Bug
    - LP: #1540576

  [ J. R. Okajima ]

  * SAUCE: ubuntu: aufs: tiny, extract a new func xino_fwrite_wkq()
    - LP: #1533043
  * SAUCE: ubuntu: aufs: for 4.3, XINO handles EINTR from the dying process
    - LP: #1533043

  [ John Johansen ]

  * SAUCE: (no-up): apparmor: fix for failed mediation of socket that is
    being shutdown
    - LP: #1446906

  [ Upstream Kernel Changes ]

  * drivers/base/memory.c: fix kernel warning during memory hotplug on
    ppc64
    - LP: #1463654
  * sched/wait: Fix signal handling in bit wait helpers
    - LP: #1537859
  * sched/wait: Fix the signal handling fix
    - LP: #1537859
  * ARC: Fix silly typo in MAINTAINERS file
    - LP: #1537859
  * ip6mr: call del_timer_sync() in ip6mr_free_table()
    - LP: #1537859
  * gre6: allow to update all parameters via rtnl
    - LP: #1537859
  * atl1c: Improve driver not to do order 4 GFP_ATOMIC allocation
    - LP: #1537859
  * sctp: use the same clock as if sock source timestamps were on
    - LP: #1537859
  * sctp: update the netstamp_needed counter when copying sockets
    - LP: #1537859
  * sctp: also copy sk_tsflags when copying the socket
    - LP: #1537859
  * net: qca_spi: fix transmit queue timeout handling
    - LP: #1537859
  * ipv6: sctp: clone options to avoid use after free
    - LP: #1537859
  * net: add validation for the socket syscall protocol argument
    - LP: #1537859
  * sh_eth: fix kernel oops in skb_put()
    - LP: #1537859
  * net: fix IP early demux races
    - LP: #1537859
  * vlan: Fix untag operations of stacked vlans with REORDER_HEADER off
    - LP: #1537859
  * skbuff: Fix offset error in skb_reorder_vlan_header
    - LP: #1537859
  * pptp: verify sockaddr_len in pptp_bind() and pptp_connect()
    - LP: #1537859
  * bluetooth: Validate socket address length in sco_sock_bind().
    - LP: #1537859
  * fou: clean up socket with kfree_rcu
    - LP: #1537859
  * af_unix: Revert 'lock_interruptible' in stream receive code
    - LP: #1537859
  * KEYS: Fix race between read and revoke
    - LP: #1537859
  * tools: Add a "make all" rule
    - LP: #1537859
  * efi: Disable interrupts around EFI calls, not in the epilog/prolog
    calls
    - LP: #1537859
  * fuse: break infinite loop in fuse_fill_write_pages()
    - LP: #1537859
  * usb: gadget: pxa27x: fix suspend callback
    - LP: #1537859
  * iio: fix some warning messages
    - LP: #1537859
  * USB: cp210x: Remove CP2110 ID from compatibility list
    - LP: #1537859
  * USB: cdc_acm: Ignore Infineon Flash Loader utility
    - LP: #1537859
  * ext4: Fix handling of extended tv_sec
    - LP: #1537859
  * jbd2: Fix unreclaimed pages after truncate in data=journal mode
    - LP: #1537859
  * drm/ttm: Fixed a read/write lock imbalance
    - LP: #1537859
  * i2c: mv64xxx: The n clockdiv factor is 0 based on sunxi SoCs
    - LP: #1537859
  * AHCI: Fix softreset failed issue of Port Multiplier
    - LP: #1537859
  * sata_sil: disable trim
    - LP: #1537859
  * usb-storage: Fix scsi-sd failure "Invalid field in cdb" for USB adapter
    JMicron
    - LP: #1537859
  * staging: lustre: echo_copy.._lsm() dereferences userland pointers
    directly
    - LP: #1537859
  * irqchip/versatile-fpga: Fix PCI IRQ mapping on Versatile PB
    - LP: #1537859
  * usb: core : hub: Fix BOS 'NULL pointer' kernel panic
    - LP: #1537859
  * USB: whci-hcd: add check for dma mapping error
    - LP: #1537859
  * usb: Use the USB_SS_MULT() macro to decode burst multiplier for log
    message
    - LP: #1537859
  * xen/events/fifo: Consume unprocessed events when a CPU dies
    - LP: #1537859
  * dm btree: fix leak of bufio-backed block in btree_split_sibling error
    path
    - LP: #1537859
  * ARM: 8465/1: mm: keep reserved ASIDs in sync with mm after multiple
    rollovers
    - LP: #1537859
  * perf: Fix PERF_EVENT_IOC_PERIOD deadlock
    - LP: #1537859
  * usb: xhci: fix config fail of FS hub behind a HS hub with MTT
    - LP: #1537859
  * ALSA: rme96: Fix unexpected volume reset after rate changes
    - LP: #1537859
  * net: mvpp2: fix missing DMA region unmap in egress processing
    - LP: #1537859
  * net: mvpp2: fix buffers' DMA handling on RX path
    - LP: #1537859
  * net: mvpp2: fix refilling BM pools in RX path
    - LP: #1537859
  * dmaengine: at_xdmac: fix macro typo
    - LP: #1537859
  * ALSA: hda - Add inverted dmic for Packard Bell DOTS
    - LP: #1523232, #1537859
  * vhost: relax log address alignment
    - LP: #1537859
  * virtio: fix memory leak of virtio ida cache layers
    - LP: #1537859
  * IB/srp: Fix a memory leak
    - LP: #1537859
  * IB/srp: Fix possible send queue overflow
    - LP: #1537859
  * ALSA: hda - Fixing speaker noise on the two latest thinkpad models
    - LP: #1523517, #1537859
  * 9p: ->evict_inode() should kick out ->i_data, not ->i_mapping
    - LP: #1537859
  * radeon/cik: Fix GFX IB test on Big-Endian
    - LP: #1537859
  * radeon: Fix VCE ring test for Big-Endian systems
    - LP: #1537859
  * radeon: Fix VCE IB test on Big-Endian systems
    - LP: #1537859
  * video: fbdev: fsl: Fix kernel crash when diu_ops is not implemented
    - LP: #1537859
  * crypto: skcipher - Copy iv from desc even for 0-len walks
    - LP: #1537859
  * ALSA: hda - Fix noise problems on Thinkpad T440s
    - LP: #1537859
  * dm thin metadata: fix bug when taking a metadata snapshot
    - LP: #1537859
  * dm space map metadata: fix ref counting bug when bootstrapping a new
    space map
    - LP: #1537859
  * ipmi: move timer init to before irq is setup
    - LP: #1537859
  * ASoC: es8328: Fix deemphasis values
    - LP: #1537859
  * KVM: PPC: Book3S HV: Prohibit setting illegal transaction state in MSR
    - LP: #1537859
  * rfkill: copy the name into the rfkill struct
    - LP: #1537859
  * dm btree: fix bufio buffer leaks in dm_btree_del() error path
    - LP: #1537859
  * ses: Fix problems with simple enclosures
    - LP: #1537859
  * vgaarb: fix signal handling in vga_get()
    - LP: #1537859
  * ASoC: davinci-mcasp: Fix XDATA check in mcasp_start_tx
    - LP: #1537859
  * ARM: dts: vf610: use reset values for L2 cache latencies
    - LP: #1537859
  * ses: fix additional element traversal bug
    - LP: #1537859
  * xhci: fix usb2 resume timing and races.
    - LP: #1537859
  * USB: add quirk for devices with broken LPM
    - LP: #1537859
  * powercap / RAPL: fix BIOS lock check
    - LP: #1537859
  * parisc iommu: fix panic due to trying to allocate too large region
    - LP: #1537859
  * mm: hugetlb: fix hugepage memory leak caused by wrong reserve count
    - LP: #1537859
  * vmstat: Reduce time interval to stat update on idle cpu
    - LP: #1537859
  * mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't
    make any progress
    - LP: #1537859
  * mm: hugetlb: call huge_pte_alloc() only if ptep is null
    - LP: #1537859
  * drivers/base/memory.c: prohibit offlining of memory blocks with missing
    sections
    - LP: #1537859
  * ocfs2: fix SGID not inherited issue
    - LP: #1537859
  * sh64: fix __NR_fgetxattr
    - LP: #1537859
  * ASoC: wm8974: set cache type for regmap
    - LP: #1537859
  * n_tty: Fix poll() after buffer-limited eof push read
    - LP: #1537859
  * tty: Fix GPF in flush_to_ldisc()
    - LP: #1537859
  * genirq: Prevent chip buslock deadlock
    - LP: #1537859
  * ALSA: usb-audio: Add a more accurate volume quirk for AudioQuest
    DragonFly
    - LP: #1537859
  * ARM: dts: imx6: Fix Ethernet PHY mode on Ventana boards
    - LP: #1537859
  * ARM: 8471/1: need to save/restore arm register(r11) when it is
    corrupted
    - LP: #1537859
  * ALSA: hda - Add a fixup for Thinkpad X1 Carbon 2nd
    - LP: #1537859
  * spi: fix parent-device reference leak
    - LP: #1537859
  * scripts: recordmcount: break hardlinks
    - LP: #1537859
  * dma-debug: Fix dma_debug_entry offset calculation
    - LP: #1537859
  * ftrace/scripts: Have recordmcount copy the object file
    - LP: #1537859
  * ARC: dw2 unwind: Reinstante unwinding out of modules
    - LP: #1537859
  * ARC: dw2 unwind: Ignore CIE version !=1 gracefully instead of bailing
    - LP: #1537859
  * powerpc/powernv: pr_warn_once on unsupported OPAL_MSG type
    - LP: #1537859
  * ALSA: hda - Set SKL+ hda controller power at freeze() and thaw()
    - LP: #1537859
  * s390/dis: Fix handling of format specifiers
    - LP: #1537859
  * airspy: increase USB control message buffer size
    - LP: #1537859
  * USB: ipaq.c: fix a timeout loop
    - LP: #1537859
  * USB: fix invalid memory access in hub_activate()
    - LP: #1537859
  * x86/mce: Ensure offline CPUs don't participate in rendezvous process
    - LP: #1537859
  * i2c: rcar: disable runtime PM correctly in slave mode
    - LP: #1537859
  * parisc: Fix syscall restarts
    - LP: #1537859
  * ALSA: hda/realtek - Fix silent headphone output on MacPro 4,1 (v2)
    - LP: #1537859
  * MIPS: uaccess: Fix strlen_user with EVA
    - LP: #1537859
  * ASoC: arizona: Fix bclk for sample rates that are multiple of 4kHz
    - LP: #1537859
  * arm: fix handling of F_OFD_... in oabi_fcntl64()
    - LP: #1537859
  * ocfs2: fix BUG when calculate new backup super
    - LP: #1537859
  * mm/memory_hotplug.c: check for missing sections in
    test_pages_in_a_zone()
    - LP: #1537859
  * ftrace/scripts: Fix incorrect use of sprintf in recordmcount
    - LP: #1537859
  * tracing: Fix setting of start_index in find_next()
    - LP: #1537859
  * tile: provide CONFIG_PAGE_SIZE_64KB etc for tilepro
    - LP: #1537859
  * ARM: versatile: fix MMC/SD interrupt assignment
    - LP: #1537859
  * async_tx: use GFP_NOWAIT rather than GFP_IO
    - LP: #1537859
  * dts: vt8500: Add SDHC node to DTS file for WM8650
    - LP: #1537859
  * ftrace/module: Call clean up function when module init fails early
    - LP: #1537859
  * vmstat: allocate vmstat_wq before it is used
    - LP: #1537859
  * usb: musb: USB_TI_CPPI41_DMA requires dmaengine support
    - LP: #1537859
  * sctp: convert sack_needed and sack_generation to bits
    - LP: #1537859
  * sctp: start t5 timer only when peer rwnd is 0 and local state is
    SHUTDOWN_PENDING
    - LP: #1537859
  * pinctrl: bcm2835: Fix initial value for direction_output
    - LP: #1537859
  * net: phy: mdio-mux: Check return value of mdiobus_alloc()
    - LP: #1537859
  * sh_eth: fix TX buffer byte-swapping
    - LP: #1537859
  * mISDN: fix a loop count
    - LP: #1537859
  * amd-xgbe: fix a couple timeout loops
    - LP: #1537859
  * qlcnic: fix a timeout loop
    - LP: #1537859
  * ser_gigaset: fix deallocation of platform device structure
    - LP: #1537859
  * net: fix warnings in 'make htmldocs' by moving macro definition out of
    field declaration
    - LP: #1537859
  * net/mlx4_en: Remove dependency between timestamping capability and
    service_task
    - LP: #1537859
  * net/mlx4_en: Fix HW timestamp init issue upon system startup
    - LP: #1537859
  * include/linux/mmdebug.h: should include linux/bug.h
    - LP: #1537859
  * ipv6/addrlabel: fix ip6addrlbl_get()
    - LP: #1537859
  * ASoC: Use nested lock for snd_soc_dapm_mutex_lock
    - LP: #1537859
  * net: filter: make JITs zero A for SKF_AD_ALU_XOR_X
    - LP: #1537859
  * net: sched: fix missing free per cpu on qstats
    - LP: #1537859
  * net: possible use after free in dst_release
    - LP: #1537859
  * kvm: x86: only channel 0 of the i8254 is linked to the HPET
    - LP: #1537859
  * firmware: dmi_scan: Fix UUID endianness for SMBIOS >= 2.6
    - LP: #1537859
  * Linux 3.19.8-ckt13
    - LP: #1537859
  * hotplugcpu: Avoid deadlocks by waking active_writer
    - LP: #1481357
  * xfrm: dst_entries_init() per-net dst_ops
    - LP: #1486670

 -- Luis Henriques <luis.henriques@xxxxxxxxxxxxx>  Fri, 19 Feb 2016
11:12:52 +0000

** Changed in: linux (Ubuntu Vivid)
       Status: Fix Committed => Fix Released

** CVE added: http://www.cve.mitre.org/cgi-
bin/cvename.cgi?name=2016-1575

** CVE added: http://www.cve.mitre.org/cgi-
bin/cvename.cgi?name=2016-1576

-- 
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https://bugs.launchpad.net/bugs/1481357

Title:
  [LTCTest][Kernel][OP810]Ubuntu14.04.3: kernel call trace while
  continuously switching between smt on/off and changing subcores

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Vivid:
  Fix Released
Status in linux source package in Wily:
  Fix Released
Status in linux source package in Xenial:
  Fix Released

Bug description:
  == Comment: #0 - Satheesh Rajendran <satheera@xxxxxxxxxx> - 2015-07-14 02:32:22 ==
  While running the below script, and nothing else was running in the system, host got the kernel call traces after around 15~20 mins

  #!/bin/bash -x
  while true;
  do for i in 1 2 4;
  do ppc64_cpu  --subcores-per-core=$i;
  ppc64_cpu --info
  ppc64_cpu --smt=off;
  ppc64_cpu --info
  sleep 1;
  lscpu
  ppc64_cpu --smt=on;
  ppc64_cpu --info
  sleep 1;
  lscpu
  done;
  sleep 1;
  done

  
  Environment:
  ------------------
  $ cat /etc/issue
  Ubuntu 14.04.2 LTS \n \l

  $ uname -a
  Linux tul8fp 3.19.0-22-generic #22~14.04.1-Ubuntu SMP Wed Jun 17 10:03:39 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux

  $ lscpu
  Architecture:          ppc64le
  Byte Order:            Little Endian
  CPU(s):                160
  On-line CPU(s) list:   0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,132,136,138-159
  Off-line CPU(s) list:  1-3,5-7,9-11,13-15,17-19,21-23,25-27,29-31,33-35,37-39,41-43,45-47,49-51,53-55,57-59,61-63,65-67,69-71,73-75,77-79,81-83,85-87,89-91,93-95,97-99,101-103,105-107,109-111,113-115,117-119,121-123,125-127,129-131,133-135,137
  Thread(s) per core:    2
  Core(s) per socket:    10
  Socket(s):             2
  NUMA node(s):          2
  Model:                 8335-GTA
  L1d cache:             64K
  L1i cache:             32K
  L2 cache:              512K
  L3 cache:              8192K
  NUMA node0 CPU(s):     0,4,88,92,96,100,104,108,112,116,120,124,128,132,136,138-159
  NUMA node8 CPU(s):     8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84

  $ tail -10 /proc/cpuinfo 
  processor	: 159
  cpu		: POWER8 (raw), altivec supported
  clock		: 2693.000000MHz
  revision	: 2.0 (pvr 004d 0200)

  timebase	: 512000000
  platform	: PowerNV
  model		: 8335-GTA        
  machine		: PowerNV 8335-GTA        
  firmware	: OPAL v3

  Logs:-
  ---------

  
  # dmesg
  [79081.074088] INFO: task irqbalance:1897 blocked for more than 120 seconds.
  [79081.074333]       Not tainted 3.19.0-22-generic #22~14.04.1-Ubuntu
  [79081.074388] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [79081.074449] irqbalance      D 00003fff9ac39d3c     0  1897      1 0x00040000
  [79081.074454] Call Trace:
  [79081.074470] [c0000007e8d035f0] [00003fff9af50000] 0x3fff9af50000 (unreliable)
  [79081.074477] [c0000007e8d037c0] [c000000000015934] __switch_to+0x204/0x350
  [79081.074482] [c0000007e8d03820] [c000000000a11508] __schedule+0x368/0x8d0
  [79081.074486] --- interrupt: 1000ba30 at 0xc0000007e8d039f0
  [79081.074486]     LR = 0x10026a6c1d0
  [79081.074490] [c0000007e8d03a40] [c000000000a120a0] schedule_preempt_disabled+0x20/0x30 (unreliable)
  [79081.074494] [c0000007e8d03a60] [c000000000a1420c] __mutex_lock_slowpath+0xfc/0x1f0
  [79081.074497] [c0000007e8d03ae0] [c000000000a1436c] mutex_lock+0x6c/0x70
  [79081.074501] [c0000007e8d03b10] [c00000000064488c] online_show+0x3c/0x90
  [79081.074503] [c0000007e8d03b90] [c000000000644fec] dev_attr_show+0x5c/0xc0
  [79081.074508] [c0000007e8d03bd0] [c00000000035b7f4] sysfs_kf_seq_show+0x114/0x200
  [79081.074511] [c0000007e8d03c20] [c0000000003591e4] kernfs_seq_show+0x54/0x70
  [79081.074515] [c0000007e8d03c50] [c0000000002e74fc] seq_read+0xec/0x500
  [79081.074519] [c0000007e8d03cf0] [c00000000035a474] kernfs_fop_read+0x184/0x220
  [79081.074523] [c0000007e8d03d50] [c0000000002b520c] __vfs_read+0x6c/0x120
  [79081.074527] [c0000007e8d03d90] [c0000000002b5364] vfs_read+0xa4/0x1c0
  [79081.074530] [c0000007e8d03de0] [c0000000002b54ec] SyS_read+0x6c/0x110
  [79081.074534] [c0000007e8d03e30] [c000000000009258] system_call+0x38/0xd0
  [79081.074546] INFO: task ppc64_cpu:111047 blocked for more than 120 seconds.
  [79081.074597]       Not tainted 3.19.0-22-generic #22~14.04.1-Ubuntu
  [79081.074802] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [79081.074865] ppc64_cpu       D 00003fff82892d08     0 111047 109995 0x00040000
  [79081.074868] Call Trace:
  [79081.074871] [c000000f1c67f680] [c000000f1c67f710] 0xc000000f1c67f710 (unreliable)
  [79081.074875] [c000000f1c67f850] [c000000000015934] __switch_to+0x204/0x350
  [79081.074878] [c000000f1c67f8b0] [c000000000a11508] __schedule+0x368/0x8d0
  [79081.074882] [c000000f1c67fad0] [c0000000000aff10] cpu_hotplug_begin+0xa0/0xb0
  [79081.074887] [c000000f1c67fb10] [c00000000020b0a0] _cpu_down+0xb0/0x3a0
  [79081.074890] [c000000f1c67fbd0] [c00000000020b3e8] cpu_down+0x58/0xa0
  [79081.074894] [c000000f1c67fc00] [c00000000064fa0c] cpu_subsys_offline+0x2c/0x50
  [79081.074897] [c000000f1c67fc30] [c000000000647aa4] device_offline+0x104/0x140
  [79081.074900] [c000000f1c67fc70] [c000000000647c6c] online_store+0x6c/0xc0
  [79081.074904] [c000000f1c67fcc0] [c000000000643ab8] dev_attr_store+0x68/0xa0
  [79081.074907] [c000000f1c67fd00] [c00000000035b350] sysfs_kf_write+0x80/0xb0
  [79081.074910] [c000000f1c67fd40] [c00000000035a28c] kernfs_fop_write+0x18c/0x1f0
  [79081.074914] [c000000f1c67fd90] [c0000000002b474c] vfs_write+0xdc/0x260
  [79081.074917] [c000000f1c67fde0] [c0000000002b55fc] SyS_write+0x6c/0x110
  [79081.074921] [c000000f1c67fe30] [c000000000009258] system_call+0x38/0xd0
  [79201.074065] INFO: task irqbalance:1897 blocked for more than 120 seconds.
  [79201.074312]       Not tainted 3.19.0-22-generic #22~14.04.1-Ubuntu
  [79201.074361] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [79201.074421] irqbalance      D 00003fff9ac39d3c     0  1897      1 0x00040000
  [79201.074424] Call Trace:
  [79201.074428] [c0000007e8d035f0] [00003fff9af50000] 0x3fff9af50000 (unreliable)
  [79201.074432] [c0000007e8d037c0] [c000000000015934] __switch_to+0x204/0x350
  [79201.074436] [c0000007e8d03820] [c000000000a11508] __schedule+0x368/0x8d0
  [79201.074439] --- interrupt: 1000ba30 at 0xc0000007e8d039f0
  [79201.074439]     LR = 0x10026a6c1d0
  [79201.074443] [c0000007e8d03a40] [c000000000a120a0] schedule_preempt_disabled+0x20/0x30 (unreliable)
  [79201.074447] [c0000007e8d03a60] [c000000000a1420c] __mutex_lock_slowpath+0xfc/0x1f0
  [79201.074450] [c0000007e8d03ae0] [c000000000a1436c] mutex_lock+0x6c/0x70
  [79201.074453] [c0000007e8d03b10] [c00000000064488c] online_show+0x3c/0x90
  [79201.074456] [c0000007e8d03b90] [c000000000644fec] dev_attr_show+0x5c/0xc0
  [79201.074459] [c0000007e8d03bd0] [c00000000035b7f4] sysfs_kf_seq_show+0x114/0x200
  [79201.074462] [c0000007e8d03c20] [c0000000003591e4] kernfs_seq_show+0x54/0x70
  [79201.074465] [c0000007e8d03c50] [c0000000002e74fc] seq_read+0xec/0x500
  [79201.074468] [c0000007e8d03cf0] [c00000000035a474] kernfs_fop_read+0x184/0x220
  [79201.074472] [c0000007e8d03d50] [c0000000002b520c] __vfs_read+0x6c/0x120
  [79201.074475] [c0000007e8d03d90] [c0000000002b5364] vfs_read+0xa4/0x1c0
  [79201.074479] [c0000007e8d03de0] [c0000000002b54ec] SyS_read+0x6c/0x110
  [79201.074482] [c0000007e8d03e30] [c000000000009258] system_call+0x38/0xd0
  [79201.074499] INFO: task ppc64_cpu:111047 blocked for more than 120 seconds.
  [79201.074638]       Not tainted 3.19.0-22-generic #22~14.04.1-Ubuntu
  [79201.074726] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [79201.074786] ppc64_cpu       D 00003fff82892d08     0 111047 109995 0x00040000
  [79201.074789] Call Trace:
  [79201.074792] [c000000f1c67f680] [c000000f1c67f710] 0xc000000f1c67f710 (unreliable)
  [79201.074795] [c000000f1c67f850] [c000000000015934] __switch_to+0x204/0x350
  [79201.074798] [c000000f1c67f8b0] [c000000000a11508] __schedule+0x368/0x8d0
  [79201.074802] [c000000f1c67fad0] [c0000000000aff10] cpu_hotplug_begin+0xa0/0xb0
  [79201.074805] [c000000f1c67fb10] [c00000000020b0a0] _cpu_down+0xb0/0x3a0
  [79201.074808] [c000000f1c67fbd0] [c00000000020b3e8] cpu_down+0x58/0xa0
  [79201.074811] [c000000f1c67fc00] [c00000000064fa0c] cpu_subsys_offline+0x2c/0x50
  [79201.074814] [c000000f1c67fc30] [c000000000647aa4] device_offline+0x104/0x140
  [79201.074817] [c000000f1c67fc70] [c000000000647c6c] online_store+0x6c/0xc0
  [79201.074821] [c000000f1c67fcc0] [c000000000643ab8] dev_attr_store+0x68/0xa0
  [79201.074824] [c000000f1c67fd00] [c00000000035b350] sysfs_kf_write+0x80/0xb0
  [79201.074827] [c000000f1c67fd40] [c00000000035a28c] kernfs_fop_write+0x18c/0x1f0
  [79201.074831] [c000000f1c67fd90] [c0000000002b474c] vfs_write+0xdc/0x260
  [79201.074834] [c000000f1c67fde0] [c0000000002b55fc] SyS_write+0x6c/0x110
  [79201.074837] [c000000f1c67fe30] [c000000000009258] system_call+0x38/0xd0
  [79321.074029] INFO: task irqbalance:1897 blocked for more than 120 seconds.
  [79321.074269]       Not tainted 3.19.0-22-generic #22~14.04.1-Ubuntu
  [79321.074319] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [79321.074378] irqbalance      D 00003fff9ac39d3c     0  1897      1 0x00040000
  [79321.074382] Call Trace:
  [79321.074386] [c0000007e8d035f0] [00003fff9af50000] 0x3fff9af50000 (unreliable)
  [79321.074390] [c0000007e8d037c0] [c000000000015934] __switch_to+0x204/0x350
  [79321.074393] [c0000007e8d03820] [c000000000a11508] __schedule+0x368/0x8d0
  [79321.074396] --- interrupt: 1000ba30 at 0xc0000007e8d039f0
  [79321.074396]     LR = 0x10026a6c1d0
  [79321.074400] [c0000007e8d03a40] [c000000000a120a0] schedule_preempt_disabled+0x20/0x30 (unreliable)
  [79321.074404] [c0000007e8d03a60] [c000000000a1420c] __mutex_lock_slowpath+0xfc/0x1f0
  [79321.074407] [c0000007e8d03ae0] [c000000000a1436c] mutex_lock+0x6c/0x70
  [79321.074410] [c0000007e8d03b10] [c00000000064488c] online_show+0x3c/0x90
  [79321.074412] [c0000007e8d03b90] [c000000000644fec] dev_attr_show+0x5c/0xc0
  [79321.074416] [c0000007e8d03bd0] [c00000000035b7f4] sysfs_kf_seq_show+0x114/0x200
  [79321.074419] [c0000007e8d03c20] [c0000000003591e4] kernfs_seq_show+0x54/0x70
  [79321.074422] [c0000007e8d03c50] [c0000000002e74fc] seq_read+0xec/0x500
  [79321.074425] [c0000007e8d03cf0] [c00000000035a474] kernfs_fop_read+0x184/0x220
  [79321.074429] [c0000007e8d03d50] [c0000000002b520c] __vfs_read+0x6c/0x120
  [79321.074432] [c0000007e8d03d90] [c0000000002b5364] vfs_read+0xa4/0x1c0
  [79321.074436] [c0000007e8d03de0] [c0000000002b54ec] SyS_read+0x6c/0x110
  [79321.074439] [c0000007e8d03e30] [c000000000009258] system_call+0x38/0xd0
  [79321.074453] INFO: task ppc64_cpu:111047 blocked for more than 120 seconds.

  == Comment: #1 - Satheesh Rajendran <satheera@xxxxxxxxxx> - 2015-07-14 02:34:55 ==
  Tried to get sosreport but the same got stuck during info gathering at processor.

  # sosreport 
  ...
  Please enter your first initial and last name [tul8fp]: satheesh
  Please enter the case number that you are generating this report for: trace

   Running plugins. Please wait ...

    Running 51/64: processor...

  == Comment: #3 - Ranjal G. Shenoy <ranjshen@xxxxxxxxxx> - 2015-07-14 05:18:17 ==
  Hi Sandhya,

  From the call trace it looks like ppc64_task which is trying to
  offline a cpu is blocked inside cpu_hotplug_begin(). This happens when
  someone else is trying to prevent a cpu-hotplug using the
  get_online_cpus()/put_online_cpus() call. It is not clear from the
  logs what is that entity that's preventing this.

  That said,  I don't think the patch that you are referring to has
  anything to do with it. The problem lies elsewhere. If you see that
  the ppc64_cpu task is not making any progress at all, then it might be
  prudent to enable lockdep which will at least list out all the locks
  that are held at any point.

  == Comment: #4 - Ranjal G. Shenoy <ranjshen@xxxxxxxxxx> - 2015-07-14 05:48:39 ==
  (In reply to comment #3)
  > Hi Sandhya,
  > 
  > From the call trace it looks like ppc64_task which is trying to offline a
  > cpu is blocked inside cpu_hotplug_begin(). This happens when someone else is
  > trying to prevent a cpu-hotplug using the
  > get_online_cpus()/put_online_cpus() call. It is not clear from the logs what
  > is that entity that's preventing this. 
  > 
  > That said,  I don't think the patch that you are referring to has anything
  > to do with it. The problem lies elsewhere. If you see that the ppc64_cpu
  > task is not making any progress at all, then it might be prudent to enable
  > lockdep which will at least list out all the locks that are held at any
  > point.

  To add to that, I recall seeing a similar issue where cpu-offline
  operation was blocking inside cpu_hotplug_begin. The fix for that is
  present in the mainline with commit id : 87af9e7ff9. You can try
  backporting that one.

  == Comment: #13 - Satheesh Rajendran <satheera@xxxxxxxxxx> - 2015-07-27 12:06:19 ==
  Ran script mentioned in bug description continuously for 6 hours and not have seen the mentioned call traces.

  Once this fix is available as part of ubuntu14.04.3 released kernel,
  this bug can be closed.

  Thanks in advance.

  Regards,
  -Satheesh.

  == Comment: #14 - Brahadambal Srinivasan <brsriniv@xxxxxxxxxx> - 2015-08-04 09:31:21 ==
  Cherry picked bug backported to the trusty kernel to resolve the issue reported in this bug

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