[Openstack] BUG: soft lockup messages

Matej Mailing mailing at tam.si
Sun Jan 4 12:36:17 UTC 2015


2015-01-03 17:56 GMT+01:00 John Griffith <john.griffith at solidfire.com>:
> On Sat, Jan 3, 2015 at 5:05 AM, Matej Mailing <mailing at tam.si> wrote:
>> Hi,
>>
>> we are experiencing randomly-timed soft lockup messages in different
>> instances (running CentOS, Ubuntu, etc.) with different processes and
>> on different compute nodes. I suspect that access to the cinder
>> storage via NFS could be the cause of issue, but then perhaps all the
>> instances would trigger the error message on the same time? Currently
>> they don't and no higher access loads are repoted on the NFS server
>> itself, neither the load is higher at those times ...
>> What are the best methods to debug this error? Any suggestions and
>> expeiences on fixing it will be very welcome :-)
>>
>> Thanks,
>> Matej
>>
>> _______________________________________________
>> Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
>> Post to     : openstack at lists.openstack.org
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>
> Hi Matej,
>
> I'm assuming the kernel logs indicate NFS as the culprit here? What
> sort of IO load are you seeing on the system when these are
> encountered?
>
> A quick search on "soft lockup nfs" has a pretty lengthy list of
> results including some setting recommendations etc.  Maybe start
> there?
>
> Thanks,
> John

Hello John,

thank you very much for your answer. I can't find anything at all in
the compute node's logs and my NFS-idea is just a guess
actually.Example entry from Ubuntu instances is like:

Jan  3 10:41:44 postar kernel: [303154.352793] NMI watchdog: BUG: soft
lockup - CPU#3 stuck for 45s! [mysqld:4601]
Jan  3 10:41:44 postar kernel: [303154.352890] Modules linked in:
xt_hl ip6t_rt nf_conntrack_ipv6 nf_defrag_ipv6 ipt_REJECT
nf_reject_ipv4 xt_limit xt_tcpudp xt_addrtype nf_conntrack_ipv4
nf_defrag_ipv4 xt_state ip6table_filter ip6_tables nfsd nfs_acl
auth_rpcgss nf_conntrack_netbios_ns
nf_conntrack_broadcast nfs nf_nat_ftp nf_nat ppdev nf_conntrack_ftp
nf_conntrack fscache parport_pc parport lockd joydev pvpanic
iptable_filter cirrus ip_tables 8250_fintek ttm psmouse drm_kms_helper
sunrpc x_tables serio_raw hid_generic drm grace mac_hid sysimgblt
sysfillrect syscopyarea
i2c_piix4 usbhid hid floppy
Jan  3 10:41:44 postar kernel: [303154.352958] CPU: 3 PID: 4601 Comm:
mysqld Not tainted 3.18.1-031801-generic #201412170637
Jan  3 10:41:44 postar kernel: [303154.352961] Hardware name:
OpenStack Foundation OpenStack Nova, BIOS Bochs 01/01/2011
Jan  3 10:41:44 postar kernel: [303154.352964] task: ffff880231b63c00
ti: ffff8801e6014000 task.ti: ffff8801e6014000
Jan  3 10:41:44 postar kernel: [303154.352966] RIP:
0010:[<ffffffff813a97dc>]  [<ffffffff813a97dc>]
copy_user_generic_string+0x2c/0x40
Jan  3 10:41:44 postar kernel: [303154.352979] RSP:
0018:ffff8801e6017c90  EFLAGS: 00010246
Jan  3 10:41:44 postar kernel: [303154.352981] RAX: 00000000a2418000
RBX: ffff8801e6017ea0 RCX: 0000000000000200
Jan  3 10:41:44 postar kernel: [303154.352983] RDX: 0000000000000000
RSI: ffff8800a2418000 RDI: 00007fd365b90000
Jan  3 10:41:44 postar kernel: [303154.352985] RBP: ffff8801e6017d08
R08: ffffea000289061c R09: ffff8801e6017ca0
Jan  3 10:41:44 postar kernel: [303154.352987] R10: ffff8800a5c1b258
R11: 0000000000000293 R12: 0000000000000000
Jan  3 10:41:44 postar kernel: [303154.352989] R13: ffff8801e6017ec8
R14: 0000000000001000 R15: 00007fd365b90000
Jan  3 10:41:44 postar kernel: [303154.352995] FS:
00007fd36c28e700(0000) GS:ffff88023fd80000(0000)
knlGS:0000000000000000
Jan  3 10:41:44 postar kernel: [303154.352998] CS:  0010 DS: 0000 ES:
0000 CR0: 0000000080050033
Jan  3 10:41:44 postar kernel: [303154.353000] CR2: 0000000002b9e003
CR3: 00000002317ee000 CR4: 00000000000006e0
Jan  3 10:41:44 postar kernel: [303154.353014] Stack:
Jan  3 10:41:44 postar kernel: [303154.353016]  ffffffff811a0f75
ffff8801e6017d88 ffff8800a5c1b258 ffff8801e6017cc8
Jan  3 10:41:44 postar kernel: [303154.353019]  ffffffff8117864e
ffff8800a2418000 ffffea0002890600 0000000000001000
Jan  3 10:41:44 postar kernel: [303154.353023]  ffff8800a2418000
0000000000000000 ffffea0002890600 ffff880231e4b930
Jan  3 10:41:44 postar kernel: [303154.353026] Call Trace:
Jan  3 10:41:44 postar kernel: [303154.353034]  [<ffffffff811a0f75>] ?
copy_page_to_iter_iovec+0xe5/0x300
Jan  3 10:41:44 postar kernel: [303154.353040]  [<ffffffff8117864e>] ?
find_get_entry+0x1e/0x90
Jan  3 10:41:44 postar kernel: [303154.353044]  [<ffffffff811a14a6>]
copy_page_to_iter+0x16/0x70
Jan  3 10:41:44 postar kernel: [303154.353047]  [<ffffffff81179428>]
do_generic_file_read+0x1f8/0x490
Jan  3 10:41:44 postar kernel: [303154.353051]  [<ffffffff8117a234>]
generic_file_read_iter+0xf4/0x150
Jan  3 10:41:44 postar kernel: [303154.353056]  [<ffffffff810aade1>] ?
update_curr+0x141/0x1f0
Jan  3 10:41:44 postar kernel: [303154.353060]  [<ffffffff810efcd8>] ?
get_futex_key+0x1f8/0x2e0
Jan  3 10:41:44 postar kernel: [303154.353065]  [<ffffffff811eef28>]
new_sync_read+0x78/0xb0
Jan  3 10:41:44 postar kernel: [303154.353068]  [<ffffffff811f013b>]
vfs_read+0xab/0x180
Jan  3 10:41:44 postar kernel: [303154.353071]  [<ffffffff811f0402>]
SyS_pread64+0x92/0xa0
Jan  3 10:41:44 postar kernel: [303154.353077]  [<ffffffff817b376d>]
system_call_fastpath+0x16/0x1b
Jan  3 10:41:44 postar kernel: [303154.353079] Code: 66 90 83 fa 08 72
27 89 f9 83 e1 07 74 15 83 e9 08 f7 d9 29 ca 8a 06 88 07 48 ff c6 48
ff c7 ff c9 75 f2 89 d1 c1 e9 03 83 e2 07 <f3> 48 a5 89 d1 f3 a4 31 c0
66 66 90 c3 0f 1f 80 00 00 00 00 66


and:

Jan  3 10:44:00 postar kernel: [303164.436029] INFO: rcu_sched
detected stalls on CPUs/tasks: { 3} (detected by 0, t=33923 jiffies,
g=1793081, c=1793080, q=0)
Jan  3 10:44:00 postar kernel: [303164.436029] Task dump for CPU 3:
Jan  3 10:44:00 postar kernel: [303164.436029] mysqld          R
running task        0  4601      1 0x00000008
Jan  3 10:44:00 postar kernel: [303164.436029]  0000000000000001
00007fd36286c000 0000000000004000 0000000000004000
Jan  3 10:44:00 postar kernel: [303164.436029]  00007fd36286c000
ffff8801e6017f28 ffffffff811f013b 00007fd36c28ba80
Jan  3 10:44:00 postar kernel: [303164.436029]  ffff8802316eaf01
ffff8802316eaf00 00007fd36286c000 0000000000004000
Jan  3 10:44:00 postar kernel: [303164.436029] Call Trace:
Jan  3 10:44:00 postar kernel: [303164.436029]  [<ffffffff811f013b>] ?
vfs_read+0xab/0x180
Jan  3 10:44:00 postar kernel: [303164.436029]  [<ffffffff811f0402>] ?
SyS_pread64+0x92/0xa0
Jan  3 10:44:00 postar kernel: [303164.436029]  [<ffffffff817b376d>] ?
system_call_fastpath+0x16/0x1b
Jan  3 10:44:00 postar kernel: [303290.052393] INFO: task
jbd2/vda1-8:256 blocked for more than 120 seconds.
Jan  3 10:44:00 postar kernel: [303290.052395]       Tainted: G
     L 3.18.1-031801-generic #201412170637
Jan  3 10:44:00 postar kernel: [303290.052396] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jan  3 10:44:00 postar kernel: [303290.052399] jbd2/vda1-8     D
0000000000000002     0   256      2 0x00000000
Jan  3 10:44:00 postar kernel: [303290.052402]  ffff88023170b6a8
0000000000000046 ffff88023170b648 0000000000f2f754
Jan  3 10:44:00 postar kernel: [303290.052404]  ffff88023170bfd8
0000000000013640 ffff8800baef5f80 0000000000013640
Jan  3 10:44:00 postar kernel: [303290.052406]  ffff8802342ab200
ffff880231b64600 ffff88023170b678 ffff88023fd13f40
Jan  3 10:44:00 postar kernel: [303290.052407] Call Trace:
Jan  3 10:44:00 postar kernel: [303290.052413]  [<ffffffff817af549>]
schedule+0x29/0x70
Jan  3 10:44:00 postar kernel: [303290.052415]  [<ffffffff817af61f>]
io_schedule+0x8f/0xd0
Jan  3 10:44:00 postar kernel: [303290.052419]  [<ffffffff81379f30>]
bt_get+0xf0/0x180
Jan  3 10:44:00 postar kernel: [303290.052423]  [<ffffffff810b4bd0>] ?
prepare_to_wait_event+0x100/0x100
Jan  3 10:44:00 postar kernel: [303290.052425]  [<ffffffff8137a2f2>]
blk_mq_get_tag+0x82/0xd0
Jan  3 10:44:00 postar kernel: [303290.052428]  [<ffffffff813762da>]
__blk_mq_alloc_request+0x2a/0xb0
Jan  3 10:44:00 postar kernel: [303290.052430]  [<ffffffff81377d72>]
blk_mq_map_request+0x182/0x1f0
Jan  3 10:44:00 postar kernel: [303290.052432]  [<ffffffff81377a36>] ?
__blk_mq_run_hw_queue+0xf6/0x260
Jan  3 10:44:00 postar kernel: [303290.052434]  [<ffffffff81378446>]
blk_sq_make_request+0x96/0x310
Jan  3 10:44:00 postar kernel: [303290.052438]  [<ffffffff81369c65>]
generic_make_request.part.75+0x75/0xb0
Jan  3 10:44:00 postar kernel: [303290.052440]  [<ffffffff8136a288>]
generic_make_request+0x68/0x70
Jan  3 10:44:00 postar kernel: [303290.052442]  [<ffffffff8136a316>]
submit_bio+0x86/0x160
Jan  3 10:44:00 postar kernel: [303290.052446]  [<ffffffff81177789>] ?
unlock_page+0x69/0x70
Jan  3 10:44:00 postar kernel: [303290.052449]  [<ffffffff81278b39>]
ext4_io_submit+0x29/0x50
Jan  3 10:44:00 postar kernel: [303290.052451]  [<ffffffff8127427b>]
ext4_writepage+0xcb/0x240
Jan  3 10:44:00 postar kernel: [303290.052454]  [<ffffffff811b16c0>] ?
SyS_msync+0x230/0x230
Jan  3 10:44:00 postar kernel: [303290.052457]  [<ffffffff81182b87>]
__writepage+0x17/0x50
Jan  3 10:44:00 postar kernel: [303290.052460]  [<ffffffff8118323a>]
write_cache_pages+0x20a/0x470
Jan  3 10:44:00 postar kernel: [303290.052462]  [<ffffffff81182b70>] ?
set_page_dirty_lock+0x60/0x60
Jan  3 10:44:00 postar kernel: [303290.052464]  [<ffffffff811834ea>]
generic_writepages+0x4a/0x70
Jan  3 10:44:00 postar kernel: [303290.052468]  [<ffffffff812bb73f>]
journal_submit_data_buffers+0xcf/0x180
Jan  3 10:44:00 postar kernel: [303290.052470]  [<ffffffff812bc1c4>]
jbd2_journal_commit_transaction+0x394/0x1440
Jan  3 10:44:00 postar kernel: [303290.052474]  [<ffffffff812c09b3>]
kjournald2+0xb3/0x230
Jan  3 10:44:00 postar kernel: [303290.052476]  [<ffffffff810b4bd0>] ?
prepare_to_wait_event+0x100/0x100
Jan  3 10:44:00 postar kernel: [303290.052478]  [<ffffffff812c0900>] ?
commit_timeout+0x10/0x10
Jan  3 10:44:00 postar kernel: [303290.052481]  [<ffffffff81093a09>]
kthread+0xc9/0xe0
Jan  3 10:44:00 postar kernel: [303290.052483]  [<ffffffff81093940>] ?
flush_kthread_worker+0x90/0x90
Jan  3 10:44:00 postar kernel: [303290.052485]  [<ffffffff817b36bc>]
ret_from_fork+0x7c/0xb0
Jan  3 10:44:00 postar kernel: [303290.052487]  [<ffffffff81093940>] ?
flush_kthread_worker+0x90/0x90
Jan  3 10:44:00 postar kernel: [303290.052498] INFO: task mysqld:2290
blocked for more than 120 seconds.
Jan  3 10:44:00 postar kernel: [303290.052499]       Tainted: G
     L 3.18.1-031801-generic #201412170637
Jan  3 10:44:00 postar kernel: [303290.052499] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jan  3 10:44:00 postar kernel: [303290.052502] mysqld          D
0000000000000002     0  2290      1 0x00000000
Jan  3 10:44:00 postar kernel: [303290.052504]  ffff88023122b9c8
0000000000000082 ffff880200000002 0000000000f2f748
Jan  3 10:44:00 postar kernel: [303290.052506]  ffff88023122bfd8
0000000000013640 ffff880231b98380 0000000000013640
Jan  3 10:44:00 postar kernel: [303290.052508]  ffff880037ab3200
ffff880233142800 ffff88023122b998 ffff88023fd13f40
Jan  3 10:44:00 postar kernel: [303290.052509] Call Trace:
Jan  3 10:44:00 postar kernel: [303290.052511]  [<ffffffff817af549>]
schedule+0x29/0x70
Jan  3 10:44:00 postar kernel: [303290.052531]  [<ffffffff817af61f>]
io_schedule+0x8f/0xd0
Jan  3 10:44:00 postar kernel: [303290.052534]  [<ffffffff81379f30>]
bt_get+0xf0/0x180
Jan  3 10:44:00 postar kernel: [303290.052536]  [<ffffffff810b4bd0>] ?
prepare_to_wait_event+0x100/0x100
Jan  3 10:44:00 postar kernel: [303290.052538]  [<ffffffff8137a2f2>]
blk_mq_get_tag+0x82/0xd0
Jan  3 10:44:00 postar kernel: [303290.052540]  [<ffffffff813762da>]
__blk_mq_alloc_request+0x2a/0xb0
Jan  3 10:44:00 postar kernel: [303290.052542]  [<ffffffff81377d72>]
blk_mq_map_request+0x182/0x1f0
Jan  3 10:44:00 postar kernel: [303290.052545]  [<ffffffff81378446>]
blk_sq_make_request+0x96/0x310
Jan  3 10:44:00 postar kernel: [303290.052547]  [<ffffffff81369c65>]
generic_make_request.part.75+0x75/0xb0
Jan  3 10:44:00 postar kernel: [303290.052549]  [<ffffffff8136a288>]
generic_make_request+0x68/0x70
Jan  3 10:44:00 postar kernel: [303290.052551]  [<ffffffff8136a316>]
submit_bio+0x86/0x160
Jan  3 10:44:00 postar kernel: [303290.052553]  [<ffffffff812b940d>] ?
jbd2__journal_start+0x4d/0x60
Jan  3 10:44:00 postar kernel: [303290.052555]  [<ffffffff81278b39>]
ext4_io_submit+0x29/0x50
Jan  3 10:44:00 postar kernel: [303290.052557]  [<ffffffff81277446>]
ext4_writepages+0x4f6/0x7b0
Jan  3 10:44:00 postar kernel: [303290.052560]  [<ffffffff810efcd8>] ?
get_futex_key+0x1f8/0x2e0
Jan  3 10:44:00 postar kernel: [303290.052563]  [<ffffffff81184730>]
do_writepages+0x20/0x40
Jan  3 10:44:00 postar kernel: [303290.052565]  [<ffffffff81179b29>]
__filemap_fdatawrite_range+0x59/0x60
Jan  3 10:44:00 postar kernel: [303290.052567]  [<ffffffff81179b67>]
filemap_write_and_wait_range+0x37/0x80
Jan  3 10:44:00 postar kernel: [303290.052571]  [<ffffffff8126c3a5>]
ext4_sync_file+0x105/0x290
Jan  3 10:44:00 postar kernel: [303290.052573]  [<ffffffff811f0036>] ?
vfs_write+0x196/0x1f0
Jan  3 10:44:00 postar kernel: [303290.052576]  [<ffffffff8121faa8>]
do_fsync+0x58/0x80
Jan  3 10:44:00 postar kernel: [303290.052578]  [<ffffffff8121fe70>]
SyS_fsync+0x10/0x20
Jan  3 10:44:00 postar kernel: [303290.052580]  [<ffffffff817b376d>]
system_call_fastpath+0x16/0x1b
Jan  3 10:44:00 postar kernel: [303290.052590] INFO: task
kworker/u8:1:22405 blocked for more than 120 seconds.
Jan  3 10:44:00 postar kernel: [303290.052592]       Tainted: G
     L 3.18.1-031801-generic #201412170637
Jan  3 10:44:00 postar kernel: [303290.052592] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jan  3 10:44:00 postar kernel: [303290.052595] kworker/u8:1    D
0000000000000002     0 22405      2 0x00000000
Jan  3 10:44:00 postar kernel: [303290.052600] Workqueue: writeback
bdi_writeback_workfn (flush-253:0)
Jan  3 10:44:00 postar kernel: [303290.052602]  ffff8801f38374c8
0000000000000046 ffff8801f38374b8 0000000000f2f754
Jan  3 10:44:00 postar kernel: [303290.052604]  ffff8801f3837fd8
0000000000013640 ffff8800baef5f80 0000000000013640
Jan  3 10:44:00 postar kernel: [303290.052606]  ffff880231b64600
ffff8801f397d000 ffff8801f3837498 ffff88023fd13f40
Jan  3 10:44:00 postar kernel: [303290.052607] Call Trace:
Jan  3 10:44:00 postar kernel: [303290.052609]  [<ffffffff817af549>]
schedule+0x29/0x70
Jan  3 10:44:00 postar kernel: [303290.052611]  [<ffffffff817af61f>]
io_schedule+0x8f/0xd0
Jan  3 10:44:00 postar kernel: [303290.052614]  [<ffffffff81379f30>]
bt_get+0xf0/0x180
Jan  3 10:44:00 postar kernel: [303290.052616]  [<ffffffff810b4bd0>] ?
prepare_to_wait_event+0x100/0x100
Jan  3 10:44:00 postar kernel: [303290.052618]  [<ffffffff8137a2f2>]
blk_mq_get_tag+0x82/0xd0
Jan  3 10:44:00 postar kernel: [303290.052620]  [<ffffffff813762da>]
__blk_mq_alloc_request+0x2a/0xb0
Jan  3 10:44:00 postar kernel: [303290.052622]  [<ffffffff81377d72>]
blk_mq_map_request+0x182/0x1f0
Jan  3 10:44:00 postar kernel: [303290.052626]  [<ffffffff814692de>] ?
alloc_indirect+0x1e/0x50
Jan  3 10:44:00 postar kernel: [303290.052628]  [<ffffffff81378446>]
blk_sq_make_request+0x96/0x310
Jan  3 10:44:00 postar kernel: [303290.052630]  [<ffffffff81369c65>]
generic_make_request.part.75+0x75/0xb0
Jan  3 10:44:00 postar kernel: [303290.052633]  [<ffffffff8136a288>]
generic_make_request+0x68/0x70
Jan  3 10:44:00 postar kernel: [303290.052634]  [<ffffffff8136a316>]
submit_bio+0x86/0x160
Jan  3 10:44:00 postar kernel: [303290.052638]  [<ffffffff81364e5b>] ?
bio_alloc_bioset+0xbb/0x220
Jan  3 10:44:00 postar kernel: [303290.052641]  [<ffffffff81223ff0>]
_submit_bh+0x110/0x150
Jan  3 10:44:00 postar kernel: [303290.052643]  [<ffffffff81224040>]
submit_bh+0x10/0x20
Jan  3 10:44:00 postar kernel: [303290.052646]  [<ffffffff81225cc0>]
__block_write_full_page.constprop.35+0x1a0/0x380
Jan  3 10:44:00 postar kernel: [303290.052648]  [<ffffffff81226110>] ?
I_BDEV+0x10/0x10
Jan  3 10:44:00 postar kernel: [303290.052650]  [<ffffffff81226110>] ?
I_BDEV+0x10/0x10
Jan  3 10:44:00 postar kernel: [303290.052652]  [<ffffffff81226039>]
block_write_full_page+0xa9/0xe0
Jan  3 10:44:00 postar kernel: [303290.052654]  [<ffffffff81226b38>]
blkdev_writepage+0x18/0x20
Jan  3 10:44:00 postar kernel: [303290.052656]  [<ffffffff81182b87>]
__writepage+0x17/0x50
Jan  3 10:44:00 postar kernel: [303290.052658]  [<ffffffff8118323a>]
write_cache_pages+0x20a/0x470
Jan  3 10:44:00 postar kernel: [303290.052660]  [<ffffffff81182b70>] ?
set_page_dirty_lock+0x60/0x60
Jan  3 10:44:00 postar kernel: [303290.052663]  [<ffffffff811834ea>]
generic_writepages+0x4a/0x70
Jan  3 10:44:00 postar kernel: [303290.052665]  [<ffffffff81184730>]
do_writepages+0x20/0x40
Jan  3 10:44:00 postar kernel: [303290.052668]  [<ffffffff81217fe5>]
__writeback_single_inode+0x45/0x1c0
Jan  3 10:44:00 postar kernel: [303290.052670]  [<ffffffff812199be>]
writeback_sb_inodes+0x22e/0x340
Jan  3 10:44:00 postar kernel: [303290.052673]  [<ffffffff81219b6e>]
__writeback_inodes_wb+0x9e/0xd0
Jan  3 10:44:00 postar kernel: [303290.052675]  [<ffffffff81219e2b>]
wb_writeback+0x28b/0x330
Jan  3 10:44:00 postar kernel: [303290.052678]  [<ffffffff8120ac32>] ?
get_nr_dirty_inodes+0x52/0x80
Jan  3 10:44:00 postar kernel: [303290.052681]  [<ffffffff81219f6f>]
wb_check_old_data_flush+0x9f/0xb0
Jan  3 10:44:00 postar kernel: [303290.052683]  [<ffffffff8121a0b4>]
wb_do_writeback+0x134/0x1c0
Jan  3 10:44:00 postar kernel: [303290.052685]  [<ffffffff810908bf>] ?
set_worker_desc+0x6f/0x80
Jan  3 10:44:00 postar kernel: [303290.052688]  [<ffffffff8121c048>]
bdi_writeback_workfn+0x78/0x1f0
Jan  3 10:44:00 postar kernel: [303290.052729]  [<ffffffff8108d50e>]
process_one_work+0x14e/0x460
Jan  3 10:44:00 postar kernel: [303290.052732]  [<ffffffff8108de8b>]
worker_thread+0x11b/0x3f0
Jan  3 10:44:00 postar kernel: [303290.052735]  [<ffffffff8108dd70>] ?
create_worker+0x1e0/0x1e0
Jan  3 10:44:00 postar kernel: [303290.052737]  [<ffffffff81093a09>]
kthread+0xc9/0xe0
Jan  3 10:44:00 postar kernel: [303290.052739]  [<ffffffff81093940>] ?
flush_kthread_worker+0x90/0x90
Jan  3 10:44:00 postar kernel: [303290.052741]  [<ffffffff817b36bc>]
ret_from_fork+0x7c/0xb0
Jan  3 10:44:00 postar kernel: [303290.052743]  [<ffffffff81093940>] ?
flush_kthread_worker+0x90/0x90

The instance's qcow2 file is on a NFS share, mounted on a compute node.

Different processes are triggering the soft lock-up, what is
interesting is that we see soft lock-ups showing up on the same time
on all the instances running on the same compute node. I will examine
iostat and top outputs closely when it happens, it's relatively hard
to catch that moment since it happens for a relatively short period of
time.

Thank you for any ideas in advance.
Matej




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