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I have server which hung every 2-5 days. dmesg show following situation:

kernel: [490894.231753] INFO: task munin-html:10187 blocked for more than 120 seconds.
kernel: [490894.231799] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: [490894.231843] munin-html    D 0000000000000000     0 10187   9796 0x00000000
kernel: [490894.231878]  ffff88063174b968 0000000000000082 ffff88063174b8d8 0000000000015b80
kernel: [490894.231930]  ffff88063174bfd8 0000000000015b80 ffff88063174bfd8 ffff88062fe644d0
kernel: [490894.231982]  0000000000015b80 0000000000015b80 ffff88063174bfd8 0000000000015b80
kernel: [490894.232033] Call Trace:
kernel: [490894.232059]  [<ffffffff8117fce0>] ? sync_buffer+0x0/0x50
kernel: [490894.232089]  [<ffffffff815a1f13>] io_schedule+0x73/0xc0
kernel: [490894.232115]  [<ffffffff8117fd25>] sync_buffer+0x45/0x50
kernel: [490894.232143]  [<ffffffff815a258f>] __wait_on_bit+0x5f/0x90
kernel: [490894.232170]  [<ffffffff8117fce0>] ? sync_buffer+0x0/0x50
kernel: [490894.232197]  [<ffffffff815a2638>] out_of_line_wait_on_bit+0x78/0x90
kernel: [490894.232227]  [<ffffffff81080250>] ? wake_bit_function+0x0/0x40
kernel: [490894.232255]  [<ffffffff8117fcd6>] __wait_on_buffer+0x26/0x30
kernel: [490894.232288]  [<ffffffffa00131be>] squashfs_read_data+0x1be/0x520 [squashfs]
kernel: [490894.232320]  [<ffffffff8114f0f1>] ? __mem_cgroup_try_charge+0x71/0x450
kernel: [490894.232350]  [<ffffffffa0013963>] squashfs_cache_get+0x1c3/0x320 [squashfs]
kernel: [490894.232381]  [<ffffffffa00136eb>] ? squashfs_copy_data+0x10b/0x130 [squashfs]
kernel: [490894.232426]  [<ffffffff815a3dbe>] ? _raw_spin_lock+0xe/0x20
kernel: [490894.232454]  [<ffffffffa0013b68>] ? squashfs_read_metadata+0x48/0xf0 [squashfs]
kernel: [490894.232499]  [<ffffffffa0013ae1>] squashfs_get_datablock+0x21/0x30 [squashfs]
kernel: [490894.232544]  [<ffffffffa0015026>] squashfs_readpage+0x436/0x4a0 [squashfs]
kernel: [490894.232575]  [<ffffffff8111a375>] ? __inc_zone_page_state+0x35/0x40
kernel: [490894.232606]  [<ffffffff8110d072>] __do_page_cache_readahead+0x172/0x210
kernel: [490894.232636]  [<ffffffff8110d131>] ra_submit+0x21/0x30
kernel: [490894.232662]  [<ffffffff811045f3>] filemap_fault+0x3f3/0x450
kernel: [490894.232691]  [<ffffffff812bd156>] ? prio_tree_insert+0x256/0x2b0
kernel: [490894.232726]  [<ffffffffa009225d>] aufs_fault+0x11d/0x170 [aufs]
kernel: [490894.232755]  [<ffffffff8111f6d4>] __do_fault+0x54/0x560
kernel: [490894.232782]  [<ffffffff81122f39>] handle_mm_fault+0x1b9/0x440
kernel: [490894.232811]  [<ffffffff811286f5>] ? do_mmap_pgoff+0x335/0x380
kernel: [490894.232840]  [<ffffffff815a7af5>] do_page_fault+0x125/0x350
kernel: [490894.232867]  [<ffffffff815a4675>] page_fault+0x25/0x30

Os info

cat /etc/issue.net 
Ubuntu 10.04.2 LTS

uname -a
Linux Shard1Host3 2.6.35-32-server #68~lucid1-Ubuntu SMP Wed Mar 28 18:33:00 UTC 2012 x86_64 GNU/Linux

This system load via ltsp and hasn't harddrives also it has a lot of memory 24Gb.

free -m
             total       used       free     shared    buffers     cached
Mem:         24152      17090       7061          0         50        494
-/+ buffers/cache:      16545       7607
Swap:            0          0          0

I put vmstat info here but I think it won't give results after reboot

vmstat 1 30
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0      0 7231156  52196 506400    0    0     0     0  172  143  7  0 92  0
 1  0      0 7231024  52196 506400    0    0     0     0 7859 16233  5  0 94  0
 0  0      0 7231024  52196 506400    0    0     0     0 7870 16446  2  0 98  0
 0  0      0 7230900  52196 506400    0    0     0     0 7308 15661  5  0 95  0
 0  0      0 7231100  52196 506400    0    0     0     0 7960 16543  6  0 94  0
 0  0      0 7231100  52196 506400    0    0     0     0 7542 16047  5  1 94  0
 3  0      0 7231100  52196 506400    0    0     0     0 7709 16621  3  0 96  0
 0  0      0 7231220  52196 506400    0    0     0     0 7857 16552  4  0 96  0
 0  0      0 7231220  52196 506400    0    0     0     0 7192 15491  6  0 94  0
 0  0      0 7231220  52196 506400    0    0     0     0 7423 15792  5  1 94  0
 1  0      0 7231260  52196 506404    0    0     0     0 7686 16296  2  0 98  0
 0  0      0 7231260  52196 506404    0    0     0     0 6976 15183  5  0 95  0
 0  0      0 7231260  52196 506404    0    0     0     0 7303 15600  4  0 95  0
 0  0      0 7231320  52196 506404    0    0     0     0 7967 16241  1  0 98  0
 0  0      0 7231444  52196 506404    0    0     0     0 6948 15113  6  0 94  0
 0  0      0 7231444  52196 506404    0    0     0     0 7931 16181  6  0 94  0
 1  0      0 7231516  52196 506404    0    0     0     0 7715 15829  6  0 94  0
 0  0      0 7231516  52196 506404    0    0     0     0 7771 16036  2  0 97  0
 0  0      0 7231268  52196 506404    0    0     0     0 7782 16202  6  0 94  0
 1  0      0 7231212  52196 506404    0    0     0     0 7457 15622  4  0 96  0
 0  0      0 7231212  52196 506404    0    0     0     0 7573 16045  2  0 98  0
 2  0      0 7231216  52196 506404    0    0     0     0 7689 16076  6  0 94  0
 0  0      0 7231424  52196 506404    0    0     0     0 7429 15650  4  0 95  0
 3  0      0 7231424  52196 506404    0    0     0     0 7534 16168  3  0 97  0
 1  0      0 7230548  52196 506404    0    0     0     0 8559 15926  7  1 92  0
 0  0      0 7230672  52196 506404    0    0     0     0 7720 15905  2  0 98  0
 0  0      0 7230548  52196 506404    0    0     0     0 7677 16313  5  0 95  0
 1  0      0 7230676  52196 506404    0    0     0     0 7209 15432  5  0 95  0
 0  0      0 7230800  52196 506404    0    0     0     0 7522 15861  2  0 98  0
 0  0      0 7230552  52196 506404    0    0     0     0 7760 16661  5  0 95  0

In the munin(monitoring system) graphs I see(before server hung): Disk(nbd0) IOs per device:

read: 289m but avg by week 2.09m

Disk(nbd0) throughput per device:

read: 4.73k but avg by week 108.76

Disk(nbd0) utilization per device:

100% but avg by week 1.2%

Eth0 traffic was low:

in/out only 2Mbps

Number of threads increased to 566 usually 392

Fork rate 1.08 but usually 2.82

VMStat(processes state)

Increased to 17.77(from 0 as far as I could see in the graph)

CPU usage

iowait 880.46% when usually 6.67%

It'll be great if somebody help me to understand what's up.

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2 Answers 2

From your stack trace, we can see that the kernel hit a page fault and then tried to read some data from your squashfs, at which point it got hung for 120 seconds (or more). This suggests that something is wrong with the flash drive, DVD or whatever media from which you're booting the system. You were not at all specific about this, so you'll have to look at whichever device has a squashfs filesystem on it.

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I wrote about that. I said that this is LTSP image. It loaded via network from tftp. BTW image is fine, another 10 servers work successfully, image is stable. I want to replace network card and check what result will be. Also i set monitoring for processes with state D and monitor lsof of this processes. –  alterpub Dec 11 '12 at 17:56
up vote 0 down vote accepted

Solution: 1) changed network card 2) changed NFSv3 to NFSv4 Now, all is ok. I think that issue was with network card.

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