linux-kernel - Re: Strange system hangs

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Date:	Fri, 28 Sep 2007 11:44:43 +0200 (CEST)
From:	Krzysztof Oledzki <olel@....pl>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Strange system hangs



On Fri, 28 Sep 2007, Peter Zijlstra wrote:

> On Fri, 2007-09-28 at 10:42 +0200, Krzysztof Oledzki wrote:
>> Hello,
>>
>> I am experiencing weird system hangs. Once about 2-5 weeks system freezes
>> and stops accepting remote connections, so it is no longer possible to
>> connect to most important services: smtp (postfix), www (squid) or even
>> ssh. Such connection is accepted but then it hangs.
>>
>> What is strange, that previously established ssh session is usable. It is
>> possible to work on such system until you do something stupid like "less
>> /var/log/all.log".
>
> So it takes weeks to reproduce this?

Unfortunately, yes. :(

>>                           free                        sibling
>>    task             PC    stack   pid father child younger older
>> syslogd       D F5C83C60     0  2162      1 (NOTLB)
>>         f5c83c74 00000082 00000002 f5c83c60 f5c83c5c 00000000 00000000 78538d20
>>         00000009 00000001 f7f6a070 f7cb8030 82c47e5f 0001cfed 00000a43 f7f6a17c
>>         7a016980 f705dc80 78404217 7812c708 00000000 00000213 f5c83c84 1e7a64bb
>> Call Trace:
>>   [<78404217>] _spin_unlock_irqrestore+0xf/0x23
>>   [<7812c708>] __mod_timer+0x92/0x9c
>>   [<78402b34>] schedule_timeout+0x70/0x8d
>>   [<7812c521>] process_timeout+0x0/0x5
>>   [<78402548>] io_schedule_timeout+0x1e/0x28
>>   [<7814d41e>] congestion_wait+0x50/0x64
>>   [<78134abc>] autoremove_wake_function+0x0/0x35
>>   [<781493e7>] balance_dirty_pages_ratelimited_nr+0x16e/0x1dc
>>   [<78145bd0>] generic_file_buffered_write+0x4ee/0x605
>>   [<783c55a1>] unix_dgram_recvmsg+0x1b4/0x1c8
>>   [<78128c8e>] current_fs_time+0x41/0x46
>>   [<78146167>] __generic_file_aio_write_nolock+0x480/0x4df
>>   [<7814621b>] generic_file_aio_write+0x55/0xb3
>>   [<78194b28>] ext3_file_write+0x24/0x8f
>>   [<7815f34f>] do_sync_readv_writev+0xc1/0xfe
>>   [<78134abc>] autoremove_wake_function+0x0/0x35
>>   [<784041ae>] _spin_unlock+0xd/0x21
>>   [<781a8c38>] log_wait_commit+0xc3/0xe3
>>   [<7814448b>] find_get_pages_tag+0x76/0x80
>>   [<7815f204>] rw_copy_check_uvector+0x50/0xaa
>>   [<7815f9d4>] do_readv_writev+0x99/0x164
>>   [<78194b04>] ext3_file_write+0x0/0x8f
>>   [<7815fadc>] vfs_writev+0x3d/0x48
>>   [<7815feb5>] sys_writev+0x41/0x67
>>   [<78103d6a>] sysenter_past_esp+0x5f/0x85
>>   =======================
>
> This trace puzzles me, what is: unix_dgram_recvmsg doing there.
> Also, it has two invocations of: ext3_file_write
> do you have a stacked filesystem of sorts, ext3 on loopback on ext3?

No, no loopback:

# mount
/dev/md0 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec)
devpts on /dev/pts type devpts (rw,nosuid,noexec)
/dev/mapper/VolGrp0-usr on /usr type ext3 (rw,nodev,data=journal)
/dev/mapper/VolGrp0-var on /var type ext3 (rw,nodev,data=journal)
/dev/mapper/VolGrp0-squid_spool on /var/cache/squid/cd0 type ext3 (rw,nosuid,nodev,noatime,data=writeback)
/dev/mapper/VolGrp0-squid_spool2 on /var/cache/squid/cd1 type ext3 (rw,nosuid,nodev,noatime,data=writeback)
/dev/mapper/VolGrp0-news_spool on /var/spool/news type ext3 (rw,nosuid,nodev,noatime)
shm on /dev/shm type tmpfs (rw,noexec,nosuid,nodev)
usbfs on /proc/bus/usb type usbfs (rw,noexec,nosuid,devmode=0664,devgid=85)
owl:/usr/gentoo-nfs on /usr/gentoo-nfs type nfs (ro,nosuid,nodev,noatime,bg,intr,tcp,addr=192.168.129.26)

Nothing more.

>> freshclam     D 00000282     0  2866      1 (NOTLB)
>>         f36e3cc4 00000082 00000009 00000282 7a0173c0 00000002 00000000 0000007b
>>         00000009 00000001 f7cb8030 f7c72030 82c4884d 0001cfed 000009ee f7cb813c
>>         7a016980 f66c0b80 78404217 7812c708 00000000 00000213 f36e3cd4 1e7a64bb
>> Call Trace:
>>   [<78404217>] _spin_unlock_irqrestore+0xf/0x23
>>   [<7812c708>] __mod_timer+0x92/0x9c
>>   [<78402b34>] schedule_timeout+0x70/0x8d
>>   [<7812c521>] process_timeout+0x0/0x5
>>   [<78402548>] io_schedule_timeout+0x1e/0x28
>>   [<7814d41e>] congestion_wait+0x50/0x64
>>   [<78134abc>] autoremove_wake_function+0x0/0x35
>>   [<781493e7>] balance_dirty_pages_ratelimited_nr+0x16e/0x1dc
>>   [<78145bd0>] generic_file_buffered_write+0x4ee/0x605
>>   [<7819cdb4>] __ext3_journal_stop+0x19/0x34
>>   [<7840408f>] _spin_lock+0xd/0x5a
>>   [<78176f3d>] __mark_inode_dirty+0xdd/0x16f
>>   [<78128c8e>] current_fs_time+0x41/0x46
>>   [<78146167>] __generic_file_aio_write_nolock+0x480/0x4df
>>   [<7814621b>] generic_file_aio_write+0x55/0xb3
>>   [<78103159>] setup_sigcontext+0x105/0x189
>>   [<78194b28>] ext3_file_write+0x24/0x8f
>>   [<7815f453>] do_sync_write+0xc7/0x10a
>>   [<78134abc>] autoremove_wake_function+0x0/0x35
>>   [<781085d2>] convert_fxsr_from_user+0x15/0xd5
>>   [<7815f38c>] do_sync_write+0x0/0x10a
>>   [<7815fbb6>] vfs_write+0x8a/0x10c
>>   [<78160123>] sys_write+0x41/0x67
>>   [<78103d6a>] sysenter_past_esp+0x5f/0x85
>>   =======================
>
> single write, no networking, also stuck in balance_dirty_pages().

Exactly. Strange, isn't it?

Thanks.

Best regards,

 				Krzysztof Olędzki