linux-kernel - Re: possible regression in kernel 3.6 and 3.7-rc: system hangs during nightly tape backup

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Date:	Wed, 05 Dec 2012 12:03:51 +0100
From:	Tilman Schmidt <tilman@...p.cc>
To:	LKML <linux-kernel@...r.kernel.org>,
	Linux IDE <linux-ide@...r.kernel.org>
Subject: Re: possible regression in kernel 3.6 and 3.7-rc: system hangs during
 nightly tape backup

Problem still exists in kernel 3.7-rc7.

During the second backup run after I booted kernel 3.7.0-rc7, once
again all disk activity suddenly ceased, dmesg started to report
tasks "hung for more than 120 seconds", and everything happening
after that was forgotten after a reboot.

Can I do anything to help hunting this down?

Am 20.11.2012 01:14, schrieb Tilman Schmidt:
> For the 4th time now after switching to kernel 3.6, my system became
> unresponsive during the nightly Bacula backup run. It looks as if
> all disk accesses are suddenly blocked:
> - Desktop apps stop responding one after another, starting with
>   Firefox followed by other "heavy" apps, while Konsole windows
>   continue being usable for a while.
> - "top" shows the load average steadily increasing with no process
>   actually consuming relevant quantities of CPU.
> - I can do "dmesg > /root/dmesg.out" followed by "less /root/dmesg.out"
>   in a Konsole window just fine, but after the inevitable hard reset
>   the file /root/dmesg.out isn't there.
> - The "sync" command hangs indefinitely.
> - The "shutdown" command and ctrl/alt/Del emit "system going down"
>   broadcast messages but never get anywhere.
> - Killing processes manually works for some (bacula-sd even ejects
>   the tape before exiting) but most remain in state D or Z.
> - Eventually, all text consoles are blocked and a hardware reset is
>   the only remaining option.
> - After the reboot, a Bacula spool file is left behind in
>   /var/spool/bacula, proof that the hang happened during the backup.
> 
> This does not happen during every backup run, but frequently enough
> to be annoying. (About once per week.) It never happened with kernel
> 3.5. For comparison went back to kernel 3.5.7 for a week and it
> never happened during that time. Last night I booted 3.6.7 and the
> very next backup caused the hang again. The last kernel message that
> made it to the syslog on disk was
> 
> Nov 19 23:05:04 xenon kernel: [73877.128546] st0: Block limits 256 -
> 524288 bytes.
> 
> triggered by the start of the backup. In dmesg the next message was
> 
> [74401.249091] INFO: task flush-253:2:1320 blocked for more than 120
> seconds.
> 
> followed by a backtrace. I have photos of the remaining dmesg output
> which I'll try to upload somewhere accessible tomorrow.
> 
> Hardware configuration:
> Intel Pentium D, Intel DQ965GF mainboard, 6 GB RAM
> onboard S-ATA controller driving two 500 GB S-ATA disks
> and a Pioneer DVR-216D DVD-RW drive
> Adaptec 29160B Ultra160 SCSI adapter driving a
> Tandberg TS400 LTO-2 tape drive
> 
> Disk configuration: md RAID1, LVM, ext3 and ext4 volumes
> 
> Software: Opensuse 11.4 64 bit, vanilla kernel 3.5.7 and 3.6.7,
> Bacula 5.2.12
> 
> HTH
> T.
> 


-- 
Tilman Schmidt                    E-Mail: tilman@...p.cc
Bonn, Germany
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