linux-kernel - Re: Debugging system freezes on filesystem writes

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Message-ID: <5124B613.6040400@hibox.fi>
Date:	Wed, 20 Feb 2013 13:40:03 +0200
From:	Marcus Sundman <marcus@...ox.fi>
To:	Jan Kara <jack@...e.cz>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Debugging system freezes on filesystem writes

On 20.02.2013 10:42, Marcus Sundman wrote:
> On 05.12.2012 17:32, Jan Kara wrote:
>>    I see. Maybe you could have something like
>> while true; do echo w >/proc/sysrq-trigger; sleep 10; done
>>    running in the background?
>
> Sure, but I suspect it'll take until the worst is over before it 
> manages to load and execute that "echo w".

Here is a big run of sysrq-triggering, all while I was uncompressing a 
big rar file causing the whole system to be utterly unusable.
NB: Even with realtime I/O-priority the sysrq couldn't be triggered 
between 12:41:54 and 12:42:49, as you can see from the dmesg-3.txt file.

$ sudo ionice -c 1 su
# ionice
realtime: prio 4
# while true; do sleep 10; echo w >/proc/sysrq-trigger; done
^C
# tail -n +1700 /var/log/syslog >dmesg-3.txt

http://sundman.iki.fi/dmesg-3.txt


Regards,
Marcus
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