can I bring Linux down by running "renice -20 cpu_intensive_process"?
From: Tomasz Chmielewski
Date: Fri Mar 10 2006 - 08:34:26 EST
I have a Linux server (kernel 2.6.8.1 + Linux RAID1) which is a "backup"
machine: it gets the files from other servers, compresses it, writes to
the tape, checks md5sums etc.
It's been running for quite a bit, no problems with stability so far.
Yesterday, something happened though.
I was logged in remotely, and the system was running md5sum against a 30
GB file.
I wanted the things to speed up a bit, and made "renice -20 <md5sum_pid>".
Few minutes after that I couldn't start any process, so I thought I made
the system so busy with renice -20, that my SSH session probably
disconnected.
In the morning, the system was still unavailable - I could ping it, I
could telnet to any of the ports opened, but nothing more happened.
SSH was waiting forever after:
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_dsa type -1
Nothing was displayed on the monitor (all black).
As I restarted the machine, I saw that the logging ends few minutes
after I changed the priority of md5sum to -20.
So here is my question: is it possible to bring down the machine by
simply doing "renice -20 cpu_intensive_process"?
As I said, this machine does heavy compression and md5sum calculations
of big files every day, and was stable all the time - but stopped
responding after I changed the priority of a CPU-intensive process to -20.
Coincidence and a hardware failure?
--
Tomasz Chmielewski
http://wpkg.org
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