PE2650: RH ES 4: sensors_detect freezes machine - TSC cannotbeused as a timesource

tman_dell@trejan.com tman_dell at trejan.com
Fri Jul 8 11:23:48 CDT 2005


> -----Original Message-----
> From: linux-poweredge-bounces at dell.com 
> [mailto:linux-poweredge-bounces at dell.com] On Behalf Of Robert Oschwald
> Sent: 08 July 2005 16:15
> To: linux-poweredge at dell.com
> Subject: RE: PE2650: RH ES 4: sensors_detect freezes machine 
> - TSC cannotbeused as a timesource
> 
> > sensors_detect (as part of lm_sensors) is an ugly and
> > dangerous hack. do you 
> > really intend to use lm_sensors?
> > 
> well, as it's part of RHES4, we thought it might be good to 
> get quick measures of the temp sensors. No program should 
> ever lead to a full freeze, in my opinion.

As Peter points out, it is possible to freeze the system quite easily.
sensors-detect actually probes the ISA and SMBUS buses to see if it can
find any hardware sensor chips.  I don't think Dell PowerEdges even have
compat chips.  Everything appears to be wired through the BMC and
although there is a lm_sensors driver for it, it is very basic.  If you
want to know the value of the sensors on a Dell PowerEdge then you
should install the OMSA suite which does it all for you.

The laptop which can be killed by a lm_sensors probe are Thinkpads with
a specific Atmel EEPROM chip which stores the BIOS settings.  The EEPROM
chip has a bug in it's protocol handling and the probe which should be
harmless causes it to overwrite some of the data.  This means it fails
the checksum and the laptop will totally refuse to boot.

 - Trevor



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