How to diagnose system freezes?

[Mark Saad]

On Jul 31, 2012, at 8:29 PM, Julian Elischer <julian at freebsd.org> wrote:

> On 7/31/12 5:02 PM, Yuri wrote:
>> One of my 9.1-BETA1 systems periodically freezes. If sound was playing, it would usually cycle with a very short period. And system stops being sensitive to keyboard/mouse. Also ping of this system doesn't get a response.
>> I would normally think that this is the faulty memory. But memory was recently replaced and tested with memtest+ for hours both before and after freezes and it passes all tests.
>> One out of the ordinary thing that is running on this system is nvidia driver. But the freezes happen even when there is no graphics activity.
>> Another out of the ordinary thing is that the kernel is built for DTrace. But DTrace was never used in the sessions that had a freeze.
>> 
>> What is the way to diagnose this problem?
> The answer depends on a number of things but an NMI can be useful if you have some way of
> generating them. (some IPMI implementations can allw you to generate them and some motherboards have
> jumpers to allow you to attach a 'nmi-button'.
> 
> The fact that ping is not responsive is important, as that is done at a very low level but
> it may still be alive down there somewhere.
> 
> Make sure you have debugging enabled in your kernel. That will catch quite a few 'hangs'.
> 
> as also mentioned by others... a serial console and DDB may also be useful in some hangs.
> 
> 
> Julian
>> CPU: i7 CPU         920  @ 2.67GHz
>> Memory: 24GB
>> MB: P2T
>> 
>> Yuri
>> 

Yuri
  Install sysutils/mcelog and try running the example included . While not a complete definitative hardware test it can report other hardware issues that memtest86+ misses and it can be run on line in multiuser mode and via cron . 

---
Mark saad | mark.saad at longcount.org