[asterisk-users] kernel: dahdi: Detected time shift.

[Shaun Ruffell]

On 11/24/2010 11:02 AM, Shaun Ruffell wrote:
> On 11/24/2010 10:43 AM, Jonas Kellens wrote:
>> The only thing I have is a high level of mentionning of "kernel: dahdi:
>> Detected time shift." in /var/log/messages.
>>
>>
>> What is causing this kernel message ? Could this be the cause of the
>> server freeze ?
>>
> 
> When a system does not have a hardware device installed DAHDI uses the
> system time in order to approximate a telephony clock source (what was
> previously referred to as dahdi_dummy).  Since it uses the system time
> to accomplish this, if there is a large gap in the time (typically
> because NTP is adjusting the time) DAHDI just reports that it thinks
> it's very far behind or ahead of where it should be, and doesn't even
> try to "mix" any audio for that interval.
> 
> So, I think the "detected time shift" is more a symptom of something
> else causing locks as opposed to the source.
> 
> Is your server keeping accurate wall-time?
> 

Another case where I regularly see "detected time shift" is when I'm
running DAHDI in a virtual machine and go through a suspend / resume
cycle.  On resume when the system clock is updated DAHDI will notice the
shift.

-- 
Shaun Ruffell
Digium, Inc. | Linux Kernel Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: www.digium.com & www.asterisk.org