[asterisk-bugs] [DAHDI-linux 0013930]: dahdi_dummy does not tick on some systems

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13930 
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Reported By:                tzafrir
Assigned To:                sruffell
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Project:                    DAHDI-linux
Issue ID:                   13930
Category:                   dahdi_dummy
Reproducibility:            sometimes
Severity:                   minor
Priority:                   normal
Status:                     ready for testing
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Date Submitted:             2008-11-19 08:34 CST
Last Modified:              2009-03-30 10:43 CDT
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Summary:                    dahdi_dummy does not tick on some systems
Description: 
On some systems dahdi_dummy (or ztdummy, in the case of Zaptel) fails to
"tick" DAHDI and hence DAHDI does not provide a working timing source.

Indications that DAHDI (Zaptel) provides no timing source:

1. dahdi_test (zttest) does not give an error on startup, but hangs.
2. Asterisk >= 1.4.20 fails to start, and gives the ugly "no timing
source" error message:

ERROR[10981]: asterisk.c:3036 main: Asterisk has detected a problem
with your DAHDI configuration and will shutdown for your protection.
You have options:
        1. You only have to compile DAHDI support into Asterisk if you
need it.  One option is to recompile without DAHDI support.
        2. You only have to load DAHDI drivers if you want to take
advantage of DAHDI services.  One option is to unload DAHDI modules if
you don't need them.
        3. If you need DAHDI services, you must correctly configure
DAHDI.

An indication that dahdi_dummy should be the timing source for dahdi could
be:

  lsmod | grep ^dahdi
  dahdi                 231888  1 dahdi_dummy

Or to see that /proc/dahdi/1 is dahdi_dummy and is listed as "MASTER".


I have seen various suggestions on how to solve this. None seems to be a
silver bullet. 
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---------------------------------------------------------------------- 
 (0102394) sruffell (administrator) - 2009-03-30 10:43
 http://bugs.digium.com/view.php?id=13930#c102394 
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On a poweredge 2600 (with a super long system management interrupt) with
CentOS 5.2 and kernel version 2.6.18-92.1.22.el5, I ran the timertest from
dahdi-tools with a dahdi_dummy in three configurations.

With USE_RTC commented out, timer test was off by 118ms after running for
97 seconds.
Timer Expired (97118 ms)!

Using the RTC on this system was better, as it was off 57ms after running
for 15 minutes.
Timer Expired (925057 ms)!

Using no_dahdi_dummy_rtc-3.patch, it was off 38ms after running for 22
hours.
Timer Expired (81369038 ms)! 

Issue History 
Date Modified    Username       Field                    Change               
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2009-03-30 10:43 sruffell       Note Added: 0102394                          
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