[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:              2009-03-28 15:40 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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 (0102327) sruffell (administrator) - 2009-03-28 15:40
 http://bugs.digium.com/view.php?id=13930#c102327 
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This patch doesn't make any assumptions about the HZ.  It will run if HZ is
even lower than 100.  

And running the interval every 4ms is good enough I believe.  dahdi_dummy
is used when there isn't another span from which to derive timing. 
Therefore, it is used to mix channels from user space, which is typically
dealing with 20ms audio chunks.  Therefore mixing those channels every 4ms
is still a little overkill.  But at least this will still allow the
processor to stay idle longer if there aren't any channels to mix. 
Probably should be configured to run every HZ/100 (or every 10ms) for even
more potential power savings / performance improvements. 

Issue History 
Date Modified    Username       Field                    Change               
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2009-03-28 15:40 sruffell       Note Added: 0102327                          
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