[asterisk-dev] Digium card TD2400/TE40XP irq problem

Sylvain Boily sboily at proformatique.com
Fri Apr 20 06:30:14 MST 2007


I already open bug on support at digium.com and it was closed because i
send on bad support. Support says it was better to talking about this on
mailing developper. So i send you a rapport from my developper Guillaume
Knispel about some problems on zaptel. If you want access on server for
testing it was possible. We have creating a small patch just in urgence
but i was not a solution.
Unfortunatelly, We have no time now for working on this bug but it was
an important problem for all peoples who want Digium card TDM2400 and
TE40XP or B410P.
We have testing on different server with debian sarge and some other


Here is a summary of a subset of a number of defaults we encountered in
Zaptel :


First Zaptel is SMP and PREEMPT unsafe for various reasons, including
* http://bugs.digium.com/view.php?id=8422
but not only: the try_module_get mechanism is not used correctly for
driver modules, and there also are various locking and context issues
in the driver API that are not documented and really error prone (and
there are indeed errors in the way the API is used by official Zaptel
drivers themselves)


This issue is even worse :
* http://bugs.digium.com/view.php?id=8404
It's absolutely bad and broken design. There is no good reason on earth
 unconditionally busy loop for several jiffies (the way it's used in
combination with register polling for timeouting can be OK depending
statistical repartition of the wait time). Maybe there was one some time
ago but anyway this is not the case anymore if it was.


The last big issue we encountered is spin_lock_irqsave being hold for an
enormous period of time for example in wct4xxp, but as usual this kind
issue (holding spin_lock_irqsave for years) is spread all over the
tree. This just caused interrupt misses on other (including Zaptel !)
devices, resulting in a misfunction of the latter. As we needed a
setup within few minutes but the robustness, stability and functionality
were not important on this setup, I wrote a quick hack in wct4xxp which
reenabled interruptions at fixed points (patch attached), but this is
really just a hack and this approach must not be taken for a real fix.

Sylvain BOILY
Proformatique - 67 rue Voltaire - 92800 Puteaux
Tel. : 01 41 38 99 64 - Fax. : 01 41 38 99 70
Email : sboily at proformatique.com - http://proformatique.com/

"Vers un monde plus libre"
Proformatique est membre de l'ASS2L
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