[SR-Dev] [Fwd: [Kamailio-Devel] race condition]

[Klaus Darilion]

Daniel-Constantin Mierla schrieb:
> Hello,
> 
> On 04/23/2009 11:51 AM, Klaus Darilion wrote:
>> Hi guys!
>>
>> In Kamilio we had (have?) the problem described here. Maybe the 
>> problem still applies to ser-tm too, then it needs this fix too.
>>   
> this was discussed some months ago, also with SR. SR has a completely 
> different locking/synchronization system and the issue does not apply.

even better :-)

> Cheers,
> Daniel
> 
>> regards
>> klaus
>>
>> -------- Original-Nachricht --------
>> Betreff: [Kamailio-Devel] race condition
>> Datum: Thu, 23 Apr 2009 10:34:26 +0200
>> Von: Zappasodi Daniele <Daniele.Zappasodi at seltatel.it>
>> An: <devel at lists.kamailio.org>
>> Referenzen: <mailman.9.1240394401.8388.devel at lists.kamailio.org>
>>
>>
>> Hello,
>> I have a problem with a race condition with the reply and retransmission.
>> Sometimes Openser (I'm still working with 1.3.x version) ignores the 
>> provisional reply and tears down the call after the fr_timer.
>> This happens only in a particulary conditions:
>> I have a short value for fr_timer (5 sec);
>> the reply arrives very fast (I have gateway and proxy on the same box).
>>
>> In this situation can happen that a child sends the INVITE 
>> (SEND_BUFFER in t_forward_nonack) and it is suspended by the scheduler 
>> before it can execute start_retr.
>> Another child get the reply.
>> When the first child executes start_retr it sends immediately a 
>> retransmission for the INVITE and after 5 seconds (the fr_timer) it 
>> tears down the call with CANCEL, because it ignores the reply.
>>
>> I know that this is a very improbable condition (even if I encountered 
>> it), but if you want to fix it, it should be easy to solve: in 
>> t_forward_nonack, before start_retr, it should be tested if another 
>> child has already received a reply.
>> Something like this (t_fwd.c on head):
>>
>> @@ -719,7 +719,10 @@
>>                                          -p_msg->REQ_METHOD);
>>                          }
>>
>> -                       start_retr( &t->uac[i].request );
>> +                       if(p_msg->REQ_METHOD==METHOD_INVITE && 
>> t->uac[i].last_received>=100)
>> +                               LM_DBG("Last received 
>> %d\n",t->uac[i].last_received);
>> +                       else
>> +                               start_retr( &t->uac[i].request );
>>                          set_kr(REQ_FWDED);
>>                  }
>>          }
>>
>>
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>>   
>