Moises Silva
Senior Software Engineer
Sangoma Technologies Inc. | 100 Renfrew Drive, Suite 100, Markham ON L3R 9R6 Canada
t. 1 905 474 1990 x128 | e. moy@sangoma.com

On Sun, Nov 14, 2010 at 7:10 PM, Troy Anderson <freeswitch@tlainvestments.com> wrote:

I've been looking deeper into this, and it seems that poll() in zt_wait ftmod_zt.c is returning EINTR, which means it was interrupted by a signal while in the system call (as the error points out). After STFW for a while, the advice is to immediately call poll() again if receiving an EINTR. I would patch the code and try it, but the only place I'm experiencing this is in a busy installation, and I don't want to risk the downtime before getting some feedback as the the viability of such an approach.

In addition, I am not familiar enough with linux signals to be sure this is a good idea. Is there a way to find out what signal is interrupting the system call? That may be helpful in determining what's going on here.

Here's the patch I'm considering:

--- a/libs/freetdm/src/ftmod/ftmod_zt/ftmod_zt.c
+++ b/libs/freetdm/src/ftmod/ftmod_zt/ftmod_zt.c
@@ -885,7 +885,8 @@ static FIO_WAIT_FUNCTION(zt_wait)
memset(&pfds[0], 0, sizeof(pfds[0]));
pfds[0].fd = ftdmchan->sockfd;
pfds[0].events = inflags;
- result = poll(pfds, 1, to);
+ while ((result = poll(pfds, 1, to)) < 0 && errno == EINTR)
+ continue;
*flags = 0;

if (pfds[0].revents & POLLERR) {

Any thoughts?

Thanks,
Troy

On Nov 12, 2010, at 10:26 AM, Anthony Minessale wrote:

> sigh, another case of DAHDI issues.
>
>
> On Fri, Nov 12, 2010 at 10:25 AM, Troy Anderson
> <freeswitch@tlainvestments.com> wrote:
>> Thanks for the code change providing additional diagnostics. I finally saw another call drop, but didn't have full logging on at the time. The additional logging provided the following:
>>
>> 2010-11-12 11:12:54.906656 [ERR] ftmod_zt.c:904 [s1c23][1:23] Failed to poll DAHDI device: Interrupted system call
>> 2010-11-12 11:12:54.906656 [ERR] ftmod_zt.c:904 [s1c19][1:19] Failed to poll DAHDI device: Interrupted system call
>> 2010-11-12 11:12:54.906656 [WARNING] mod_freetdm.c:660 failed to wait for I/O
>> 2010-11-12 11:12:54.906656 [WARNING] mod_freetdm.c:660 failed to wait for I/O
>> 2010-11-12 11:12:54.906656 [ERR] ftmod_zt.c:904 [s1c20][1:20] Failed to poll DAHDI device: Interrupted system call
>> 2010-11-12 11:12:54.906656 [WARNING] mod_freetdm.c:660 failed to wait for I/O
>> 2010-11-12 11:12:54.906656 [ERR] ftmod_zt.c:904 [s1c21][1:21] Failed to poll DAHDI device: Interrupted system call
>> 2010-11-12 11:12:54.906656 [WARNING] mod_freetdm.c:660 failed to wait for I/O
>>
>> I'll turn up logging and see what shows up next time, but any ideas on what may cause this?
>>
>> Thanks!
>> Troy
>>
>> On Nov 6, 2010, at 2:17 PM, Moises Silva wrote:
>>
>>> On Fri, Nov 5, 2010 at 12:58 PM, Troy Anderson
>>> <freeswitch@tlainvestments.com> wrote:
>>>> We have an installation with a dual PRI and lots of call volume. Among many successful calls each day, we have been experiencing a one or two dropped per day, and they always coincide with a "failed to wait for I/O" warning from mod_freetdm. I have attempted to track down the root cause in the source and by poring over the logs, but cannot figure it out. I have included the redacted logs here. The log file in question is 10MB and has lots of call data that doesn't relate - I know I risked removing something important, but I tried to put in all the data related to this call.
>>>>
>>>> I appreciate any insights or advice on tracking this down.
>>>>
>>>
>>> If you update your git tree you will be able to get more information
>>> the next time it happens. I added some code to print the reason for
>>> that error to happen.
>>>
>>> Moises Silva
>>> Senior Software Engineer
>>> Sangoma Technologies Inc. | 100 Renfrew Drive, Suite 100, Markham ON
>>> L3R 9R6 Canada
>>> t. 1 905 474 1990 x128 | e. moy@sangoma.com
>>>
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>
> --
> Anthony Minessale II
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