[Freeswitch-users] failed to wait for I/O

Sun Nov 14 17:10:25 PST 2010

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 at 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 at 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 at sangoma.com
>>> 
>>> _______________________________________________
>>> FreeSWITCH-users mailing list
>>> FreeSWITCH-users at lists.freeswitch.org
>>> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
>>> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
>>> http://www.freeswitch.org
>> 
>> 
>> _______________________________________________
>> FreeSWITCH-users mailing list
>> FreeSWITCH-users at lists.freeswitch.org
>> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
>> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
>> http://www.freeswitch.org
>> 
> 
> 
> 
> -- 
> Anthony Minessale II
> 
> FreeSWITCH http://www.freeswitch.org/
> ClueCon http://www.cluecon.com/
> Twitter: http://twitter.com/FreeSWITCH_wire
> 
> AIM: anthm
> MSN:anthony_minessale at hotmail.com
> GTALK/JABBER/PAYPAL:anthony.minessale at gmail.com
> IRC: irc.freenode.net #freeswitch
> 
> FreeSWITCH Developer Conference
> sip:888 at conference.freeswitch.org
> googletalk:conf+888 at conference.freeswitch.org
> pstn:+19193869900
> 
> _______________________________________________
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org


