Ok, I followed the procedure, those where the results.
The full output in syslog was the following:
Aug 19 09:14:42 <server> nagios: wproc: Core Worker 11582: job 87 (pid=13292) timed out. Killing it
Aug 19 09:14:42 <server> nagios: job 87 (pid=13292): read() returned error 11
Aug 19 09:14:42 <server> nagios: wproc: CHECK job 87 from worker Core Worker 11582 timed out after 30.00s
Aug 19 09:14:42 <server> nagios: wproc: host=voip-univesp; service=(null);
Aug 19 09:14:42 <server> nagios: wproc: early_timeout=1; exited_ok=0; wait_status=0; error_code=62;
Aug 19 09:14:42 <server> nagios: Warning: Check of host 'voip-univesp' timed out after 30.00 seconds
Aug 19 09:14:42 <server> nagios: wproc: Core Worker 11582: job 87 (pid=13292): Dormant child reaped
Then gdb gave me the following:
root@<server>:/var/log# gdb -p 11576
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <
http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<
http://www.gnu.org/software/gdb/bugs/>.
Attaching to process 11576
Reading symbols from /usr/local/nagios/bin/nagios...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libm.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libm.so.6
Reading symbols from /usr/lib/x86_64-linux-gnu/libltdl.so.7...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/x86_64-linux-gnu/libltdl.so.7
Reading symbols from /lib/x86_64-linux-gnu/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libc.so.6
Reading symbols from /lib/x86_64-linux-gnu/libdl.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libdl.so.2
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /lib/x86_64-linux-gnu/libnss_compat.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libnss_compat.so.2
Reading symbols from /lib/x86_64-linux-gnu/libnsl.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libnsl.so.1
Reading symbols from /lib/x86_64-linux-gnu/libnss_nis.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libnss_nis.so.2
Reading symbols from /lib/x86_64-linux-gnu/libnss_files.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib/x86_64-linux-gnu/libnss_files.so.2
0x00007f100b91a5f3 in epoll_wait () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0 0x00007f100b91a5f3 in epoll_wait () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x0000000000472201 in iobroker_poll ()
#2 0x0000000000433413 in event_execution_loop ()
#3 0x0000000000415c35 in main ()
Roberto