I got two such stuck legs right now. Here are their threads.
Thread 45 (Thread 0x7f3f574fb940 (LWP 25467)):
#0 0x0000003d8d207c65 in pthread_join () from /lib64/libpthread.so.0
#1 0x00007f3f712b9db9 in apr_thread_join () from /usr/local/freeswitch/lib/libfreeswitch.so.1
#2 0x00007f3f71186d2c in switch_thread_join (retval=0x7f3f574fa0fc, thd=0x7f3f683f8cb8) at src/switch_apr.c:1171
#3 0x00007f3f667b233c in conference_loop_output (member=0x7f3f574fa540) at mod_conference.c:4481
#4 0x00007f3f667c1a4c in conference_function (session=0x7f3f503a8b48, data=0x7f3f681cbd10 "5d7b86e0-3ea5-11e4-b722-1231393fb01c@default+flags{join-only}") at mod_conference.c:8695
#5 0x00007f3f711c23e7 in switch_core_session_exec (session=0x7f3f503a8b48, application_interface=0x7f3f600e1920, arg=0x7f3f681cbd10 "5d7b86e0-3ea5-11e4-b722-1231393fb01c@default+flags{join-only}")
at src/switch_core_session.c:2862
#6 0x00007f3f711c1c85 in switch_core_session_execute_application_get_flags (session=0x7f3f503a8b48, app=0x7f3f681cbd00 "conference",
arg=0x7f3f681cbd10 "5d7b86e0-3ea5-11e4-b722-1231393fb01c@default+flags{join-only}", flags=0x0) at src/switch_core_session.c:2737
#7 0x00007f3f711c3c3c in switch_core_standard_on_execute (session=0x7f3f503a8b48) at src/switch_core_state_machine.c:281
#8 0x00007f3f711c4de0 in switch_core_session_run (session=0x7f3f503a8b48) at src/switch_core_state_machine.c:530
#9 0x00007f3f711be45c in switch_core_session_thread (thread=0x7f3f50b9f990, obj=0x7f3f503a8b48) at src/switch_core_session.c:1597
#10 0x00007f3f711be913 in switch_core_session_thread_pool_worker (thread=0x7f3f50b9f990, obj=0x7f3f50b9f820) at src/switch_core_session.c:1689
#11 0x00007f3f712b9b7d in dummy_worker () from /usr/local/freeswitch/lib/libfreeswitch.so.1
#12 0x0000003d8d20683d in start_thread () from /lib64/libpthread.so.0
#13 0x0000003d8cad4f8d in clone () from /lib64/libc.so.6
Thread 60 (Thread 0x7f3f575af940 (LWP 28590)):
#0 0x0000003d8d207c65 in pthread_join () from /lib64/libpthread.so.0
#1 0x00007f3f712b9db9 in apr_thread_join () from /usr/local/freeswitch/lib/libfreeswitch.so.1
#2 0x00007f3f71186d2c in switch_thread_join (retval=0x7f3f575ae0fc, thd=0x215a358) at src/switch_apr.c:1171
#3 0x00007f3f667b233c in conference_loop_output (member=0x7f3f575ae540) at mod_conference.c:4481
#4 0x00007f3f667c1a4c in conference_function (session=0x7f3f50087998, data=0x2152a38 "2e42aba0-430b-11e4-bc8b-22000a1cca7e@default+flags{join-only}") at mod_conference.c:8695
#5 0x00007f3f711c23e7 in switch_core_session_exec (session=0x7f3f50087998, application_interface=0x7f3f600e1920, arg=0x2152a38 "2e42aba0-430b-11e4-bc8b-22000a1cca7e@default+flags{join-only}")
at src/switch_core_session.c:2862
#6 0x00007f3f711c1c85 in switch_core_session_execute_application_get_flags (session=0x7f3f50087998, app=0x2152a28 "conference", arg=0x2152a38 "2e42aba0-430b-11e4-bc8b-22000a1cca7e@default+flags{join-only}",
flags=0x0) at src/switch_core_session.c:2737
#7 0x00007f3f711c3c3c in switch_core_standard_on_execute (session=0x7f3f50087998) at src/switch_core_state_machine.c:281
#8 0x00007f3f711c4de0 in switch_core_session_run (session=0x7f3f50087998) at src/switch_core_state_machine.c:530
#9 0x00007f3f711be45c in switch_core_session_thread (thread=0x214d4b0, obj=0x7f3f50087998) at src/switch_core_session.c:1597
#10 0x00007f3f711be913 in switch_core_session_thread_pool_worker (thread=0x214d4b0, obj=0x214d340) at src/switch_core_session.c:1689
#11 0x00007f3f712b9b7d in dummy_worker () from /usr/local/freeswitch/lib/libfreeswitch.so.1
#12 0x0000003d8d20683d in start_thread () from /lib64/libpthread.so.0
#13 0x0000003d8cad4f8d in clone () from /lib64/libc.so.6