(gdb) bt
#0  0x0000003b7a808913 in pthread_mutex_trylock () from /lib64/libpthread.so.0
#1  0x00002aaabe55abb9 in ast_mutex_trylock (pmutex=0xe9) at /usr/src/asterisk-1.4.26/include/asterisk/lock.h:763
#2  0x00002aaabe55aaf3 in local_queue_frame (p=0x1bae310, isoutbound=0, f=0x459a4530, us=0x1c6c6e0, us_locked=1) at chan_local.c:184
#3  0x00002aaabe55b2ff in local_indicate (ast=0x1c6c6e0, condition=18, data=0x0, datalen=0) at chan_local.c:385
#4  0x00000000004420d7 in ast_indicate_data (chan=0x1c6c6e0, _condition=18, data=0x0, datalen=0) at channel.c:2575
#5  0x0000000000441fbb in ast_indicate (chan=0x1c6c6e0, condition=18) at channel.c:2520
#6  0x00002aaab9ca4593 in process_incoming (member=0x1f1dea0, conf=0x1c12030, f=0x2aaab4082ae0) at member.c:142
#7  0x00002aaab9ca577e in member_exec (chan=0x2aaac4041620, data=0x459a69b0) at member.c:730
#8  0x00002aaab9c9f4eb in app_conference_main (chan=0x2aaac4041620, data=0x459a69b0) at app_conference.c:67
#9  0x0000000000481f0c in pbx_exec (c=0x2aaac4041620, app=0x1b674b0, data=0x459a69b0) at pbx.c:536
#10 0x0000000000485747 in pbx_extension_helper (c=0x2aaac4041620, con=0x0, context=0x2aaac4041870 "acd_conference_record", exten=0x2aaac40418c0 "60596", priority=5, label=0x0, callerid=0x2aaac4062540 "+19513231612", action=E_SPAWN) at pbx.c:1863
#11 0x00000000004867b7 in ast_spawn_extension (c=0x2aaac4041620, context=0x2aaac4041870 "acd_conference_record", exten=0x2aaac40418c0 "60596", priority=5, callerid=0x2aaac4062540 "+19513231612") at pbx.c:2283
#12 0x0000000000486c2f in __ast_pbx_run (c=0x2aaac4041620) at pbx.c:2373
#13 0x0000000000487c7e in pbx_thread (data=0x2aaac4041620) at pbx.c:2599
#14 0x00000000004ca736 in dummy_start (data=0x2aaac40cc910) at utils.c:856
#15 0x0000003b7a806367 in start_thread () from /lib64/libpthread.so.0
#16 0x0000003b7a0d309d in clone () from /lib64/libc.so.6