(gdb) bt
#0  0xb7fbbce4 in pthread_mutex_lock () from /lib/tls/libpthread.so.0
#1  0xa7a27849 in sip_fixup (oldchan=0x9d3d7178, newchan=0x9d3d7178)
    at chan_sip.c:1843
#2  0x080617e3 in ast_do_masquerade (original=0x9d3d7178) at channel.c:2387
#3  0x0805e188 in ast_read (chan=0x9d3d7178) at channel.c:1211
#4  0x08062979 in ast_channel_bridge (c0=0x9d3d7178, c1=0x81d51b0,
    config=0x915ed550, fo=0x915ecfb8, rc=0x915ecfb4) at channel.c:2699
#5  0xb1b747d7 in ast_bridge_call (chan=0x9d3d7178, peer=0x81d51b0,
    config=0x915ed550) at res_features.c:360
#6  0xa386ef29 in dial_exec (chan=0x9d3d7178, data=0x915edbea)
    at app_dial.c:1141
#7  0x080787c7 in pbx_exec (c=0x9d3d7178, app=0x81a18a8, data=0x915edbea,
    newstack=1) at pbx.c:475
#8  0xb1b7de64 in handle_exec (chan=0x9d3d7178, agi=0x915ee440, argc=3,
    argv=0x915ed9a0) at res_agi.c:918
#9  0xb1b7ef8c in agi_handle_command (chan=0x9d3d7178, agi=0x915ee440,
    buf=0x915edbe0 "EXEC") at res_agi.c:1601
#10 0xb1b7f32f in run_agi (chan=0x9d3d7178,
    request=0x915ee470 "ExtensionDial.agi", agi=0x915ee440, pid=11424, dead=0)
    at res_agi.c:1681
#11 0xb1b7f9ef in agi_exec_full (chan=0x9d3d7178, data=0x915f1000, enhanced=0,
    dead=0) at res_agi.c:1820
#12 0xb1b7fb4b in agi_exec (chan=0x9d3d7178, data=0x915f1000) at res_agi.c:1833
#13 0x080787c7 in pbx_exec (c=0x9d3d7178, app=0x80fa2d0, data=0x915f1000,
    newstack=1) at pbx.c:475
#14 0x0807ae42 in pbx_extension_helper (c=0x9d3d7178, con=0x0,
    context=0x9d3d72c4 "macro-extdial", exten=0x9d3d73b8 "s", priority=3,
    label=0x0, callerid=0xa15fcf18 "2020", action=1) at pbx.c:1275
#15 0x0807c0f2 in ast_spawn_extension (c=0x9d3d7178,
    context=0x9d3d72c4 "macro-extdial", exten=0x9d3d73b8 "s", priority=3,
    callerid=0xa15fcf18 "2020") at pbx.c:1819
#16 0xa388a357 in macro_exec (chan=0x9d3d7178, data=0x915f57c0)
    at app_macro.c:153
#17 0x080787c7 in pbx_exec (c=0x9d3d7178, app=0x819fea0, data=0x915f57c0,
    newstack=1) at pbx.c:475
#18 0x0807ae42 in pbx_extension_helper (c=0x9d3d7178, con=0x0,
    context=0x9d3d72c4 "macro-extdial", exten=0x9d3d73b8 "s", priority=1,
    label=0x0, callerid=0xa15fcf18 "2020", action=1) at pbx.c:1275
#19 0x0807c0f2 in ast_spawn_extension (c=0x9d3d7178,
    context=0x9d3d72c4 "macro-extdial", exten=0x9d3d73b8 "s", priority=1,
    callerid=0xa15fcf18 "2020") at pbx.c:1819
#20 0x0807c511 in ast_pbx_run (c=0x9d3d7178) at pbx.c:1881
#21 0x0807d0ac in pbx_thread (data=0x9d3d7178) at pbx.c:2064
#22 0xb7fb998c in start_thread () from /lib/tls/libpthread.so.0
#23 0xb7eaa7da in clone () from /lib/tls/libc.so.6