The information below is from a productive system without debugging enabled. If have extracted the following information so far: Related Threads: (gdb) thread 23 [Switching to thread 23 (Thread 0x7f39210ee700 (LWP 364))]#0 __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136 136 2: movl %edx, %eax (gdb) bt #0 __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136 #1 0x0000003974a09523 in _L_lock_892 () from /lib64/libpthread-2.12.so #2 0x0000003974a09407 in __pthread_mutex_lock (mutex=0x7f397004fb00) at pthread_mutex_lock.c:82 #3 0x00007f3925f8d92f in sip_pvt_lock_full (*pvt=0x7f397004fb60*) at chan_sip.c:9063 #4 0x00007f3925ff543f in send_provisional_keepalive_full (pvt=0x7f397004fb60, with_sdp=0) at chan_sip.c:4466 #5 0x000000000058ac9e in ast_sched_runq (*con=0x1108b10*) at sched.c:643 #6 0x00007f3925fd33d7 in do_monitor (data=) at chan_sip.c:28858 #7 0x00000000005bcd2b in dummy_start (data=) at utils.c:1232 #8 0x0000003974a079d1 in start_thread (arg=0x7f39210ee700) at pthread_create.c:301 #9 0x00000039746e88fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115 (gdb) frame 2 #2 0x0000003974a09407 in __pthread_mutex_lock (mutex=0x7f397004fb00) at pthread_mutex_lock.c:82 82 LLL_MUTEX_LOCK (mutex); (gdb) p *mutex $6 = { __data = { __lock = 2, __count = 1, __owner = *14513*, __nusers = 1, __kind = 1, __spins = 0, __list = { __prev = 0x0, __next = 0x0 } }, __size = "\002\000\000\000\001\000\000\000\261\070\000\000\001\000\000\000\001", '\000' , __align = 4294967298 } *Mutex Owner is 14513* (gdb) info threads 76 Thread 0x7f397fa7f700 (LWP 316) sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86 ... 48 Thread 0x7f3920646700 (LWP 14175) __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136 47 Thread 0x7f391fffa700 (LWP *14513*) pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:183 46 Thread 0x7f391ff02700 (LWP 14549) __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136 ... 24 Thread 0x7f3920ff6700 (LWP 366) pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:183 * 23 Thread 0x7f39210ee700 (LWP 364) __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136 22 Thread 0x7f39211e6700 (LWP 362) 0x00000039746df0d3 in __poll (fds=, nfds=, timeout=) at ../sysdeps/unix/sysv/linux/poll.c:87 ... (gdb) thread 47 [Switching to thread 47 (Thread 0x7f391fffa700 (LWP 14513))]#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:183 183 62: movl (%rsp), %edi (gdb) bt #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:183 #1 0x000000000058a9a1 in ast_sched_del (*con=0x1108b10*, id=6096) at sched.c:500 #2 0x00007f3925ff6b74 in update_provisional_keepalive (p=0x7f397004fb60, msg=, req=, with_sdp=1) at chan_sip.c:4525 #3 transmit_provisional_response (*p=0x7f397004fb60*, msg=, req=, with_sdp=1) at chan_sip.c:12375 #4 0x00007f392600d2e4 in sip_indicate (ast=0x7f397009dde0, condition=, data=0x0, datalen=0) at chan_sip.c:7708 #5 0x00000000004ae43e in ast_indicate_data (chan=0x7f397009dde0, _condition=14, data=0x0, datalen=0) at channel.c:4555 #6 0x00007f39253555bd in wait_for_answer (in=0x7f397009dde0, out_chans=0x7f391fff74e0, to=0x7f391fff751c, peerflags=0x7f391fff7560, opt_args=0x7f391fff7170, pa=0x7f391fff69a0, num_in=0x7f391fff7460, result=0x7f391fff7514, dtmf_progress=0x0, ignore_cc=1, forced_clid=0x7f391fff73e0, stored_clid=0x7f391fff7390) at app_dial.c:1374 #7 0x00007f392535a134 in dial_exec_full (chan=, data=, peerflags=0x7f391fff7560, continue_exec=0x0) at app_dial.c:2680 #8 0x00007f392535bff6 in dial_exec (chan=, data=) at app_dial.c:3133 #9 0x0000000000551f15 in pbx_exec (c=0x7f397009dde0, app=0x115e9b0, data=0x7f391fff76c0 "DAHDI/g1/00963932263976") at pbx.c:1662 #10 0x000000000055beb2 in pbx_extension_helper (c=0x7f397009dde0, con=0x0, context=0x7f397009e798 "moonstar", exten=0x7f397009e7e8 "+963932263976", priority=7, label=0x0, callerid=0x7f396402f9a0 "905388446334", action=E_SPAWN, found=0x7f391fff9c9c, combined_find_spawn=1) at pbx.c:4934 #11 0x0000000000562655 in ast_spawn_extension (c=0x7f397009dde0, args=0x0) at pbx.c:5967 #12 __ast_pbx_run (c=0x7f397009dde0, args=0x0) at pbx.c:6381 #13 0x0000000000563d1b in pbx_thread (data=) at pbx.c:6701 #14 0x00000000005bcd2b in dummy_start (data=) at utils.c:1232 #15 0x0000003974a079d1 in start_thread (arg=0x7f391fffa700) at pthread_create.c:301 #16 0x00000039746e88fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115 (gdb) frame 1 #1 0x000000000058a9a1 in ast_sched_del (*con=0x1108b10*, id=6096) at sched.c:500 500 ast_cond_wait(&s->cond, &con->lock); (gdb) p con $1 = (struct ast_sched_context *) 0x1108b10 (gdb) l 495 s = con->currently_executing; 496 s->deleted = 1; 497 /* Wait for executing task to complete so that caller of ast_sched_del() does not 498 * free memory out from under the task. 499 */ 500 ast_cond_wait(&s->cond, &con->lock); 501 /* Do not sched_release() here because ast_sched_runq() will do it */ 502 } 503 504 #ifdef DUMP_SCHEDULER