thread apply all bt

Thread 2 (Thread 0x7f9821b0a700 (LWP 3140)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00000000004d67d1 in lwt_unix_condition_wait (condition=condition@entry=0x7c9a00 <pool_condition>, mutex=mutex@entry=0x7c99c0 <pool_mutex>) at src/unix/lwt_unix_stubs.c:263
#2  0x00000000004d6bd0 in worker_loop (data=0xce37c0) at src/unix/lwt_unix_stubs.c:1214
#3  0x00007f98229a6182 in start_thread (arg=0x7f9821b0a700) at pthread_create.c:312
#4  0x00007f98221c947d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7f9822dba740 (LWP 3139)):
#0  0x00007f98221c0da3 in select () at ../sysdeps/unix/syscall-template.S:81
#1  0x00000000004df782 in unix_select ()
#2  0x000000000044e603 in camlLwt_engine__fun_2021 () at src/unix/lwt_engine.ml:371
#3  0x000000000044e1fa in camlLwt_engine__fun_1960 () at src/unix/lwt_engine.ml:312
#4  0x000000000044fca8 in camlLwt_main__run_1018 () at src/unix/lwt_main.ml:41
#5  0x0000000000408e49 in camlMain__entry () at src/app/main.ml:168
#6  0x0000000000405169 in caml_program ()
#7  0x00000000004f376e in caml_start_program ()
#8  0x0000000000000000 in ?? ()
(gdb)