(gdb) bt
#0  0x00007f6fac3e1943 in select () from /lib64/libc.so.6
#1  0x00007f6faeeff135 in apr_sleep (t=<optimized out>) at time/unix/time.c:246
#2  0x00007f6faec35f55 in pool_thread (thread=<optimized out>, obj=<optimized out>) at src/switch_core_memory.c:569
#3  0x00007f6faeefdaf0 in dummy_worker (opaque=0x7f6faf8ddc40) at threadproc/unix/thread.c:151
#4  0x00007f6facd10dc5 in start_thread () from /lib64/libpthread.so.0
#5  0x00007f6fac3ea21d in clone () from /lib64/libc.so.6