(gdb) bt full
#0  0x00007f114d21cc93 in __epoll_wait_nocancel () from /lib/libc.so.6
        fstab_state = {fs_fp = 0x0, fs_buffer = 0x0, fs_mntres = {mnt_fsname = 0x0, mnt_dir = 0x0, mnt_type = 0x0, mnt_opts = 0x0, mnt_freq = 0, mnt_passno = 0}, fs_ret = {fs_spec = 0x0, fs_file = 0x0, 
            fs_vfstype = 0x0, fs_mntops = 0x0, fs_type = 0x0, fs_freq = 0, fs_passno = 0}}
        __elf_set___libc_subfreeres_element_fstab_free__ = 0x7f114d254220
#1  0x00007f114dd90674 in io_loop_handler_run (ioloop=0x17aaf60) at ioloop-epoll.c:175
        ctx = 0x17cdfc0
        events = 0x17ce800
        event = 0x17aaf60
        list = 0x21
        io = 0x1
        tv = {tv_sec = 2147483, tv_usec = 0}
        events_count = 1
        t_id = 4220376
        msecs = 2147483647
        ret = -1
        i = 0
        j = 1306179422
        call = false
#2  0x00007f114dd8f451 in io_loop_run (ioloop=0x17aaf60) at ioloop.c:350
No locals.
#3  0x00000000004067c6 in cmd_auth_input (auth_socket_path=0x411950 "/usr/local/dovecot20/var/run/dovecot/auth-client", input=0x7fff059a42c0) at doveadm-auth.c:136
        client = 0x17d0fc0
#4  0x0000000000406a79 in auth_cmd_common (cmd=0x61a920, argc=2, argv=0x175c048) at doveadm-auth.c:191
        auth_socket_path = 0x0
        input = {username = 0x175c07b "xxxx", password = 0x179d088 "sdfghjk", info = {service = 0x4119da "doveadm", local_ip = {family = 0, u = {ip6 = {__in6_u = {__u6_addr8 = '\000' <repeats 15 times>, 
                    __u6_addr16 = {0, 0, 0, 0, 0, 0, 0, 0}, __u6_addr32 = {0, 0, 0, 0}}}, ip4 = {s_addr = 0}}}, remote_ip = {family = 0, u = {ip6 = {__in6_u = {__u6_addr8 = '\000' <repeats 15 times>, 
                    __u6_addr16 = {0, 0, 0, 0, 0, 0, 0, 0}, __u6_addr32 = {0, 0, 0, 0}}}, ip4 = {s_addr = 0}}}, local_port = 0, remote_port = 0}}
        c = -1
#5  0x0000000000406b1a in cmd_auth (argc=2, argv=0x175c048) at doveadm-auth.c:209
No locals.
#6  0x000000000040602f in doveadm_try_run (cmd_name=0x175c076 "auth", argc=2, argv=0x175c048) at doveadm.c:83
        cmd__foreach_end = 0x17c8650
        cmd = 0x17c8570
#7  0x00000000004062da in main (argc=2, argv=0x175c048) at doveadm.c:169
        set_roots = {0x413860, 0x0}
        service_flags = 10
        cmd_name = 0x175c076 "auth"
        error = 0x411685 "H\205\355t\034\061\333\017\037@"
        c = -1
(gdb)