(gdb) backtrace 
#0  0x00007fc8901e409b in raise () from /lib/libpthread.so.0
#1  0x0000000000408963 in crash (sig=11) at src/main.c:118
#2  <signal handler called>
#3  0x00000000004920cb in automount_check_gc (u=0x1e6b040) at src/automount.c:741
#4  0x0000000000482e69 in unit_check_gc (u=0x1e6b040) at src/unit.c:249
#5  0x0000000000483226 in unit_add_to_gc_queue (u=0x1e6b040) at src/unit.c:282
#6  0x0000000000483604 in bidi_set_free (u=0x1de6d30, s=0x1de8430) at src/unit.c:326
#7  0x000000000048379c in unit_free (u=0x1de6d30) at src/unit.c:352
#8  0x000000000040d027 in manager_clear_jobs_and_units (m=0x1dd41e0) at src/manager.c:408
#9  0x000000000040d406 in manager_free (m=0x1dd41e0) at src/manager.c:429
#10 0x000000000040b716 in main (argc=1, argv=0x7fff4f10db78) at src/main.c:1216



(gdb) backtrace full
#0  0x00007fc8901e409b in raise () from /lib/libpthread.so.0
No symbol table info available.
#1  0x0000000000408963 in crash (sig=11) at src/main.c:118
        rl = {rlim_cur = 18446744073709551615, rlim_max = 18446744073709551615}
        sa = {__sigaction_handler = {sa_handler = 0, sa_sigaction = 0}, sa_mask = {__val = {0 <repeats 16 times>}}, sa_flags = 0, 
          sa_restorer = 0}
        pid = 0
        __func__ = "crash"
        __PRETTY_FUNCTION__ = "crash"
#2  <signal handler called>
No symbol table info available.
#3  0x00000000004920cb in automount_check_gc (u=0x1e6b040) at src/automount.c:741
        a = 0x1e6b040
        __PRETTY_FUNCTION__ = "automount_check_gc"
#4  0x0000000000482e69 in unit_check_gc (u=0x1e6b040) at src/unit.c:249
        __PRETTY_FUNCTION__ = "unit_check_gc"
#5  0x0000000000483226 in unit_add_to_gc_queue (u=0x1e6b040) at src/unit.c:282
        __PRETTY_FUNCTION__ = "unit_add_to_gc_queue"
#6  0x0000000000483604 in bidi_set_free (u=0x1de6d30, s=0x1de8430) at src/unit.c:326
        d = _UNIT_DEPENDENCY_MAX
        i = 0xffffffffffffffff
        other = 0x1e6b040
        __PRETTY_FUNCTION__ = "bidi_set_free"
#7  0x000000000048379c in unit_free (u=0x1de6d30) at src/unit.c:352
        d = UNIT_CONFLICTED_BY
        i = 0xffffffffffffffff
        t = 0x0
        __PRETTY_FUNCTION__ = "unit_free"
#8  0x000000000040d027 in manager_clear_jobs_and_units (m=0x1dd41e0) at src/manager.c:408
        j = 0x0
        u = 0x1de6d30
        __PRETTY_FUNCTION__ = "manager_clear_jobs_and_units"
#9  0x000000000040d406 in manager_free (m=0x1dd41e0) at src/manager.c:429
        c = UNIT_SERVICE
        __PRETTY_FUNCTION__ = "manager_free"
#10 0x000000000040b716 in main (argc=1, argv=0x7fff4f10db78) at src/main.c:1216
        m = 0x1dd41e0
        r = 5
        retval = 1
        fds = 0x0
        reexecute = false
        shutdown_verb = 0x496671 "poweroff"
        initrd_timestamp = {realtime = 0, monotonic = 0}
        systemd = "systemd"
        __func__ = "main"
        __PRETTY_FUNCTION__ = "main"