Created attachment 1408455 [details]
Reproducer

I cannot reproduce the issue if the "test" service is inactive.
The "test" service requires a stateless "test-init" service.
Having the "test-init" with RemainAfterExit=yes (stateful service) and "test-init" already started doesn't make the issue happen.

This seems the issue is due to having the "test-init" service be spawned at the time of the systemd-reload.

Using strace without "-x" (no hex dump), we can indeed see the query on test-init.service:

3683  16:12:11.210692 recvmsg(3<socket:[40648]>, {msg_name(0)=NULL, msg_iov(1)=[{"/org/freedesktop/systemd1\0\0\0\0\0\0\0\2\1s\0 \0\0\0org.freedesktop.systemd1.Manager\0\0\0\0\0\0\0\0\3\1s\0\n\0\0\0JobRemoved\0\0\0\0\0\0\10\1g\0\4uoss\0\0\0\0\0\0\0\265\f\0\0\"\0\0\0/org/freedesktop/systemd1/job/3253\0\0\21\0\0\0test-init.service\0\0\0\4\0\0\0done\0", 197}], msg_controllen=32, [{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, {pid=1, uid=0, gid=0}}], msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_CMSG_CLOEXEC) = 197 <0.000009>

Then the status (inactive/dead):

3683  16:12:11.210861 recvmsg(3<socket:[40648]>, {msg_name(0)=NULL, msg_iov(1)=[{"/org/freedesktop/systemd1/unit/test_2dinit_2eservice\0\0\0\0\2\1s\0\37\0\0\0org.freedesktop.DBus.Properties\0\3\1s\0\21\0\0\0PropertiesChanged\0\0\0\0\0\0\0\10\1g\0\10sa{sv}as\0\0\0\35\0\0\0org.freedesktop.systemd1.Unit\0\0\0\240\2\0\0\v\0\0\0ActiveState\0\1s\0\0\10\0\0\0inactive\0\0\0\0\0\0\0\0\10\0\0\0SubState\0\1s\0\4\0\0\0dead\0\0\0\0\0\0\0\0\25\0\0\0InactiveExitTimestamp\0\1t\0\0\0\0\227Oi\352tg\5\0\36\0\0\0InactiveExitTimestampMonotonic\0\1t\0\0\0\272\311\242\315\0\0\0\0\24\0\0\0ActiveEnterTimestamp\0\1t\0\0\0\0\0\313\24\272\272tg\5\0\35\0\0\0ActiveEnterTimestampMonotonic\0\1t\0\0\0\0\356\216\363\235\0\0\0\0\23\0\0\0ActiveExitTimestamp\0\1t\0\0\0\0\0\0\2021\253\347tg\5\0\34\0\0\0ActiveExitTimestampMonotonic\0\1t\0\0\0\0\0\244\253\344\312\0\0\0\0\26\0\0\0InactiveEnterTimestamp\0\1t\0\0\0\352\323x\352tg\5\0\37\0\0\0InactiveEnterTimestampMonotonic\0\1t\0\0\rN\262\315\0\0\0\0\3\0\0\0Job\0\4(uo)\0\0\0\0\0\0\0\1\0\0\0/\0\0\0\0\0\0\0\17\0\0\0ConditionResult\0\1b\0\0\1\0\0\0\0\0\0\0\f\0\0\0AssertResult\0\1b\0\1\0\0\0\22\0\0\0ConditionTimestamp\0\1t\0\0\0\0\0\0\0TLi\352tg\5\0\33\0\0\0ConditionTimestampMonotonic\0\1t\0\0\0\0\0\0w\306\242\315\0\0\0\0\17\0\0\0AssertTimestamp\0\1t\0\0TLi\352tg\5\0\30\0\0\0AssertTimestampMonotonic\0\1t\0w\306\242\315\0\0\0\0\0\0\0\0", 860}], msg_controllen=32, [{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, {pid=1, uid=0, gid=0}}], msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_CMSG_CLOEXEC) = 860 <0.000008>


And finally some recvmsg/poll forever until command is killed:

3683  16:12:11.210903 recvmsg(3<socket:[40648]>, 0x7fff169f2f10, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable) <0.000008>
3683  16:12:11.210935 ppoll([{fd=3<socket:[40648]>, events=POLLIN}], 1, NULL, NULL, 8) = ? ERESTARTNOHAND (To be restarted if no handler) <10.424494>

Created attachment 1408708 [details]
strace of working/non-working "systemctl start" command

Comparing systemctl_ok.strace and systemctl_ko.strace, we can see the following:

- sendmsg() are identical
- recvmsg() are identical, up to reading test-init.service status

recvmsg() missing from systemctl_ko.strace is the following: notification job "test.service" is done

systemd likely 'lost' that information while reloading

Also happens with other services which depend on another service and the latter has to run (e.g. sshd.service depends on sshd-keygen.service and there is no host key in /etc/ssh/).

I've got issue with same symptoms, in my case there was a problem with dbus service.
System Centos-7.5 built from scratch. dbus=1.10 systemd=219
1. dbus creates socket in /run/dbus/ but services like hostnamectl and systemd expect it in /var/run/dbus
2. Package systemd-sysv needs to be installed

(In reply to Maxim Lvov from comment #8)
> I've got issue with same symptoms, in my case there was a problem with dbus
> service.
> System Centos-7.5 built from scratch. dbus=1.10 systemd=219
> 1. dbus creates socket in /run/dbus/ but services like hostnamectl and
> systemd expect it in /var/run/dbus
> 2. Package systemd-sysv needs to be installed

Actually my issue was that during image build /var/run/ directory was created and thus system-tmpfiles doesn't create link because in /usr/lib/tmpfiles.d/var.conf it's configured to create it only if directory/link doesn't exist. For some reason it wasn't issue in 7.4

*** This bug has been marked as a duplicate of bug 1351793 ***