On Mon, 11 Apr 2022 at 09:58:54 +0200, Lennart Poettering wrote:
> dbus-daemon for example uses:
>
> ExecReload=/usr/bin/busctl call org.freedesktop.DBus
> /org/freedesktop/DBus org.freedesktop.DBus ReloadConfig
>
> Which is a synchronous call to reload the config: the daemon is told
> to reload it, and "busctl call" then waits for the reply before
> returning to systemd.
... and, crucially, the implementation of ReloadConfig in dbus-daemon
also waits for its own reload to have actually been done (not just put
in a queue, but actually done) *before* sending back its reply to the
caller (in this case busctl).
If you need to wait for something to have happened, then the whole chain
of interactions needs to be synchronous: all it takes to break the chain
is one component thinking "OK, I'll do that later".
smcv
