service: Display updated WatchdogUSec from sd_notify

Suppose a service has WatchdogSec set to 2 seconds in its unit file. I
then start the service and WatchdogUSec is set correctly:

    % systemctl --user show psi-notify -p WatchdogUSec
    WatchdogUSec=2s

Now I call `sd_notify(0, "WATCHDOG_USEC=10000000")`. The new timer seems
to have taken effect, since I only send `WATCHDOG=1` every 4 seconds,
and systemd isn't triggering the watchdog handler. However, `systemctl
show` still shows WatchdogUSec as 2s:

    % systemctl --user show psi-notify -p WatchdogUSec
    WatchdogUSec=2s

This seems surprising, since this "original" watchdog timer isn't the
one taking effect any more. This patch makes it so that we instead
display the new watchdog timer after sd_notify(WATCHDOG_USEC):

    % systemctl --user show psi-notify -p WatchdogUSec
    WatchdogUSec=10s

Fixes #15726.

3 files changed, 7 insertions, 10 deletions

diff --git a/src/core/dbus-service.c b/src/core/dbus-service.c
index 984ef2459e..11680f0d69 100644
--- a/src/core/dbus-service.c
+++ b/src/core/dbus-service.c
@@ -28,6 +28,7 @@ static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_restart, service_restart, Servi
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_notify_access, notify_access, NotifyAccess);
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_emergency_action, emergency_action, EmergencyAction);
 static BUS_DEFINE_PROPERTY_GET(property_get_timeout_abort_usec, "t", Service, service_timeout_abort_usec);
+static BUS_DEFINE_PROPERTY_GET(property_get_watchdog_usec, "t", Service, service_get_watchdog_usec);
 
 static int property_get_exit_status_set(
                 sd_bus *bus,
@@ -101,7 +102,7 @@ const sd_bus_vtable bus_service_vtable[] = {
         SD_BUS_PROPERTY("TimeoutStopUSec", "t", bus_property_get_usec, offsetof(Service, timeout_stop_usec), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("TimeoutAbortUSec", "t", property_get_timeout_abort_usec, 0, 0),
         SD_BUS_PROPERTY("RuntimeMaxUSec", "t", bus_property_get_usec, offsetof(Service, runtime_max_usec), SD_BUS_VTABLE_PROPERTY_CONST),
-        SD_BUS_PROPERTY("WatchdogUSec", "t", bus_property_get_usec, offsetof(Service, watchdog_usec), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("WatchdogUSec", "t", property_get_watchdog_usec, 0, 0),
         BUS_PROPERTY_DUAL_TIMESTAMP("WatchdogTimestamp", offsetof(Service, watchdog_timestamp), 0),
         SD_BUS_PROPERTY("PermissionsStartOnly", "b", bus_property_get_bool, offsetof(Service, permissions_start_only), SD_BUS_VTABLE_PROPERTY_CONST|SD_BUS_VTABLE_HIDDEN), /* 😷 deprecated */
         SD_BUS_PROPERTY("RootDirectoryStartOnly", "b", bus_property_get_bool, offsetof(Service, root_directory_start_only), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/core/service.c b/src/core/service.c
index 6e2a82a286..a824f2d6a0 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -198,15 +198,6 @@ static void service_stop_watchdog(Service *s) {
         s->watchdog_timestamp = DUAL_TIMESTAMP_NULL;
 }
 
-static usec_t service_get_watchdog_usec(Service *s) {
-        assert(s);
-
-        if (s->watchdog_override_enable)
-                return s->watchdog_override_usec;
-
-        return s->watchdog_original_usec;
-}
-
 static void service_start_watchdog(Service *s) {
         usec_t watchdog_usec;
         int r;
diff --git a/src/core/service.h b/src/core/service.h
index b9c8036f22..3a84db14c4 100644
--- a/src/core/service.h
+++ b/src/core/service.h
@@ -200,6 +200,11 @@ static inline usec_t service_timeout_abort_usec(Service *s) {
         return s->timeout_abort_set ? s->timeout_abort_usec : s->timeout_stop_usec;
 }
 
+static inline usec_t service_get_watchdog_usec(Service *s) {
+        assert(s);
+        return s->watchdog_override_enable ? s->watchdog_override_usec : s->watchdog_original_usec;
+}
+
 extern const UnitVTable service_vtable;
 
 int service_set_socket_fd(Service *s, int fd, struct Socket *socket, bool selinux_context_net);