service: when starting a service make a copy of the watchdog timeout and use that

When we start a service process we pass the selected watchdog timeout to
it with the $WATCHDOG_USEC environment variable. If the unit file is
reconfigured later, we need to make sure to continue to honour the
original timeout, i.e. watch $WATCHDOG_USEC was set to, otherwise we'll
expect the ping at a different time as the service process is sending it
to us.

Hence, whenever we start a unit, save the watchdog timeout, and stick to
that for everything we do.

Fixes: #9467

1 files changed, 3 insertions, 2 deletions

diff --git a/src/core/service.h b/src/core/service.h
index 1206e3cdda..9c4340c70e 100644
--- a/src/core/service.h
+++ b/src/core/service.h
@@ -99,8 +99,9 @@ struct Service {
         usec_t runtime_max_usec;
 
         dual_timestamp watchdog_timestamp;
-        usec_t watchdog_usec;
-        usec_t watchdog_override_usec;
+        usec_t watchdog_usec;            /* the requested watchdog timeout in the unit file */
+        usec_t watchdog_original_usec;   /* the watchdog timeout that was in effect when the unit was started, i.e. the timeout the forked off processes currently see */
+        usec_t watchdog_override_usec;   /* the watchdog timeout requested by the service itself through sd_notify() */
         bool watchdog_override_enable;
         sd_event_source *watchdog_event_source;