nixos/switch-to-configuration: Fix restarting by activation script

This bug is so obscure and unlikely that I was honestly not able to
properly write a test for it. What happens is that we are calling
handleModifiedUnit() with $unitsToStart=\%unitsToRestart. We do this to
make sure that the unit is stopped before it's started again which is
not possible by regular means because the stop phase is already done
when calling the activation script.

recordUnit() still gets $startListFile, however which is the wrong file.
The bug would be triggered if an activation script requests a service
restart for a service that has `stopIfChanged = true` and
switch-to-configuration is killed before the restart phase was run. If
the script is run again, but the activation script is not requesting
more restarts, the unit would be started instead of restarted.

1 files changed, 10 insertions, 2 deletions

diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index ca45fc9c286..a67a9b05778 100644
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -392,7 +392,11 @@ sub handleModifiedUnit {
                             # exist in new configuration:
                             if (-e "$out/etc/systemd/system/$socket") {
                                 $unitsToStart->{$socket} = 1;
-                                recordUnit($startListFile, $socket);
+                                if ($unitsToStart eq $unitsToRestart) {
+                                    recordUnit($restartListFile, $socket);
+                                } else {
+                                    recordUnit($startListFile, $socket);
+                                }
                                 $socket_activated = 1;
                             }
                             # Remove from units to reload so we don't restart and reload
@@ -410,7 +414,11 @@ sub handleModifiedUnit {
                 # service gets restarted if we're interrupted.
                 if (!$socket_activated) {
                     $unitsToStart->{$unit} = 1;
-                    recordUnit($startListFile, $unit);
+                    if ($unitsToStart eq $unitsToRestart) {
+                        recordUnit($restartListFile, $unit);
+                    } else {
+                        recordUnit($startListFile, $unit);
+                    }
                 }
 
                 $unitsToStop->{$unit} = 1;