From 05d6129c4fca74b29132fb7c78fe7e4d3b4d37c1 Mon Sep 17 00:00:00 2001
From: Ben Hillis <benhillis@gmail.com>
Date: Tue, 7 Oct 2025 15:37:41 -0700
Subject: [PATCH] Implement clean instance terminate when using systemd
 (#13552)

* Implement clean instance terminate when using systemd

* pr feedback

* more pr feedback

---------

Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>
---
 src/linux/init/init.cpp                     | 65 ++++++++++++++++-----
 src/windows/service/exe/WslCoreInstance.cpp |  8 ++-
 2 files changed, 57 insertions(+), 16 deletions(-)

diff --git a/src/linux/init/init.cpp b/src/linux/init/init.cpp
index 8a48195..77495eb 100644
--- a/src/linux/init/init.cpp
+++ b/src/linux/init/init.cpp
@@ -129,6 +129,8 @@ void InitEntryUtilityVm(wsl::linux::WslDistributionConfig& Config);
 
 void InitTerminateInstance(gsl::span<gsl::byte> Buffer, wsl::shared::SocketChannel& Channel, wsl::linux::WslDistributionConfig& Config);
 
+void InitTerminateInstanceInternal(const wsl::linux::WslDistributionConfig& Config);
+
 void InstallSystemdUnit(const char* Path, const std::string& Name, const char* Content);
 
 int GenerateSystemdUnits(int Argc, char** Argv);
@@ -2507,18 +2509,7 @@ Return Value:
         }
     }
 
-    //
-    // If the distro init process was booted, use the shutdown command to terminate the instance.
-    //
-
-    if (Config.BootInit && !Config.BootStartWriteSocket)
-    {
-        UtilExecCommandLine("systemctl reboot", nullptr);
-    }
-
-    reboot(RB_POWER_OFF);
-    FATAL_ERROR("reboot(RB_POWER_OFF) failed {}", errno);
-
+    InitTerminateInstanceInternal(Config);
     return;
 }
 
@@ -2661,10 +2652,56 @@ try
     }
 
     //
-    // Respond to the instance termination request.
+    // Attempt to stop the plan9 server, if it is not able to be stopped because of an
+    // in-use file, reply to the service that the instance could not be terminated.
     //
 
-    Channel.SendResultMessage<bool>(StopPlan9Server(Message->Force, Config));
+    if (!StopPlan9Server(Message->Force, Config))
+    {
+        Channel.SendResultMessage<bool>(false);
+        return;
+    }
+
+    InitTerminateInstanceInternal(Config);
+}
+CATCH_LOG();
+
+void InitTerminateInstanceInternal(const wsl::linux::WslDistributionConfig& Config)
+
+/*++
+
+Routine Description:
+
+    This routine attempts to cleanly terminate the instance.
+
+Arguments:
+
+    Config - Supplies the distribution config.
+
+Return Value:
+
+    None.
+
+--*/
+try
+{
+    //
+    // If systemd is enabled, attempt to poweroff the instance via systemctl.
+    //
+
+    if (Config.BootInit && !Config.BootStartWriteSocket)
+    {
+        THROW_LAST_ERROR_IF(UtilSetSignalHandlers(g_SavedSignalActions, false) < 0);
+
+        if (UtilExecCommandLine("systemctl poweroff", nullptr) == 0)
+        {
+            std::this_thread::sleep_for(std::chrono::milliseconds(Config.BootInitTimeout));
+            LOG_ERROR("systemctl poweroff did not terminate the instance in {} ms, calling reboot(RB_POWER_OFF)", Config.BootInitTimeout);
+        }
+    }
+
+    reboot(RB_POWER_OFF);
+    FATAL_ERROR("reboot(RB_POWER_OFF) failed {}", errno);
 }
 CATCH_LOG();
 
diff --git a/src/windows/service/exe/WslCoreInstance.cpp b/src/windows/service/exe/WslCoreInstance.cpp
index 1765c55..7dec7f5 100644
--- a/src/windows/service/exe/WslCoreInstance.cpp
+++ b/src/windows/service/exe/WslCoreInstance.cpp
@@ -477,8 +477,12 @@ bool WslCoreInstance::RequestStop(_In_ bool Force)
             terminateMessage.Header.MessageSize = sizeof(terminateMessage);
             terminateMessage.Force = Force;
 
-            const auto& terminateResponse = m_initChannel->GetChannel().Transaction(terminateMessage, nullptr, m_socketTimeout);
-            shutdown = terminateResponse.Result;
+            m_initChannel->GetChannel().SendMessage(terminateMessage);
+            auto [message, span] = m_initChannel->GetChannel().ReceiveMessageOrClosed<RESULT_MESSAGE<bool>>(m_socketTimeout);
+            if (message)
+            {
+                shutdown = message->Result;
+            }
         }
     CATCH_LOG()