rpc: move state stop into virNetDaemon class

Currently the remote daemon code is responsible for calling virStateStop
in a background thread. The virNetDaemon code wants to synchronize with
this during shutdown, however, so the virThreadPtr must be passed over.

Even the limited synchronization done currently, however, is flawed and
to fix this requires the virNetDaemon code to be responsible for calling
virStateStop in a thread more directly.

Thus the logic is moved over into virStateStop via a further callback
to be registered by the remote daemon.

Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/libvirt_remote.syms

@@ -95,7 +95,7 @@ virNetDaemonQuitExecRestart;
 virNetDaemonRemoveShutdownInhibition;
 virNetDaemonRun;
 virNetDaemonSetLifecycleCallbacks;
-virNetDaemonSetStateStopWorkerThread;
+virNetDaemonStop;
 virNetDaemonUpdateServices;
 
 

src/remote/remote_daemon.c

@@ -514,41 +514,6 @@ static void daemonInhibitCallback(bool inhibit, void *opaque)
 static GDBusConnection *sessionBus;
 static GDBusConnection *systemBus;
 
-static void daemonStopWorker(void *opaque)
-{
-    virNetDaemon *dmn = opaque;
-
-    VIR_DEBUG("Begin stop dmn=%p", dmn);
-
-    ignore_value(virStateStop());
-
-    VIR_DEBUG("Completed stop dmn=%p", dmn);
-
-    /* Exit daemon cleanly */
-    virNetDaemonQuit(dmn);
-}
-
-
-/* We do this in a thread to not block the main loop */
-static void daemonStop(virNetDaemon *dmn)
-{
-    virThread *thr;
-    virObjectRef(dmn);
-
-    thr = g_new0(virThread, 1);
-
-    if (virThreadCreateFull(thr, true,
-                            daemonStopWorker,
-                            "daemon-stop", false, dmn) < 0) {
-        virObjectUnref(dmn);
-        g_free(thr);
-        return;
-    }
-
-    virNetDaemonSetStateStopWorkerThread(dmn, &thr);
-}
-
-
 static GDBusMessage *
 handleSessionMessageFunc(GDBusConnection *connection G_GNUC_UNUSED,
                          GDBusMessage *message,
@@ -562,7 +527,7 @@ handleSessionMessageFunc(GDBusConnection *connection G_GNUC_UNUSED,
     if (virGDBusMessageIsSignal(message,
                                 "org.freedesktop.DBus.Local",
                                 "Disconnected"))
-        daemonStop(dmn);
+        virNetDaemonStop(dmn);
 
     return message;
 }
@@ -581,7 +546,7 @@ handleSystemMessageFunc(GDBusConnection *connection G_GNUC_UNUSED,
 
     VIR_DEBUG("dmn=%p", dmn);
 
-    daemonStop(dmn);
+    virNetDaemonStop(dmn);
 }
 
 
@@ -625,6 +590,7 @@ static void daemonRunStateInit(void *opaque)
     g_atomic_int_set(&driversInitialized, 1);
 
     virNetDaemonSetLifecycleCallbacks(dmn,
+                                      virStateStop,
                                       virStateShutdownPrepare,
                                       virStateShutdownWait);
 

src/rpc/virnetdaemon.c

@@ -65,6 +65,7 @@ struct _virNetDaemon {
     GHashTable *servers;
     virJSONValue *srvObject;
 
+    virNetDaemonLifecycleCallback stopCb;
     virNetDaemonLifecycleCallback shutdownPrepareCb;
     virNetDaemonLifecycleCallback shutdownWaitCb;
     virThread *stateStopThread;
@@ -793,8 +794,10 @@ virNetDaemonRun(virNetDaemon *dmn)
         }
     }
 
+    VIR_DEBUG("Main loop exited");
     if (dmn->graceful) {
         virThreadJoin(&shutdownThread);
+        VIR_DEBUG("Graceful shutdown complete");
     } else {
         VIR_WARN("Make forcefull daemon shutdown");
         exit(EXIT_FAILURE);
@@ -805,17 +808,6 @@ virNetDaemonRun(virNetDaemon *dmn)
 }
 
 
-void
-virNetDaemonSetStateStopWorkerThread(virNetDaemon *dmn,
-                                     virThread **thr)
-{
-    VIR_LOCK_GUARD lock = virObjectLockGuard(dmn);
-
-    VIR_DEBUG("Setting state stop worker thread on dmn=%p to thr=%p", dmn, thr);
-    dmn->stateStopThread = g_steal_pointer(thr);
-}
-
-
 void
 virNetDaemonQuit(virNetDaemon *dmn)
 {
@@ -837,6 +829,44 @@ virNetDaemonQuitExecRestart(virNetDaemon *dmn)
 }
 
 
+static void
+virNetDaemonStopWorker(void *opaque)
+{
+    virNetDaemon *dmn = opaque;
+
+    VIR_DEBUG("Begin stop dmn=%p", dmn);
+
+    dmn->stopCb();
+
+    VIR_DEBUG("Completed stop dmn=%p", dmn);
+
+    virNetDaemonQuit(dmn);
+    virObjectUnref(dmn);
+}
+
+
+void
+virNetDaemonStop(virNetDaemon *dmn)
+{
+    VIR_LOCK_GUARD lock = virObjectLockGuard(dmn);
+
+    if (!dmn->stopCb ||
+        dmn->stateStopThread)
+        return;
+
+    virObjectRef(dmn);
+    dmn->stateStopThread = g_new0(virThread, 1);
+
+    if (virThreadCreateFull(dmn->stateStopThread, true,
+                            virNetDaemonStopWorker,
+                            "daemon-stop", false, dmn) < 0) {
+        virObjectUnref(dmn);
+        g_clear_pointer(&dmn->stateStopThread, g_free);
+        return;
+    }
+}
+
+
 static int
 daemonServerClose(void *payload,
                   const char *key G_GNUC_UNUSED,
@@ -874,11 +904,20 @@ virNetDaemonHasClients(virNetDaemon *dmn)
 
 void
 virNetDaemonSetLifecycleCallbacks(virNetDaemon *dmn,
+                                  virNetDaemonLifecycleCallback stopCb,
                                   virNetDaemonLifecycleCallback prepareCb,
                                   virNetDaemonLifecycleCallback waitCb)
 {
     VIR_LOCK_GUARD lock = virObjectLockGuard(dmn);
 
+    VIR_DEBUG("Lifecycle callbacks stop=%p prepare=%p wait=%p",
+              stopCb, prepareCb, waitCb);
+
+    /* Immutable once set */
+    if (dmn->stopCb || dmn->shutdownPrepareCb || dmn->shutdownWaitCb)
+        return;
+
+    dmn->stopCb = stopCb;
     dmn->shutdownPrepareCb = prepareCb;
     dmn->shutdownWaitCb = waitCb;
 }

src/rpc/virnetdaemon.h

@@ -66,13 +66,11 @@ int virNetDaemonAddSignalHandler(virNetDaemon *dmn,
 void virNetDaemonUpdateServices(virNetDaemon *dmn,
                                 bool enabled);
 
-void virNetDaemonSetStateStopWorkerThread(virNetDaemon *dmn,
-                                          virThread **thr);
-
 void virNetDaemonRun(virNetDaemon *dmn);
 
 void virNetDaemonQuit(virNetDaemon *dmn);
 void virNetDaemonQuitExecRestart(virNetDaemon *dmn);
+void virNetDaemonStop(virNetDaemon *dmn);
 
 bool virNetDaemonHasClients(virNetDaemon *dmn);
 
@@ -84,6 +82,29 @@ bool virNetDaemonHasServer(virNetDaemon *dmn,
 
 typedef int (*virNetDaemonLifecycleCallback)(void);
 
+/*
+ * @stopCb: preserves any active state on host shutdown / session exit
+ * @prepareCb: start shutting down daemon
+ * @waitCb: wait for shutdown completion
+ *
+ * This method may only be invoked once, the callbacks are immutable
+ * once set.
+ *
+ * On host shutdown (privileged) or session exit (unprivileged)
+ * the @stopCb will be invoked first.
+ *
+ * When the daemon shuts down, the sequence of operations is
+ * as follows
+ *
+ * - Listener stops accepting new clients
+ * - Existing clients are closed
+ * - Delay until @stopCb is complete (if still running)
+ * - @prepareCb invoked
+ * - Server worker pool is drained in background
+ * - @waitCb is invoked in background
+ * - Main loop terminates
+ */
 void virNetDaemonSetLifecycleCallbacks(virNetDaemon *dmn,
+                                       virNetDaemonLifecycleCallback stopCb,
                                        virNetDaemonLifecycleCallback prepareCb,
                                        virNetDaemonLifecycleCallback waitCb);