node: Track last block that received a blockTip notification

Also signal m_tip_block_cv when StopRPC is called, for
consistency with g_best_block_cv. This is handled in
StopRPC instead of OnRPCStopped() because the latter
is deleted in a later commit.

Co-authored-by: TheCharlatan <seb.kung@gmail.com>
Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/rpc/server.cpp

@@ -11,6 +11,7 @@
 #include <common/system.h>
 #include <logging.h>
 #include <node/context.h>
+#include <node/kernel_notifications.h>
 #include <rpc/server_util.h>
 #include <rpc/util.h>
 #include <sync.h>
@@ -311,16 +312,19 @@ void InterruptRPC()
     });
 }
 
-void StopRPC()
+void StopRPC(const std::any& context)
 {
     static std::once_flag g_rpc_stop_flag;
     // This function could be called twice if the GUI has been started with -server=1.
     assert(!g_rpc_running);
-    std::call_once(g_rpc_stop_flag, []() {
+    std::call_once(g_rpc_stop_flag, [&]() {
         LogDebug(BCLog::RPC, "Stopping RPC\n");
         WITH_LOCK(g_deadline_timers_mutex, deadlineTimers.clear());
         DeleteAuthCookie();
         g_rpcSignals.Stopped();
+        node::NodeContext& node = EnsureAnyNodeContext(context);
+        // The notifications interface doesn't exist between initialization step 4a and 7.
+        if (node.notifications) node.notifications->m_tip_block_cv.notify_all();
     });
 }