refactor: Replace g_genesis_wait_cv with m_tip_block_cv

They achieve the same, but the extra indirection over boost::signals2 is
not needed.

Author: MarcoFalke

src/init.cpp

@@ -685,21 +685,6 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     argsman.AddHiddenArgs(hidden_args);
 }
 
-static bool fHaveGenesis = false;
-static GlobalMutex g_genesis_wait_mutex;
-static std::condition_variable g_genesis_wait_cv;
-
-static void BlockNotifyGenesisWait(const CBlockIndex* pBlockIndex)
-{
-    if (pBlockIndex != nullptr) {
-        {
-            LOCK(g_genesis_wait_mutex);
-            fHaveGenesis = true;
-        }
-        g_genesis_wait_cv.notify_all();
-    }
-}
-
 #if HAVE_SYSTEM
 static void StartupNotify(const ArgsManager& args)
 {
@@ -1616,7 +1601,8 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     // ********************************************************* Step 7: load block chain
 
     node.notifications = std::make_unique<KernelNotifications>(Assert(node.shutdown_request), node.exit_status, *Assert(node.warnings));
-    ReadNotificationArgs(args, *node.notifications);
+    auto& kernel_notifications{*node.notifications};
+    ReadNotificationArgs(args, kernel_notifications);
 
     // cache size calculations
     CacheSizes cache_sizes = CalculateCacheSizes(args, g_enabled_filter_types.size());
@@ -1768,15 +1754,6 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         }
     }
 
-    // Either install a handler to notify us when genesis activates, or set fHaveGenesis directly.
-    // No locking, as this happens before any background thread is started.
-    boost::signals2::connection block_notify_genesis_wait_connection;
-    if (WITH_LOCK(chainman.GetMutex(), return chainman.ActiveChain().Tip() == nullptr)) {
-        block_notify_genesis_wait_connection = uiInterface.NotifyBlockTip_connect(std::bind(BlockNotifyGenesisWait, std::placeholders::_2));
-    } else {
-        fHaveGenesis = true;
-    }
-
 #if HAVE_SYSTEM
     const std::string block_notify = args.GetArg("-blocknotify", "");
     if (!block_notify.empty()) {
@@ -1821,15 +1798,11 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     });
 
     // Wait for genesis block to be processed
-    {
-        WAIT_LOCK(g_genesis_wait_mutex, lock);
-        // We previously could hang here if shutdown was requested prior to
-        // ImportBlocks getting started, so instead we just wait on a timer to
-        // check ShutdownRequested() regularly.
-        while (!fHaveGenesis && !ShutdownRequested(node)) {
-            g_genesis_wait_cv.wait_for(lock, std::chrono::milliseconds(500));
-        }
-        block_notify_genesis_wait_connection.disconnect();
+    if (WITH_LOCK(chainman.GetMutex(), return chainman.ActiveTip() == nullptr)) {
+        WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);
+        kernel_notifications.m_tip_block_cv.wait(lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {
+            return !kernel_notifications.m_tip_block.IsNull() || ShutdownRequested(node);
+        });
     }
 
     if (ShutdownRequested(node)) {