From 3c665065f132fd80ea3b1733785b98e45c8b371e Mon Sep 17 00:00:00 2001
From: TheCharlatan <seb.kung@gmail.com>
Date: Thu, 22 Aug 2024 22:22:01 +0200
Subject: [PATCH] node: Track last block that received a blockTip notification

---
 src/node/interfaces.cpp           | 10 ++++++----
 src/node/kernel_notifications.cpp |  6 ++++++
 src/node/kernel_notifications.h   | 12 +++++++++++-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/node/interfaces.cpp b/src/node/interfaces.cpp
index 5087c300ed992..1a0d1fdde435e 100644
--- a/src/node/interfaces.cpp
+++ b/src/node/interfaces.cpp
@@ -34,6 +34,7 @@
 #include <node/interface_ui.h>
 #include <node/mini_miner.h>
 #include <node/miner.h>
+#include <node/kernel_notifications.h>
 #include <node/transaction.h>
 #include <node/types.h>
 #include <node/warnings.h>
@@ -879,14 +880,14 @@ class MinerImpl : public Mining
         // std::chrono does not check against overflow
         if (deadline < now) deadline = std::chrono::steady_clock::time_point::max();
         {
-            WAIT_LOCK(g_best_block_mutex, lock);
-            while ((g_best_block == uint256() || g_best_block == current_tip) && !chainman().m_interrupt) {
+            WAIT_LOCK(notifications().m_tip_block_mutex, lock);
+            while ((notifications().m_tip_block == uint256() || notifications().m_tip_block == current_tip) && !chainman().m_interrupt) {
                 now = std::chrono::steady_clock::now();
                 if (now >= deadline) break;
-                g_best_block_cv.wait_until(lock, std::min(deadline, now + tick));
+                notifications().m_tip_block_cv.wait_until(lock, std::min(deadline, now + tick));
             }
         }
-        // Must release g_best_block_mutex before locking cs_main, to avoid deadlocks.
+        // Must release m_tip_block_mutex before locking cs_main, to avoid deadlocks.
         LOCK(::cs_main);
         return BlockRef{chainman().ActiveChain().Tip()->GetBlockHash(), chainman().ActiveChain().Tip()->nHeight};
     }
@@ -923,6 +924,7 @@ class MinerImpl : public Mining
 
     NodeContext* context() override { return &m_node; }
     ChainstateManager& chainman() { return *Assert(m_node.chainman); }
+    KernelNotifications& notifications() { return *Assert(m_node.notifications); }
     NodeContext& m_node;
 };
 } // namespace
diff --git a/src/node/kernel_notifications.cpp b/src/node/kernel_notifications.cpp
index 9894052a3a0ef..9b41c00404c10 100644
--- a/src/node/kernel_notifications.cpp
+++ b/src/node/kernel_notifications.cpp
@@ -50,6 +50,12 @@ namespace node {
 
 kernel::InterruptResult KernelNotifications::blockTip(SynchronizationState state, CBlockIndex& index)
 {
+    {
+        LOCK(m_tip_block_mutex);
+        m_tip_block= index.GetBlockHash();
+        m_tip_block_cv.notify_all();
+    }
+
     uiInterface.NotifyBlockTip(state, &index);
     if (m_stop_at_height && index.nHeight >= m_stop_at_height) {
         if (!m_shutdown()) {
diff --git a/src/node/kernel_notifications.h b/src/node/kernel_notifications.h
index e37f4d4e1e4bc..9ff980ea56dfd 100644
--- a/src/node/kernel_notifications.h
+++ b/src/node/kernel_notifications.h
@@ -7,6 +7,10 @@
 
 #include <kernel/notifications_interface.h>
 
+#include <sync.h>
+#include <threadsafety.h>
+#include <uint256.h>
+
 #include <atomic>
 #include <cstdint>
 
@@ -34,7 +38,7 @@ class KernelNotifications : public kernel::Notifications
     KernelNotifications(util::SignalInterrupt& shutdown, std::atomic<int>& exit_status, node::Warnings& warnings)
         : m_shutdown(shutdown), m_exit_status{exit_status}, m_warnings{warnings} {}
 
-    [[nodiscard]] kernel::InterruptResult blockTip(SynchronizationState state, CBlockIndex& index) override;
+    [[nodiscard]] kernel::InterruptResult blockTip(SynchronizationState state, CBlockIndex& index) override EXCLUSIVE_LOCKS_REQUIRED(!m_tip_block_mutex);
 
     void headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync) override;
 
@@ -52,6 +56,12 @@ class KernelNotifications : public kernel::Notifications
     int m_stop_at_height{DEFAULT_STOPATHEIGHT};
     //! Useful for tests, can be set to false to avoid shutdown on fatal error.
     bool m_shutdown_on_fatal_error{true};
+
+    Mutex m_tip_block_mutex;
+    std::condition_variable m_tip_block_cv;
+    //! The block for which the last blockTip notification was received for.
+    uint256 m_tip_block;
+
 private:
     util::SignalInterrupt& m_shutdown;
     std::atomic<int>& m_exit_status;