From 657dfc5bca2bd476d124f51f711e889f98f1e7d6 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Tue, 20 Mar 2018 21:04:27 -0700
Subject: [PATCH] Fix csBestBlock/cvBlockChange waiting in rpc/mining

Github-Pull: #12743
Rebased-From: 45dd13503918e75a45ce33eb5c934b998790fdc8
---
 src/rpc/mining.cpp | 2 +-
 src/validation.cpp | 7 ++++++-
 src/validation.h   | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index c22d0ac37..f029be7fa 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -477,7 +477,7 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
             checktxtime = std::chrono::steady_clock::now() + std::chrono::minutes(1);
 
             WaitableLock lock(csBestBlock);
-            while (chainActive.Tip()->GetBlockHash() == hashWatchedChain && IsRPCRunning())
+            while (hashBestBlock == hashWatchedChain && IsRPCRunning())
             {
                 if (cvBlockChange.wait_until(lock, checktxtime) == std::cv_status::timeout)
                 {
diff --git a/src/validation.cpp b/src/validation.cpp
index 2c5b5a1a3..7795905c4 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -210,6 +210,7 @@ CChain& chainActive = g_chainstate.chainActive;
 CBlockIndex *pindexBestHeader = nullptr;
 CWaitableCriticalSection csBestBlock;
 CConditionVariable cvBlockChange;
+uint256 hashBestBlock;
 int nScriptCheckThreads = 0;
 std::atomic_bool fImporting(false);
 std::atomic_bool fReindex(false);
@@ -2151,7 +2152,11 @@ void static UpdateTip(const CBlockIndex *pindexNew, const CChainParams& chainPar
     // New best block
     mempool.AddTransactionsUpdated(1);
 
-    cvBlockChange.notify_all();
+    {
+        WaitableLock lock(csBestBlock);
+        hashBestBlock = pindexNew->GetBlockHash();
+        cvBlockChange.notify_all();
+    }
 
     std::vector<std::string> warningMessages;
     if (!IsInitialBlockDownload())
diff --git a/src/validation.h b/src/validation.h
index cd243e204..e9a1eabdf 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -166,6 +166,7 @@ extern uint64_t nLastBlockWeight;
 extern const std::string strMessageMagic;
 extern CWaitableCriticalSection csBestBlock;
 extern CConditionVariable cvBlockChange;
+extern uint256 hashBestBlock;
 extern std::atomic_bool fImporting;
 extern std::atomic_bool fReindex;
 extern int nScriptCheckThreads;