From 36137497f1e2b3324ca84550f4f295dcd605d1fa Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Mon, 4 Dec 2017 18:57:55 -0500
Subject: Block ActivateBestChain to empty validationinterface queue

---
 src/validation.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'src/validation.cpp')

diff --git a/src/validation.cpp b/src/validation.cpp
index 71a51c499..23ce6509d 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -40,6 +40,7 @@
 #include <validationinterface.h>
 #include <warnings.h>
 
+#include <future>
 #include <sstream>
 
 #include <boost/algorithm/string/replace.hpp>
@@ -2566,6 +2567,18 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
     int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
     do {
         boost::this_thread::interruption_point();
+
+        if (GetMainSignals().CallbacksPending() > 10) {
+            // Block until the validation queue drains. This should largely
+            // never happen in normal operation, however may happen during
+            // reindex, causing memory blowup  if we run too far ahead.
+            std::promise<void> promise;
+            CallFunctionInValidationInterfaceQueue([&promise] {
+                promise.set_value();
+            });
+            promise.get_future().wait();
+        }
+
         if (ShutdownRequested())
             break;
 
-- 
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