diff --git a/llvm/lib/ExecutionEngine/Orc/MemoryMapper.cpp b/llvm/lib/ExecutionEngine/Orc/MemoryMapper.cpp
--- a/llvm/lib/ExecutionEngine/Orc/MemoryMapper.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/MemoryMapper.cpp
@@ -412,6 +412,7 @@
 }
 
 SharedMemoryMapper::~SharedMemoryMapper() {
+  std::lock_guard<std::mutex> Lock(Mutex);
   for (const auto &R : Reservations) {
 
 #if defined(LLVM_ON_UNIX) && !defined(__ANDROID__)