Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
@@ -75,6 +75,10 @@
   std::unique_ptr<DWARFDebugAranges>
       m_cu_aranges_ap; // A quick address to compile unit table
 
+  // Protect m_compile_units.
+  // C++14: mutable std::shared_timed_mutex m_dwz_uniq_mutex;
+  mutable std::recursive_mutex m_dwz_uniq_mutex;
+
 private:
   // All parsing needs to be done partially any managed by this class as
   // accessors are called.
Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -39,6 +39,8 @@
 // SetDwarfData
 //----------------------------------------------------------------------
 void DWARFDebugInfo::SetDwarfData(SymbolFileDWARF *dwarf2Data) {
+  // C++14: std::lock_guard<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   m_dwarf2Data = dwarf2Data;
   m_compile_units.clear();
 }
@@ -94,36 +96,51 @@
 }
 
 void DWARFDebugInfo::ParseCompileUnitHeadersIfNeeded() {
-  if (m_compile_units.empty()) {
-    if (m_dwarf2Data != NULL) {
-      lldb::offset_t file_offset = 0;
-      for (;;) {
-        DWARFCompileUnitSP cu_sp =
-            DWARFCompileUnit::Extract(m_dwarf2Data, &file_offset);
-        if (cu_sp.get() == NULL)
-          break;
-
-        m_compile_units.push_back(cu_sp);
-
-        file_offset = cu_sp->GetNextCompileUnitFileOffset();
-      }
+  {
+    // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+    std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
+    if (!m_compile_units.empty())
+      return;
+  }
+  if (m_dwarf2Data == NULL)
+    return;
+  lldb::offset_t file_offset = 0;
+  for (;;) {
+    DWARFCompileUnitSP cu_sp =
+        DWARFCompileUnit::Extract(m_dwarf2Data, &file_offset);
+    if (cu_sp.get() == NULL)
+      break;
+
+    {
+      // C++14: std::lock_guard<std::shared_timed_mutex>
+      // guard(m_dwz_uniq_mutex);
+      std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
+      m_compile_units.push_back(cu_sp);
     }
+
+    file_offset = cu_sp->GetNextCompileUnitFileOffset();
   }
 }
 
 size_t DWARFDebugInfo::GetNumCompileUnits() {
   ParseCompileUnitHeadersIfNeeded();
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   return m_compile_units.size();
 }
 
 DWARFCompileUnit *DWARFDebugInfo::GetCompileUnitAtIndex(uint32_t idx) {
   DWARFCompileUnit *cu = NULL;
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   if (idx < GetNumCompileUnits())
     cu = m_compile_units[idx].get();
   return cu;
 }
 
 bool DWARFDebugInfo::ContainsCompileUnit(const DWARFCompileUnit *cu) const {
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   // Not a verify efficient function, but it is handy for use in assertions
   // to make sure that a compile unit comes from a debug information file.
   CompileUnitColl::const_iterator end_pos = m_compile_units.end();
@@ -143,6 +160,8 @@
 
 DWARFCompileUnit *DWARFDebugInfo::GetCompileUnit(dw_offset_t cu_offset,
                                                  uint32_t *idx_ptr) {
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   DWARFCompileUnitSP cu_sp;
   uint32_t cu_idx = DW_INVALID_INDEX;
   if (cu_offset != DW_INVALID_OFFSET) {
@@ -185,6 +204,8 @@
 DWARFDebugInfo::GetCompileUnitContainingDIEOffset(dw_offset_t die_offset) {
   ParseCompileUnitHeadersIfNeeded();
 
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   DWARFCompileUnitSP cu_sp;
 
   // Watch out for single compile unit executable as they are pretty common
@@ -494,6 +515,8 @@
   CompileUnitColl::const_iterator pos;
   uint32_t curr_depth = 0;
   ParseCompileUnitHeadersIfNeeded();
+  // C++14: std::shared_lock<std::shared_timed_mutex> guard(m_dwz_uniq_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_dwz_uniq_mutex);
   for (pos = m_compile_units.begin(); pos != m_compile_units.end(); ++pos) {
     DWARFCompileUnit *cu = pos->get();
     DumpCallback(m_dwarf2Data, cu, NULL, 0, curr_depth, &dumpInfo);