Added the top level lock to prevent clearDies from causing problems

Author: Kevin Frei

llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h

@@ -258,6 +258,7 @@ class DWARFUnit {
 
   std::shared_ptr<DWARFUnit> DWO;
 
+  mutable llvm::sys::RWMutex CUDieFreeMutex;
   mutable llvm::sys::RWMutex CUDieArrayMutex;
   mutable llvm::sys::RWMutex AllDieArrayMutex;
 

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -496,6 +496,7 @@ void DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
 }
 
 Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
+  llvm::sys::ScopedReader FreeLock(CUDieFreeMutex);
   {
     llvm::sys::ScopedReader Lock(CUDieArrayMutex);
     if ((CUDieOnly && !DieArray.empty()) || DieArray.size() > 1)
@@ -673,6 +674,7 @@ void DWARFUnit::clearDIEs(bool KeepCUDie) {
   // It depends on the implementation whether the request is fulfilled.
   // Create a new vector with a small capacity and assign it to the DieArray to
   // have previous contents freed.
+  llvm::sys::ScopedWriter FreeLock(CUDieFreeMutex);
   llvm::sys::ScopedWriter CULock(CUDieArrayMutex);
   llvm::sys::ScopedWriter AllLock(AllDieArrayMutex);
   DieArray = (KeepCUDie && !DieArray.empty())