Merge commit 'd6ebd84862f5' from swift/release/5.3 into swift/master

Author: git apple-llvm automerger

lldb/include/lldb/Symbol/Function.h

@@ -17,6 +17,8 @@
 #include "lldb/Utility/UserID.h"
 #include "llvm/ADT/ArrayRef.h"
 
+#include <mutex>
+
 namespace lldb_private {
 
 class ExecutionContext;
@@ -644,6 +646,9 @@ class Function : public UserID, public SymbolContextScope {
   uint32_t
       m_prologue_byte_size; ///< Compute the prologue size once and cache it
 
+  std::mutex
+      m_call_edges_lock; ///< Exclusive lock that controls read/write
+                         ///  access to m_call_edges and m_call_edges_resolved.
   bool m_call_edges_resolved = false; ///< Whether call site info has been
                                       ///  parsed.
   std::vector<std::unique_ptr<CallEdge>> m_call_edges; ///< Outgoing call edges.

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -4118,6 +4118,11 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
 
 std::vector<std::unique_ptr<lldb_private::CallEdge>>
 SymbolFileDWARF::ParseCallEdgesInFunction(UserID func_id) {
+  // ParseCallEdgesInFunction must be called at the behest of an exclusively
+  // locked lldb::Function instance. Storage for parsed call edges is owned by
+  // the lldb::Function instance: locking at the SymbolFile level would be too
+  // late, because the act of storing results from ParseCallEdgesInFunction
+  // would be racy.
   DWARFDIE func_die = GetDIE(func_id.GetID());
   if (func_die.IsValid())
     return CollectCallEdges(GetObjectFile()->GetModule(), func_die);

lldb/source/Symbol/Function.cpp

@@ -310,6 +310,8 @@ void Function::GetEndLineSourceInfo(FileSpec &source_file, uint32_t &line_no) {
 }
 
 llvm::ArrayRef<std::unique_ptr<CallEdge>> Function::GetCallEdges() {
+  std::lock_guard<std::mutex> guard(m_call_edges_lock);
+
   if (m_call_edges_resolved)
     return m_call_edges;