Apply suggestions from code review

Co-authored-by: Jonas Devlieghere <[email protected]>

Author: kusmour

lldb/tools/lldb-dap/DAP.h

@@ -207,7 +207,7 @@ struct DAP {
   /// The set of features supported by the connected client.
   llvm::DenseSet<ClientFeature> clientFeatures;
 
-  /// The initial thread list upon attaching
+  /// The initial thread list upon attaching.
   std::optional<llvm::json::Array> initial_thread_list;
 
   /// Creates a new DAP sessions.

lldb/tools/lldb-dap/Handler/ThreadsRequestHandler.cpp

@@ -63,8 +63,9 @@ void ThreadsRequestHandler::operator()(
   if (dap.initial_thread_list) {
     threads = dap.initial_thread_list.value();
     dap.initial_thread_list.reset();
-  } else
+  } else {
     threads = GetThreads(dap.target.GetProcess(), dap.thread_format);
+  }
 
   if (threads.size() == 0) {
     response["success"] = llvm::json::Value(false);

lldb/tools/lldb-dap/JSONUtils.cpp

@@ -871,6 +871,9 @@ llvm::json::Value CreateThread(lldb::SBThread &thread, lldb::SBFormat &format) {
 }
 
 llvm::json::Array GetThreads(lldb::SBProcess process, lldb::SBFormat &format) {
+  lldb::SBMutex lock = process.GetTarget().GetAPIMutex();
+  std::lock_guard<lldb::SBMutex> guard(lock);
+  
   llvm::json::Array threads;
   const uint32_t num_threads = process.GetNumThreads();
   for (uint32_t thread_idx = 0; thread_idx < num_threads; ++thread_idx) {