Move lock guard before AddTargetInternal instead of holding the mutex for the entire target creation and causing a deadlock with the module callback when running in parallel.

Author: Jlalond

lldb/source/Target/TargetList.cpp

@@ -48,11 +48,16 @@ Status TargetList::CreateTarget(Debugger &debugger,
                                 LoadDependentFiles load_dependent_files,
                                 const OptionGroupPlatform *platform_options,
                                 TargetSP &target_sp) {
-  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
+  // Create Target Internal does not modify any state
+  // directly and instead calls into methods which
+  // themselves are thread-safe. We need to do this so
+  // the locate module call back doesn't cause a re-entry
+  // dead lock when creating the target.
   auto result = TargetList::CreateTargetInternal(
       debugger, user_exe_path, triple_str, load_dependent_files,
       platform_options, target_sp);
 
+  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
   if (target_sp && result.Success())
     AddTargetInternal(target_sp, /*do_select*/ true);
   return result;
@@ -63,11 +68,16 @@ Status TargetList::CreateTarget(Debugger &debugger,
                                 const ArchSpec &specified_arch,
                                 LoadDependentFiles load_dependent_files,
                                 PlatformSP &platform_sp, TargetSP &target_sp) {
-  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
+  // Create Target Internal does not modify any state
+  // directly and instead calls into methods which
+  // themselves are thread-safe. We need to do this so
+  // the locate module call back doesn't cause a re-entry
+  // dead lock when creating the target.
   auto result = TargetList::CreateTargetInternal(
       debugger, user_exe_path, specified_arch, load_dependent_files,
       platform_sp, target_sp);
 
+  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
   if (target_sp && result.Success())
     AddTargetInternal(target_sp, /*do_select*/ true);
   return result;