[lldb] Fix unsafe map mutation in ProcessElfCore::FindModuleUUID (#159444) The `ProcessElfCore::FindModuleUUID` function can be called by multiple threads at the same time when `target.parallel-module-load` is true. We were using the `operator[]` to lookup the UUID which will mutate the map when the key is not present. This is unsafe in a multi-threaded contex so we now use a read-only `find` operation and explicitly return an invalid UUID when the key is not present. The `m_uuids` map can follow a create-then-query pattern. It is populated in the `DoLoadCore` function which looks like it is only called in a single-threaded context so we do not need extra locking as long as we keep the other accesses read-only. Other fixes I considered * Use a lock to protect access - We don't need to modify the map after creation so we can allow concurrent read-only access. * Store the map in a const pointer container to prevent accidental mutation in other places. - Only accessed in one place currently so just added a comment. * Store the UUID in the NT_FILE_Entry after building the mapping correctly in `UpdateBuildIdForNTFileEntries`. - The map lets us avoid a linear search in `FindModuleUUID`. This commit also reverts the temporary workaround from #159395 which disabled parallel module loading to avoid the test failure. Fixes #159377

diff --git a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
index 38bf135..b7029fb 100644
--- a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
+++ b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp

@@ -308,7 +308,13 @@
 }
 
 UUID ProcessElfCore::FindModuleUUID(const llvm::StringRef path) {
-  return m_uuids[std::string(path)];
+  // Lookup the UUID for the given path in the map.
+  // Note that this could be called by multiple threads so make sure
+  // we access the map in a thread safe way (i.e. don't use operator[]).
+  auto it = m_uuids.find(std::string(path));
+  if (it != m_uuids.end())
+    return it->second;
+  return UUID();
 }
 
 lldb_private::DynamicLoader *ProcessElfCore::GetDynamicLoader() {

diff --git a/lldb/test/API/functionalities/postmortem/netbsd-core/TestNetBSDCore.py b/lldb/test/API/functionalities/postmortem/netbsd-core/TestNetBSDCore.py
index 179dbdf..ff1ef21 100644
--- a/lldb/test/API/functionalities/postmortem/netbsd-core/TestNetBSDCore.py
+++ b/lldb/test/API/functionalities/postmortem/netbsd-core/TestNetBSDCore.py

@@ -117,8 +117,6 @@
                 )
 
     def do_test(self, filename, pid, region_count):
-        # Temporary workaround for https://github.com/llvm/llvm-project/issues/159377
-        self.runCmd("settings set target.parallel-module-load false")
         target = self.dbg.CreateTarget(filename)
         process = target.LoadCore(filename + ".core")