GeezerVison

This extension module has some module state values which may be read or written in different threads:

• field_limit: A simple integer value to store the maximum field size for the parser;
• dialects: A dict value to store all the dialects by string names.

field_limit

There is a public function field_size_limit that can read and write it, using a critical section to protect it. For other internal usages, _Py_atomic_load_long and _Py_atomic_store_long are used to make it thread safe.

dialects

There are three public functions get_dialect, unregister_dialect and list_dialects that can access this field. For the first two functions, a critical section is used to protect it.

And the list_dialects function just returns the dict's keys with PyDict_Keys. I think its result is readonly and PyDict_Keys itself is thread safe, so we don't need to do anything.
Other internal usages of dialects involve accessing its value with get_dialect_from_registry, which simply calls PyDict_GetItemRef and returns the result. I think we don't need to change it too.

Update: I think these APIs is just call dict APIs which is already thread-safe, and there are no other state changes inside these APIs, and no intermediate variables need to protect in these functions, so we don't need add locks on them.

• Issue: Audit all built-in modules for thread safety #116738