Added exception translator specific mutex used with try_translate_exceptions

Fixes pybind#5346

Author: vfdev-5

include/pybind11/detail/exception_translation.h

@@ -50,7 +50,7 @@ inline void try_translate_exceptions() {
         - delegate translation to the next translator by throwing a new type of exception.
         */
 
-    bool handled = with_internals([&](internals &internals) {
+    bool handled = with_internals_for_exception_translator([&](internals &internals) {
         auto &local_exception_translators = get_local_internals().registered_exception_translators;
         if (detail::apply_exception_translators(local_exception_translators)) {
             return true;

include/pybind11/detail/internals.h

@@ -177,6 +177,7 @@ static_assert(sizeof(instance_map_shard) % 64 == 0,
 struct internals {
 #ifdef Py_GIL_DISABLED
     pymutex mutex;
+    pymutex exception_translator_mutex;
 #endif
     // std::type_index -> pybind11's type information
     type_map<type_info *> registered_types_cpp;
@@ -641,6 +642,15 @@ inline auto with_internals(const F &cb) -> decltype(cb(get_internals())) {
     return cb(internals);
 }
 
+template <typename F>
+inline auto with_internals_for_exception_translator(const F &cb) -> decltype(cb(get_internals())) {
+    auto &internals = get_internals();
+#ifdef Py_GIL_DISABLED
+    std::unique_lock<pymutex> lock((internals).exception_translator_mutex);
+#endif
+    return cb(internals);
+}
+
 inline std::uint64_t mix64(std::uint64_t z) {
     // David Stafford's variant 13 of the MurmurHash3 finalizer popularized
     // by the SplitMix PRNG.

include/pybind11/pybind11.h

@@ -2573,7 +2573,7 @@ void implicitly_convertible() {
 }
 
 inline void register_exception_translator(ExceptionTranslator &&translator) {
-    detail::with_internals([&](detail::internals &internals) {
+    detail::with_internals_for_exception_translator([&](detail::internals &internals) {
         internals.registered_exception_translators.push_front(
             std::forward<ExceptionTranslator>(translator));
     });
@@ -2586,7 +2586,7 @@ inline void register_exception_translator(ExceptionTranslator &&translator) {
  * the exception.
  */
 inline void register_local_exception_translator(ExceptionTranslator &&translator) {
-    detail::with_internals([&](detail::internals &internals) {
+    detail::with_internals_for_exception_translator([&](detail::internals &internals) {
         (void) internals;
         detail::get_local_internals().registered_exception_translators.push_front(
             std::forward<ExceptionTranslator>(translator));