WorkerThreadPool (plus friends): Overhaul unlock allowance zones

This fixes a rare but possible deadlock, maybe due to undefined behavior. The new implementation is safer, at the cost of some added boilerplate.

(cherry picked from commit f4d76853b9d921e3645295f9bebc39eb73661e67)

1 files changed, 9 insertions, 1 deletions

diff --git a/modules/gdscript/gdscript_cache.cpp b/modules/gdscript/gdscript_cache.cpp
index 3b6526ffd9..b3c0744bdf 100644
--- a/modules/gdscript/gdscript_cache.cpp
+++ b/modules/gdscript/gdscript_cache.cpp
@@ -144,6 +144,14 @@ GDScriptParserRef::~GDScriptParserRef() {
 
 GDScriptCache *GDScriptCache::singleton = nullptr;
 
+SafeBinaryMutex<GDScriptCache::BINARY_MUTEX_TAG> &_get_gdscript_cache_mutex() {
+	return GDScriptCache::mutex;
+}
+
+template <>
+thread_local SafeBinaryMutex<GDScriptCache::BINARY_MUTEX_TAG>::TLSData SafeBinaryMutex<GDScriptCache::BINARY_MUTEX_TAG>::tls_data(_get_gdscript_cache_mutex());
+SafeBinaryMutex<GDScriptCache::BINARY_MUTEX_TAG> GDScriptCache::mutex;
+
 void GDScriptCache::move_script(const String &p_from, const String &p_to) {
 	if (singleton == nullptr || p_from == p_to) {
 		return;
@@ -369,7 +377,7 @@ Ref<GDScript> GDScriptCache::get_full_script(const String &p_path, Error &r_erro
 
 	// Allowing lifting the lock might cause a script to be reloaded multiple times,
 	// which, as a last resort deadlock prevention strategy, is a good tradeoff.
-	uint32_t allowance_id = WorkerThreadPool::thread_enter_unlock_allowance_zone(&singleton->mutex);
+	uint32_t allowance_id = WorkerThreadPool::thread_enter_unlock_allowance_zone(singleton->mutex);
 	r_error = script->reload(true);
 	WorkerThreadPool::thread_exit_unlock_allowance_zone(allowance_id);
 	if (r_error) {