Add thread safety annotations (#26935)

src/core/lib/surface/init.cc

@@ -64,20 +64,18 @@ extern void grpc_register_built_in_plugins(void);
 
 static gpr_once g_basic_init = GPR_ONCE_INIT;
 static grpc_core::Mutex* g_init_mu;
-static int g_initializations;
+static int g_initializations ABSL_GUARDED_BY(g_init_mu) = 0;
 static grpc_core::CondVar* g_shutting_down_cv;
-static bool g_shutting_down;
+static bool g_shutting_down ABSL_GUARDED_BY(g_init_mu) = false;
 
 static void do_basic_init(void) {
   gpr_log_verbosity_init();
   g_init_mu = new grpc_core::Mutex();
   g_shutting_down_cv = new grpc_core::CondVar();
-  g_shutting_down = false;
   grpc_register_built_in_plugins();
   grpc_cq_global_init();
   grpc_core::grpc_executor_global_init();
   gpr_time_init();
-  g_initializations = 0;
 }
 
 static bool append_filter(grpc_channel_stack_builder* builder, void* arg) {
@@ -167,7 +165,8 @@ void grpc_init(void) {
   GRPC_API_TRACE("grpc_init(void)", 0, ());
 }
 
-void grpc_shutdown_internal_locked(void) {
+void grpc_shutdown_internal_locked(void)
+    ABSL_EXCLUSIVE_LOCKS_REQUIRED(g_init_mu) {
   int i;
   {
     grpc_core::ExecCtx exec_ctx(0);