[binder] Implicitly initialize the binder pool (#27261)

examples/android/binder/java/io/grpc/binder/cpp/exampleserver/native.cc

@@ -58,7 +58,6 @@ Java_io_grpc_binder_cpp_exampleserver_ExportedEndpointService_init_1grpc_1server
   grpc::ServerBuilder server_builder;
   server_builder.RegisterService(&service);
 
-  grpc_endpoint_binder_pool_init();
   server_builder.AddListeningPort(
       "binder://example.service",
       grpc::experimental::BinderServerCredentials());

src/core/ext/transport/binder/server/binder_server.cc

@@ -47,34 +47,40 @@ void RemoveEndpointBinder(const std::string& service) {
 }  // namespace experimental
 }  // namespace grpc
 
-grpc_core::Mutex* g_endpoint_binder_pool_mu = nullptr;
-absl::flat_hash_map<std::string, void*>* g_endpoint_binder_pool = nullptr;
+static absl::flat_hash_map<std::string, void*>* g_endpoint_binder_pool =
+    nullptr;
 
-void grpc_endpoint_binder_pool_init() {
-  g_endpoint_binder_pool_mu = new grpc_core::Mutex();
-  g_endpoint_binder_pool = new absl::flat_hash_map<std::string, void*>();
-}
+namespace {
 
-void grpc_endpoint_binder_pool_shutdown() {
-  g_endpoint_binder_pool_mu->Lock();
-  delete g_endpoint_binder_pool;
-  g_endpoint_binder_pool_mu->Unlock();
-  delete g_endpoint_binder_pool_mu;
+grpc_core::Mutex* GetBinderPoolMutex() {
+  static grpc_core::Mutex* mu = new grpc_core::Mutex();
+  return mu;
 }
 
+}  // namespace
+
 void grpc_add_endpoint_binder(const std::string& service,
                               void* endpoint_binder) {
-  grpc_core::MutexLock lock(g_endpoint_binder_pool_mu);
+  grpc_core::MutexLock lock(GetBinderPoolMutex());
+  if (g_endpoint_binder_pool == nullptr) {
+    g_endpoint_binder_pool = new absl::flat_hash_map<std::string, void*>();
+  }
   (*g_endpoint_binder_pool)[service] = endpoint_binder;
 }
 
 void grpc_remove_endpoint_binder(const std::string& service) {
-  grpc_core::MutexLock lock(g_endpoint_binder_pool_mu);
+  grpc_core::MutexLock lock(GetBinderPoolMutex());
+  if (g_endpoint_binder_pool == nullptr) {
+    return;
+  }
   g_endpoint_binder_pool->erase(service);
 }
 
 void* grpc_get_endpoint_binder(const std::string& service) {
-  grpc_core::MutexLock lock(g_endpoint_binder_pool_mu);
+  grpc_core::MutexLock lock(GetBinderPoolMutex());
+  if (g_endpoint_binder_pool == nullptr) {
+    return nullptr;
+  }
   auto iter = g_endpoint_binder_pool->find(service);
   return iter == g_endpoint_binder_pool->end() ? nullptr : iter->second;
 }

src/core/ext/transport/binder/server/binder_server.h

@@ -41,14 +41,6 @@ void RemoveEndpointBinder(const std::string& service);
 }  // namespace experimental
 }  // namespace grpc
 
-extern grpc_core::Mutex* g_endpoint_binder_pool_mu;
-extern absl::flat_hash_map<std::string, void*>* g_endpoint_binder_pool;
-
-// TODO(waynetu): Can these two functions be called in grpc_init() and
-// grpc_shutdown()?
-void grpc_endpoint_binder_pool_init();
-void grpc_endpoint_binder_pool_shutdown();
-
 void grpc_add_endpoint_binder(const std::string& service,
                               void* endpoint_binder);
 void grpc_remove_endpoint_binder(const std::string& service);

test/core/transport/binder/end2end/binder_server_test.cc

@@ -89,14 +89,8 @@ class BinderServerTest : public ::testing::Test {
   ~BinderServerTest() override {
     delete grpc_binder::end2end_testing::g_transaction_processor;
   }
-  static void SetUpTestSuite() {
-    grpc_init();
-    grpc_endpoint_binder_pool_init();
-  }
-  static void TearDownTestSuite() {
-    grpc_endpoint_binder_pool_shutdown();
-    grpc_shutdown();
-  }
+  static void SetUpTestSuite() { grpc_init(); }
+  static void TearDownTestSuite() { grpc_shutdown(); }
 };
 
 #ifndef GPR_ANDROID