Dynamically stop lazy services
Services can choose to register with the new LazyServiceRegistrar.
ServiceManager perpetually checks the reference counts of services
registered in this way. If ServiceManager detects that a service no
longer has any clients, it will notify the LazyServiceRegistrar, which
will attempt to shut down the service.
Bug: 143108344
Test: aidl_lazy_test
Change-Id: Ic01981b767ab4402e7aecdf1cdf9ed64df1f5af4
diff --git a/libs/binder/LazyServiceRegistrar.cpp b/libs/binder/LazyServiceRegistrar.cpp
new file mode 100644
index 0000000..dc9482c
--- /dev/null
+++ b/libs/binder/LazyServiceRegistrar.cpp
@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "AidlLazyServiceRegistrar"
+
+#include <binder/LazyServiceRegistrar.h>
+#include <binder/IPCThreadState.h>
+#include <binder/IServiceManager.h>
+#include <android/os/BnClientCallback.h>
+#include <android/os/IServiceManager.h>
+#include <utils/Log.h>
+
+namespace android {
+namespace binder {
+namespace internal {
+
+using AidlServiceManager = android::os::IServiceManager;
+
+class ClientCounterCallback : public ::android::os::BnClientCallback {
+public:
+ ClientCounterCallback() : mNumConnectedServices(0) {}
+
+ bool registerService(const sp<IBinder>& service, const std::string& name,
+ bool allowIsolated, int dumpFlags);
+
+protected:
+ Status onClients(const sp<IBinder>& service, bool clients) override;
+
+private:
+ /**
+ * Unregisters all services that we can. If we can't unregister all, re-register other
+ * services.
+ */
+ void tryShutdown();
+
+ /**
+ * Counter of the number of services that currently have at least one client.
+ */
+ size_t mNumConnectedServices;
+
+ struct Service {
+ sp<IBinder> service;
+ std::string name;
+ bool allowIsolated;
+ int dumpFlags;
+ };
+ /**
+ * Number of services that have been registered.
+ */
+ std::vector<Service> mRegisteredServices;
+};
+
+bool ClientCounterCallback::registerService(const sp<IBinder>& service, const std::string& name,
+ bool allowIsolated, int dumpFlags) {
+ auto manager = interface_cast<AidlServiceManager>(
+ ProcessState::self()->getContextObject(nullptr));
+
+ ALOGI("Registering service %s", name.c_str());
+
+ if (!manager->addService(name.c_str(), service, allowIsolated, dumpFlags).isOk()) {
+ ALOGE("Failed to register service %s", name.c_str());
+ return false;
+ }
+
+ if (!manager->registerClientCallback(name, service, this).isOk())
+ {
+ ALOGE("Failed to add client callback for service %s", name.c_str());
+ return false;
+ }
+
+ mRegisteredServices.push_back({service, name, allowIsolated, dumpFlags});
+
+ return true;
+}
+
+/**
+ * onClients is oneway, so no need to worry about multi-threading. Note that this means multiple
+ * invocations could occur on different threads however.
+ */
+Status ClientCounterCallback::onClients(const sp<IBinder>& service, bool clients) {
+ if (clients) {
+ mNumConnectedServices++;
+ } else {
+ mNumConnectedServices--;
+ }
+
+ ALOGI("Process has %zu (of %zu available) client(s) in use after notification %s has clients: %d",
+ mNumConnectedServices, mRegisteredServices.size(),
+ String8(service->getInterfaceDescriptor()).string(), clients);
+
+ if (mNumConnectedServices == 0) {
+ tryShutdown();
+ }
+
+ return Status::ok();
+}
+
+void ClientCounterCallback::tryShutdown() {
+ ALOGI("Trying to shut down the service. No clients in use for any service in process.");
+
+ // This makes the same assumption as IServiceManager.cpp. Could dedupe if used in more places.
+ auto manager = interface_cast<AidlServiceManager>(
+ ProcessState::self()->getContextObject(nullptr));
+
+ auto unRegisterIt = mRegisteredServices.begin();
+ for (; unRegisterIt != mRegisteredServices.end(); ++unRegisterIt) {
+ auto& entry = (*unRegisterIt);
+
+ bool success = manager->tryUnregisterService(entry.name, entry.service).isOk();
+
+ if (!success) {
+ ALOGI("Failed to unregister service %s", entry.name.c_str());
+ break;
+ }
+ }
+
+ if (unRegisterIt == mRegisteredServices.end()) {
+ ALOGI("Unregistered all clients and exiting");
+ exit(EXIT_SUCCESS);
+ }
+
+ for (auto reRegisterIt = mRegisteredServices.begin(); reRegisterIt != unRegisterIt;
+ reRegisterIt++) {
+ auto& entry = (*reRegisterIt);
+
+ // re-register entry
+ if (!registerService(entry.service, entry.name, entry.allowIsolated, entry.dumpFlags)) {
+ // Must restart. Otherwise, clients will never be able to get a hold of this service.
+ ALOGE("Bad state: could not re-register services");
+ }
+ }
+}
+
+} // namespace internal
+
+LazyServiceRegistrar::LazyServiceRegistrar() {
+ mClientCC = std::make_shared<internal::ClientCounterCallback>();
+}
+
+LazyServiceRegistrar& LazyServiceRegistrar::getInstance() {
+ static auto registrarInstance = new LazyServiceRegistrar();
+ return *registrarInstance;
+}
+
+status_t LazyServiceRegistrar::registerService(const sp<IBinder>& service, const std::string& name,
+ bool allowIsolated, int dumpFlags) {
+ if (!mClientCC->registerService(service, name, allowIsolated, dumpFlags)) {
+ return UNKNOWN_ERROR;
+ }
+ return OK;
+}
+
+} // namespace hardware
+} // namespace android
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