Add waitForService to AIDL.
Eye towards:
- avoiding while(true) getService loops
- need it to make AIDL dynamic HALs
- need it for feature parity w/ HIDL
Bug: 136027762
Test: use in AIDL unit test
Change-Id: I2981eb4ebecff8c4519e09b7dcca51892dfd528d
diff --git a/libs/binder/IServiceManager.cpp b/libs/binder/IServiceManager.cpp
index 74f1f47..715a460 100644
--- a/libs/binder/IServiceManager.cpp
+++ b/libs/binder/IServiceManager.cpp
@@ -18,6 +18,7 @@
#include <binder/IServiceManager.h>
+#include <android/os/BnServiceCallback.h>
#include <android/os/IServiceManager.h>
#include <utils/Log.h>
#include <binder/IPCThreadState.h>
@@ -212,6 +213,64 @@
return res;
}
+ sp<IBinder> waitForService(const String16& name16) override {
+ class Waiter : public android::os::BnServiceCallback {
+ Status onRegistration(const std::string& /*name*/,
+ const sp<IBinder>& binder) override {
+ std::unique_lock<std::mutex> lock(mMutex);
+ mBinder = binder;
+ lock.unlock();
+ mCv.notify_one();
+ return Status::ok();
+ }
+ public:
+ sp<IBinder> mBinder;
+ std::mutex mMutex;
+ std::condition_variable mCv;
+ };
+
+ const std::string name = String8(name16).c_str();
+
+ sp<IBinder> out;
+ if(!mTheRealServiceManager->checkService(name, &out).isOk()) {
+ return nullptr;
+ }
+ if(out != nullptr) return out;
+
+ sp<Waiter> waiter = new Waiter;
+ if (!mTheRealServiceManager->registerForNotifications(
+ name, waiter).isOk()) {
+ return nullptr;
+ }
+
+ while(true) {
+ {
+ std::unique_lock<std::mutex> lock(waiter->mMutex);
+ using std::literals::chrono_literals::operator""s;
+ waiter->mCv.wait_for(lock, 1s, [&] {
+ return waiter->mBinder != nullptr;
+ });
+ if (waiter->mBinder != nullptr) return waiter->mBinder;
+ }
+
+ // Handle race condition for lazy services. Here is what can happen:
+ // - the service dies (not processed by init yet).
+ // - sm processes death notification.
+ // - sm gets checkService and calls init to start service.
+ // - init gets the start signal, but the service already appears
+ // started, so it does nothing.
+ // - init gets death signal, but doesn't know it needs to restart
+ // the service
+ // - we need to request service again to get it to start
+ if(!mTheRealServiceManager->checkService(name, &out).isOk()) {
+ return nullptr;
+ }
+ if(out != nullptr) return out;
+
+ ALOGW("Waited one second for %s", name.c_str());
+ }
+ }
+
private:
sp<AidlServiceManager> mTheRealServiceManager;
};
diff --git a/libs/binder/include/binder/IServiceManager.h b/libs/binder/include/binder/IServiceManager.h
index 30786fa..8ae860d 100644
--- a/libs/binder/include/binder/IServiceManager.h
+++ b/libs/binder/include/binder/IServiceManager.h
@@ -71,11 +71,24 @@
*/
// NOLINTNEXTLINE(google-default-arguments)
virtual Vector<String16> listServices(int dumpsysFlags = DUMP_FLAG_PRIORITY_ALL) = 0;
+
+ /**
+ * Efficiently wait for a service.
+ *
+ * Returns nullptr only for permission problem or fatal error.
+ */
+ virtual sp<IBinder> waitForService(const String16& name) = 0;
};
sp<IServiceManager> defaultServiceManager();
template<typename INTERFACE>
+sp<INTERFACE> waitForService(const String16& name) {
+ const sp<IServiceManager> sm = defaultServiceManager();
+ return interface_cast<INTERFACE>(sm->waitForService(name));
+}
+
+template<typename INTERFACE>
status_t getService(const String16& name, sp<INTERFACE>* outService)
{
const sp<IServiceManager> sm = defaultServiceManager();