1 files changed, 42 insertions, 26 deletions

diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index f83bb5e335..1cd1fd3afd 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -32,6 +32,7 @@
 #include <log/log.h>
 #include <utils/Compat.h>
 
+#include "BuildFlags.h"
 #include "FdTrigger.h"
 #include "RpcSocketAddress.h"
 #include "RpcState.h"
@@ -131,27 +132,27 @@ void RpcServer::setSupportedFileDescriptorTransportModes(
 }
 
 void RpcServer::setRootObject(const sp<IBinder>& binder) {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     mRootObjectFactory = nullptr;
     mRootObjectWeak = mRootObject = binder;
 }
 
 void RpcServer::setRootObjectWeak(const wp<IBinder>& binder) {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     mRootObject.clear();
     mRootObjectFactory = nullptr;
     mRootObjectWeak = binder;
 }
 void RpcServer::setPerSessionRootObject(
         std::function<sp<IBinder>(const void*, size_t)>&& makeObject) {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     mRootObject.clear();
     mRootObjectWeak.clear();
     mRootObjectFactory = std::move(makeObject);
 }
 
 sp<IBinder> RpcServer::getRootObject() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     bool hasWeak = mRootObjectWeak.unsafe_get();
     sp<IBinder> ret = mRootObjectWeak.promote();
     ALOGW_IF(hasWeak && ret == nullptr, "RpcServer root object is freed, returning nullptr");
@@ -159,7 +160,7 @@ sp<IBinder> RpcServer::getRootObject() {
 }
 
 std::vector<uint8_t> RpcServer::getCertificate(RpcCertificateFormat format) {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     return mCtx->getCertificate(format);
 }
 
@@ -168,15 +169,17 @@ static void joinRpcServer(sp<RpcServer>&& thiz) {
 }
 
 void RpcServer::start() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     LOG_ALWAYS_FATAL_IF(mJoinThread.get(), "Already started!");
-    mJoinThread = std::make_unique<std::thread>(&joinRpcServer, sp<RpcServer>::fromExisting(this));
+    mJoinThread =
+            std::make_unique<RpcMaybeThread>(&joinRpcServer, sp<RpcServer>::fromExisting(this));
+    rpcJoinIfSingleThreaded(*mJoinThread);
 }
 
 void RpcServer::join() {
 
     {
-        std::lock_guard<std::mutex> _l(mLock);
+        RpcMutexLockGuard _l(mLock);
         LOG_ALWAYS_FATAL_IF(!mServer.ok(), "RpcServer must be setup to join.");
         LOG_ALWAYS_FATAL_IF(mShutdownTrigger != nullptr, "Already joined");
         mJoinThreadRunning = true;
@@ -204,24 +207,31 @@ void RpcServer::join() {
         LOG_RPC_DETAIL("accept4 on fd %d yields fd %d", mServer.get(), clientFd.get());
 
         {
-            std::lock_guard<std::mutex> _l(mLock);
-            std::thread thread =
-                    std::thread(&RpcServer::establishConnection, sp<RpcServer>::fromExisting(this),
-                                std::move(clientFd), addr, addrLen);
-            mConnectingThreads[thread.get_id()] = std::move(thread);
+            RpcMutexLockGuard _l(mLock);
+            RpcMaybeThread thread = RpcMaybeThread(&RpcServer::establishConnection,
+                                                   sp<RpcServer>::fromExisting(this),
+                                                   std::move(clientFd), addr, addrLen);
+
+            auto& threadRef = mConnectingThreads[thread.get_id()];
+            threadRef = std::move(thread);
+            rpcJoinIfSingleThreaded(threadRef);
         }
     }
     LOG_RPC_DETAIL("RpcServer::join exiting with %s", statusToString(status).c_str());
 
-    {
-        std::lock_guard<std::mutex> _l(mLock);
+    if constexpr (kEnableRpcThreads) {
+        RpcMutexLockGuard _l(mLock);
         mJoinThreadRunning = false;
+    } else {
+        // Multi-threaded builds clear this in shutdown(), but we need it valid
+        // so the loop above exits cleanly
+        mShutdownTrigger = nullptr;
     }
     mShutdownCv.notify_all();
 }
 
 bool RpcServer::shutdown() {
-    std::unique_lock<std::mutex> _l(mLock);
+    RpcMutexUniqueLock _l(mLock);
     if (mShutdownTrigger == nullptr) {
         LOG_RPC_DETAIL("Cannot shutdown. No shutdown trigger installed (already shutdown?)");
         return false;
@@ -232,10 +242,16 @@ bool RpcServer::shutdown() {
     for (auto& [id, session] : mSessions) {
         (void)id;
         // server lock is a more general lock
-        std::lock_guard<std::mutex> _lSession(session->mMutex);
+        RpcMutexLockGuard _lSession(session->mMutex);
         session->mShutdownTrigger->trigger();
     }
 
+    if constexpr (!kEnableRpcThreads) {
+        // In single-threaded mode we're done here, everything else that
+        // needs to happen should be at the end of RpcServer::join()
+        return true;
+    }
+
     while (mJoinThreadRunning || !mConnectingThreads.empty() || !mSessions.empty()) {
         if (std::cv_status::timeout == mShutdownCv.wait_for(_l, std::chrono::seconds(1))) {
             ALOGE("Waiting for RpcServer to shut down (1s w/o progress). Join thread running: %d, "
@@ -263,7 +279,7 @@ bool RpcServer::shutdown() {
 }
 
 std::vector<sp<RpcSession>> RpcServer::listSessions() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     std::vector<sp<RpcSession>> sessions;
     for (auto& [id, session] : mSessions) {
         (void)id;
@@ -273,7 +289,7 @@ std::vector<sp<RpcSession>> RpcServer::listSessions() {
 }
 
 size_t RpcServer::numUninitializedSessions() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     return mConnectingThreads.size();
 }
 
@@ -354,12 +370,12 @@ void RpcServer::establishConnection(sp<RpcServer>&& server, base::unique_fd clie
         }
     }
 
-    std::thread thisThread;
+    RpcMaybeThread thisThread;
     sp<RpcSession> session;
     {
-        std::unique_lock<std::mutex> _l(server->mLock);
+        RpcMutexUniqueLock _l(server->mLock);
 
-        auto threadId = server->mConnectingThreads.find(std::this_thread::get_id());
+        auto threadId = server->mConnectingThreads.find(rpc_this_thread::get_id());
         LOG_ALWAYS_FATAL_IF(threadId == server->mConnectingThreads.end(),
                             "Must establish connection on owned thread");
         thisThread = std::move(threadId->second);
@@ -505,7 +521,7 @@ void RpcServer::onSessionAllIncomingThreadsEnded(const sp<RpcSession>& session)
     LOG_RPC_DETAIL("Dropping session with address %s",
                    base::HexString(id.data(), id.size()).c_str());
 
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     auto it = mSessions.find(id);
     LOG_ALWAYS_FATAL_IF(it == mSessions.end(), "Bad state, unknown session id %s",
                         base::HexString(id.data(), id.size()).c_str());
@@ -519,17 +535,17 @@ void RpcServer::onSessionIncomingThreadEnded() {
 }
 
 bool RpcServer::hasServer() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     return mServer.ok();
 }
 
 unique_fd RpcServer::releaseServer() {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     return std::move(mServer);
 }
 
 status_t RpcServer::setupExternalServer(base::unique_fd serverFd) {
-    std::lock_guard<std::mutex> _l(mLock);
+    RpcMutexLockGuard _l(mLock);
     if (mServer.ok()) {
         ALOGE("Each RpcServer can only have one server.");
         return INVALID_OPERATION;