RpcSession attaches/detaches JVM for Java thread

If javaAttachThread / javaDetachThread exists, run them before
and after the while loop in join. This ensures the
Java thread is attached / detached appropriately for
binder threads that handles RPC calls.

Test: run aservice on Java services
Bug: 190450693
Change-Id: I23f171dd1e08dfacfbbb46ecc9564cbf42d6f353

1 files changed, 46 insertions, 0 deletions

diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index ee5e8bb5bb..bdf1bbef02 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -18,13 +18,16 @@
 
 #include <binder/RpcSession.h>
 
+#include <dlfcn.h>
 #include <inttypes.h>
 #include <poll.h>
+#include <pthread.h>
 #include <unistd.h>
 
 #include <string_view>
 
 #include <android-base/macros.h>
+#include <android_runtime/threads.h>
 #include <binder/Parcel.h>
 #include <binder/RpcServer.h>
 #include <binder/Stability.h>
@@ -274,10 +277,53 @@ RpcSession::PreJoinSetupResult RpcSession::preJoinSetup(base::unique_fd fd) {
     };
 }
 
+namespace {
+// RAII object for attaching / detaching current thread to JVM if Android Runtime exists. If
+// Android Runtime doesn't exist, no-op.
+class JavaThreadAttacher {
+public:
+    JavaThreadAttacher() {
+        // Use dlsym to find androidJavaAttachThread because libandroid_runtime is loaded after
+        // libbinder.
+        static auto attachFn = reinterpret_cast<decltype(&androidJavaAttachThread)>(
+                dlsym(RTLD_DEFAULT, "androidJavaAttachThread"));
+        if (attachFn == nullptr) return;
+
+        char buf[16];
+        const char* threadName = "UnknownRpcSessionThread"; // default thread name
+        if (0 == pthread_getname_np(pthread_self(), buf, sizeof(buf))) {
+            threadName = buf;
+        }
+        LOG_RPC_DETAIL("Attaching current thread %s to JVM", threadName);
+        LOG_ALWAYS_FATAL_IF(!attachFn(threadName), "Cannot attach thread %s to JVM", threadName);
+        mAttached = true;
+    }
+    ~JavaThreadAttacher() {
+        if (!mAttached) return;
+        static auto detachFn = reinterpret_cast<decltype(&androidJavaDetachThread)>(
+                dlsym(RTLD_DEFAULT, "androidJavaDetachThread"));
+        LOG_ALWAYS_FATAL_IF(detachFn == nullptr,
+                            "androidJavaAttachThread exists but androidJavaDetachThread doesn't");
+
+        LOG_RPC_DETAIL("Detaching current thread from JVM");
+        if (detachFn()) {
+            mAttached = false;
+        } else {
+            ALOGW("Unable to detach current thread from JVM");
+        }
+    }
+
+private:
+    DISALLOW_COPY_AND_ASSIGN(JavaThreadAttacher);
+    bool mAttached = false;
+};
+} // namespace
+
 void RpcSession::join(sp<RpcSession>&& session, PreJoinSetupResult&& setupResult) {
     sp<RpcConnection>& connection = setupResult.connection;
 
     if (setupResult.status == OK) {
+        JavaThreadAttacher javaThreadAttacher;
         while (true) {
             status_t status = session->state()->getAndExecuteCommand(connection, session,
                                                                      RpcState::CommandType::ANY);