Thread might actually be detached, so need to handle that

zerotier · May 21, 2024 · e32fecd · e32fecd
1 parent dca77cb
commit e32fecd
Showing 1 changed file with 51 additions and 1 deletion.
diff --git a/java/jni/com_zerotierone_sdk_Node.cpp b/java/jni/com_zerotierone_sdk_Node.cpp
@@ -111,6 +111,44 @@ namespace {
  bool finishInitializing();
  };
 
+ //
+ // RAII construct for calling AttachCurrentThread and DetachCurrent automatically
+ //
+ struct ScopedJNIThreadAttacher {
+
+ JavaVM *jvm;
+ JNIEnv **env_p;
+ jint getEnvRet;
+
+ ScopedJNIThreadAttacher(JavaVM *jvmIn, JNIEnv **env_pIn, jint getEnvRetIn) :
+ jvm(jvmIn),
+ env_p(env_pIn),
+ getEnvRet(getEnvRetIn) {
+
+ if (getEnvRet != JNI_EDETACHED) {
+ return;
+ }
+
+ jint attachCurrentThreadRet;
+ if ((attachCurrentThreadRet = jvm->AttachCurrentThread(env_p, NULL)) != JNI_OK) {
+ LOGE("Error calling AttachCurrentThread: %d", attachCurrentThreadRet);
+ assert(false && "Error calling AttachCurrentThread");
+ }
+ }
+
+ ~ScopedJNIThreadAttacher() {
+
+ if (getEnvRet != JNI_EDETACHED) {
+ return;
+ }
+
+ jint detachCurrentThreadRet;
+ if ((detachCurrentThreadRet = jvm->DetachCurrentThread()) != JNI_OK) {
+ LOGE("Error calling DetachCurrentThread: %d", detachCurrentThreadRet);
+ assert(false && "Error calling DetachCurrentThread");
+ }
+ }
+ };
 
  /*
  * This must return 0 on success. It can return any OS-dependent error code
@@ -197,11 +235,23 @@ namespace {
 
  jint getEnvRet;
  assert(ref->jvm);
- if ((getEnvRet = ref->jvm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6)) != JNI_OK) {
+ getEnvRet = ref->jvm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6);
+
+ if (!(getEnvRet == JNI_OK || getEnvRet == JNI_EDETACHED)) {
  LOGE("Error calling GetEnv: %d", getEnvRet);
  assert(false && "Error calling GetEnv");
  }
 
+ //
+ // Thread might actually be detached.
+ //
+ // e.g:
+ // https://github.com/zerotier/ZeroTierOne/blob/91e7ce87f09ac1cfdeaf6ff22c3cedcd93574c86/node/Switch.cpp#L519
+ //
+ // Make sure to attach if needed
+ //
+ ScopedJNIThreadAttacher attacher{ref->jvm, &env, getEnvRet};
+
  if (env->ExceptionCheck()) {
  LOGE("Unhandled pending exception");
  return;