3055 class CountStackFramesTC : public ThreadClosure {

  3056   int _count;

  3057   bool _suspended;

  3058  public:

  3059   CountStackFramesTC() : _count(0), _suspended(false) {}

  3060   virtual void do_thread(Thread* thread) {

  3061     JavaThread* jt = (JavaThread*)thread;

  3062     if (!jt->is_external_suspend()) {

  3063       // To keep same behavior we fail this operation,

  3064       // even if it would work perfectly.

  3065       return;

  3066     }

  3067     _suspended = true;

  3068      // Count all java activation, i.e., number of vframes.

  3069     for (vframeStream vfst(jt); !vfst.at_end(); vfst.next()) {

  3070       // Native frames are not counted.

  3071       if (!vfst.method()->is_native()) _count++;

  3072     }

  3073   }

  3074   int count() { return _count; }

  3075   int suspended() { return _suspended; }

  3076 };

  3077 

  3078 JVM_ENTRY(jint, JVM_CountStackFrames(JNIEnv* env, jobject jthread))

  3079   JVMWrapper("JVM_CountStackFrames");

  3080 

  3081   ThreadsListHandle tlh(thread);

  3082   JavaThread* receiver = NULL;

  3083   bool is_alive = tlh.cv_internal_thread_to_JavaThread(jthread, &receiver, NULL);

  3084   if (is_alive) {

  3085     // jthread refers to a live JavaThread.

  3086     CountStackFramesTC csf;

  3087     Handshake::execute(&csf, receiver);

  3088     if (!csf.suspended()) {

  3089       THROW_MSG_0(vmSymbols::java_lang_IllegalThreadStateException(),

  3090                   "this thread is not suspended");

  3091     }

  3092     return csf.count();

  3093   }

  3094   // Implied else: if JavaThread is not alive simply return a count of 0.

  3095   return 0;

  3096 JVM_END

  3097 

  3098