线程-sleep,wait及interrupt

2016-08-24

Thread.sleep

###　JVM_Sleep

jvm.cpp

JVM_ENTRY(void, JVM_Sleep(JNIEnv* env, jclass threadClass, jlong millis))
  JVMWrapper("JVM_Sleep");

  if (millis < 0) {
    THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
  }

  if (Thread::is_interrupted (THREAD, true) && !HAS_PENDING_EXCEPTION) {
    THROW_MSG(vmSymbols::java_lang_InterruptedException(), "sleep interrupted");
  }

  // Save current thread state and restore it at the end of this block.
  // And set new thread state to SLEEPING.
  JavaThreadSleepState jtss(thread);

  HS_DTRACE_PROBE1(hotspot, thread__sleep__begin, millis);

  if (millis == 0) {
    // When ConvertSleepToYield is on, this matches the classic VM implementation of
    // JVM_Sleep. Critical for similar threading behaviour (Win32)
    // It appears that in certain GUI contexts, it may be beneficial to do a short sleep
    // for SOLARIS
    if (ConvertSleepToYield) {
      os::yield();
    } else {
      ThreadState old_state = thread->osthread()->get_state();
      thread->osthread()->set_state(SLEEPING);
	  // 线程在 sleep 过程中不响应中断
      os::sleep(thread, MinSleepInterval, false);
      thread->osthread()->set_state(old_state);
    }
  } else {
    ThreadState old_state = thread->osthread()->get_state();
    thread->osthread()->set_state(SLEEPING);
    if (os::sleep(thread, millis, true) == OS_INTRPT) {
	   // 线程被中断了，
      // An asynchronous exception (e.g., ThreadDeathException) could have been thrown on
      // us while we were sleeping. We do not overwrite those.
      if (!HAS_PENDING_EXCEPTION) {
        HS_DTRACE_PROBE1(hotspot, thread__sleep__end,1);
        // TODO-FIXME: THROW_MSG returns which means we will not call set_state()
        // to properly restore the thread state.  That's likely wrong.
		// 抛出线程中断异常 InterruptedException
        THROW_MSG(vmSymbols::java_lang_InterruptedException(), "sleep interrupted");
      }
    }
    thread->osthread()->set_state(old_state);
  }
  HS_DTRACE_PROBE1(hotspot, thread__sleep__end,0);
JVM_END

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Unsafe类

2016-08-23

Unsafe

unsafe.cpp

// park
UNSAFE_ENTRY(void, Unsafe_Park(JNIEnv *env, jobject unsafe, jboolean isAbsolute, jlong time))
  UnsafeWrapper("Unsafe_Park");
  HS_DTRACE_PROBE3(hotspot, thread__park__begin, thread->parker(), (int) isAbsolute, time);
  JavaThreadParkedState jtps(thread, time != 0);
  thread->parker()->park(isAbsolute != 0, time);
  HS_DTRACE_PROBE1(hotspot, thread__park__end, thread->parker());
UNSAFE_END

// unpark
UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread))
  UnsafeWrapper("Unsafe_Unpark");
  Parker* p = NULL;
  if (jthread != NULL) {
    oop java_thread = JNIHandles::resolve_non_null(jthread);
    if (java_thread != NULL) {
      jlong lp = java_lang_Thread::park_event(java_thread);
      if (lp != 0) {
        // This cast is OK even though the jlong might have been read
        // non-atomically on 32bit systems, since there, one word will
        // always be zero anyway and the value set is always the same
        p = (Parker*)addr_from_java(lp);
      } else {
        // Grab lock if apparently null or using older version of library
        MutexLocker mu(Threads_lock);
        java_thread = JNIHandles::resolve_non_null(jthread);
        if (java_thread != NULL) {
          JavaThread* thr = java_lang_Thread::thread(java_thread);
          if (thr != NULL) {
            p = thr->parker();
            if (p != NULL) { // Bind to Java thread for next time.
              java_lang_Thread::set_park_event(java_thread, addr_to_java(p));
            }
          }
        }
      }
    }
  }
  if (p != NULL) {
    HS_DTRACE_PROBE1(hotspot, thread__unpark, p);
    p->unpark();
  }
UNSAFE_END