ANR Broadcast TimeOut 超时判断_broacast timeout anr

android-9.0.0_r8

Broadcast超时判断

前台的“串行广播消息”必须在10秒内处理完毕，后台的“串行广播消息”必须在60秒内处理完毕，每派发串行广播消息到一个接收器，都抛出定时消息BROADCAST_TIMEOUT_MSG，如果定时消息响应了，则说明发生了ANR。

发送BROADCAST_INTENT_MSG处理广播

ContextImpl.broadcastIntent -> AMS.broadcastIntent -> AMS.broadcastIntentLocked -> BroadcastQueue.scheduleBroadcastsLocked

BroadcastHandler采用“ActivityManager”线程的Looper

BroadcastHandler使用的是AMS的Looper，真正派发广播的是AMS线程(system_server进程中的ActivityManager线程)，往AMS线程的消息队列发送BROADCAST_INTENT_MSG消息

mHandlerThread = new ServiceThread(TAG,
                THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
        mHandlerThread.start();
        mHandler = new MainHandler(mHandlerThread.getLooper());
        //... ... ... ...
        mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
                "foreground", BROADCAST_FG_TIMEOUT, false);
        mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
                "background", BROADCAST_BG_TIMEOUT, true);
        mBroadcastQueues[0] = mFgBroadcastQueue;
        mBroadcastQueues[1] = mBgBroadcastQueue;
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BroadcastHandler处理BROADCAST_INTENT_MSG消息

processNextBroadcast 派发广播消息最为核心的函数

其实该版本这里转了一道，processNextBroadcast 跳到 processNextBroadcastLocked 方法
通过调用 processNextBroadcastLocked 来处理广播；其流程为先处理并行广播，再处理当前有序广播，最后获取并处理下条有序广播。

处理并行广播消息

• deliverToRegisteredReceiverLocked 分发广播给已注册的 receiver

处理阻塞的广播消息

有时候会存在一个广播消息派发不出去的情况，这个广播消息会保存在mPendingBroadcast变量中。新一轮的派发启动时，会判断接收该消息的进程是否还活着， 如果接收进程还活着，那么就继续等待。否则，就放弃这个广播消息

处理当前有序广播消息

boolean looped = false;

do {
    //。。。。。。 。。。。。。
    int numReceivers = (r.receivers != null) ? r.receivers.size() : 0;
    if (mService.mProcessesReady && r.dispatchTime > 0) {
        long now = SystemClock.uptimeMillis();
        if ((numReceivers > 0) &&
                (now > r.dispatchTime + (2*mTimeoutPeriod*numReceivers))) {
            Slog.w(TAG, "Hung broadcast ["
                    + mQueueName + "] discarded after timeout failure:"
                    + " now=" + now
                    + " dispatchTime=" + r.dispatchTime
                    + " startTime=" + r.receiverTime
                    + " intent=" + r.intent
                    + " numReceivers=" + numReceivers
                    + " nextReceiver=" + r.nextReceiver
                    + " state=" + r.state);
            broadcastTimeoutLocked(false); // forcibly finish this broadcast
            forceReceive = true;
            r.state = BroadcastRecord.IDLE;
        }
    }
    //。。。。。。 。。。。。。
    if (r.receivers == null || r.nextReceiver >= numReceivers
            || r.resultAbort || forceReceive) {
        // No more receivers for this broadcast!  Send the final
        // result if requested...
        if (r.resultTo != null) {
            try {
                if (DEBUG_BROADCAST) Slog.i(TAG_BROADCAST,
                        "Finishing broadcast [" + mQueueName + "] "
                        + r.intent.getAction() + " app=" + r.callerApp);
                performReceiveLocked(r.callerApp, r.resultTo,
                    new Intent(r.intent), r.resultCode,
                    r.resultData, r.resultExtras, false, false, r.userId);
                // Set this to null so that the reference
                // (local and remote) isn't kept in the mBroadcastHistory.
                r.resultTo = null;
            } catch (RemoteException e) {
                r.resultTo = null;
                Slog.w(TAG, "Failure ["
                        + mQueueName + "] sending broadcast result of "
                        + r.intent, e);

            }
        }

        if (DEBUG_BROADCAST) Slog.v(TAG_BROADCAST, "Cancelling BROADCAST_TIMEOUT_MSG");
        cancelBroadcastTimeoutLocked();
        // 。。。。。。 。。。。。。
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• numReceivers 获取所有该广播所有的接收者
• 判断 broadcastTimeoutLocked 当广播处理时间超时，则强制结束这条广播，第一个ANR监测
• performReceiveLocked 处理广播消息消息
• cancelBroadcastTimeoutLocked() 串行广播消息处理完毕，移除 BROADCAST_TIMEOUT_MSG 消息

获取下条有序广播

• 获取下条有序广播，Handler设置超时消息BROADCAST_TIMEOUT_MSG，串行广播消息的第二个ANR监测机制
  

Broadcast 超时判断

1、(numReceivers > 0) && (now > r.dispatchTime + (2mTimeoutPeriodnumReceivers))

numReceivers 广播接收者不为空；
now = SystemClock.uptimeMillis() 获取当前时间；
r.dispatchTime 表示这一系列广播消息开始派发的时间；
mTimeoutPeriod 由当前BroadcastQueue的类型决定(forground为10秒，background为60秒)

2、获取下条有序广播，setBroadcastTimeoutLocked设置超时BROADCAST_TIMEOUT_MSG消息

• timeoutTime = r.receiverTime + mTimeoutPeriod 设置超时时间
• 响应 BroadcastHandler 消息 BROADCAST_TIMEOUT_MSG
• 

超时响应执行broadcastTimeoutLocked

1、fromMsg = true，设置mPendingBroadcastTimeoutMessage

2、fromMsg = true，当系统还没有准备就绪时，广播处理流程中不存在广播超时

3、fromMsg = true，如果当前正在执行的receiver没有超时，则重新设置广播超时

4、广播已经处理完成，但需要等待已启动service执行完成。当等待足够时间，则处理下一条广播。

5、r.anrCount++：当前BroadcastRecord的anr次数加1；app = mService.mPidsSelfLocked.get(bf.receiverList.pid)：查询App进程；anrMessage：ANR Log信息；finishReceiverLocked、scheduleBroadcastsLocked：已经超时，则结束对当前接收器，开始新一轮调度；mHandler.post(new AppNotResponding(app, anrMessage))：使用AppNotResponding输出Log

AppNotResponding输出Log

和ANR service TimeOut 超时判断使用AppErrors.appNotResponding最终输出Log

何时清除超时消息BROADCAST_TIMEOUT_MSG

processNextBroadcastLocked中处理串行广播完成时，调用cancelBroadcastTimeoutLocked方法移除BROADCAST_TIMEOUT_MSG消息

感谢

ANR机制以及问题分析
理解Android ANR的触发原理
Android Broadcast广播机制分析
Android深入四大组件（四）广播的注册、发送和接收过程