Broadcast（五）ANR

本文关注11、19、21、24、34

11 设置超时

// setBroadcastTimeoutLocked()把mPendingBroadcastTimeoutMessage设置为true
// 所以只会进入一次
if (! mPendingBroadcastTimeoutMessage) {
    long timeoutTime = r.receiverTime + mTimeoutPeriod;
    setBroadcastTimeoutLocked(timeoutTime);
}

final void setBroadcastTimeoutLocked(long timeoutTime) {
    if (! mPendingBroadcastTimeoutMessage) {
        Message msg = mHandler.obtainMessage(BROADCAST_TIMEOUT_MSG, this);
        // 延迟timeoutTime给BroadcastHandler发送一条BROADCAST_TIMEOUT_MSG消息
        mHandler.sendMessageAtTime(msg, timeoutTime);
        mPendingBroadcastTimeoutMessage = true;
    }
}

34 取消超时

final void cancelBroadcastTimeoutLocked() {
    if (mPendingBroadcastTimeoutMessage) {
        mHandler.removeMessages(BROADCAST_TIMEOUT_MSG, this);
        // 还原mPendingBroadcastTimeoutMessage
        mPendingBroadcastTimeoutMessage = false;
    }
}

19

private final class BroadcastHandler extends Handler {
    public BroadcastHandler(Looper looper) {
        super(looper, null, true);
    }

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case BROADCAST_INTENT_MSG: {
                processNextBroadcast(true);
            } break;
            case BROADCAST_TIMEOUT_MSG: {
                synchronized (mService) {
                    broadcastTimeoutLocked(true);
                }
            } break;
            ...
        }
    }
};

上面说只有第一个receiver会设置超时，最后一个receiver执行完才会取消超时。那么假如有ABC3个静态注册的receiver，它们耗时都是6s，然后发送一个前台广播，那么要执行完B就需要12s，我们知道前台广播是10s超时，所以就会进入broadcastTimeoutLocked()，那么会弹出ANR么？接着看

21或24

final void broadcastTimeoutLocked(boolean fromMsg) {
    if (fromMsg) {
        // 不管怎样，先还原mPendingBroadcastTimeoutMessage
        mPendingBroadcastTimeoutMessage = false;
    }

    if (mOrderedBroadcasts.size() == 0) {
        return;
    }

    long now = SystemClock.uptimeMillis();
    BroadcastRecord r = mOrderedBroadcasts.get(0);
    if (fromMsg) {
        if (mService.mDidDexOpt) {
            // Delay timeouts until dexopt finishes.
            mService.mDidDexOpt = false;
            long timeoutTime = SystemClock.uptimeMillis() + mTimeoutPeriod;
            setBroadcastTimeoutLocked(timeoutTime);
            return;
        }
        if (!mService.mProcessesReady) {
            // Only process broadcast timeouts if the system is ready. That way
            // PRE_BOOT_COMPLETED broadcasts can't timeout as they are intended
            // to do heavy lifting for system up.
            return;
        }

        long timeoutTime = r.receiverTime + mTimeoutPeriod;

        // 所以重点是这个判断，虽然会进入这个broadcastTimeoutLocked()
        // 但是每个receiver的receiverTime是在processNextBroadcast分配的
        // r.receiverTime = SystemClock.uptimeMillis()
        // 我还是不明白为什么不在通知receiver前先去掉超时，然后重新设置超时
        if (timeoutTime > now) {
            // We can observe premature timeouts because we do not cancel and reset the
            // broadcast timeout message after each receiver finishes.  Instead, we set up
            // an initial timeout then kick it down the road a little further as needed
            // when it expires.
            // 设置超时
            setBroadcastTimeoutLocked(timeoutTime);
            return;
        }
    }

    BroadcastRecord br = mOrderedBroadcasts.get(0);
    if (br.state == BroadcastRecord.WAITING_SERVICES) {
        // In this case the broadcast had already finished, but we had decided to wait
        // for started services to finish as well before going on.  So if we have actually
        // waited long enough time timeout the broadcast, let's give up on the whole thing
        // and just move on to the next.
        br.curComponent = null;
        br.state = BroadcastRecord.IDLE;
        processNextBroadcast(false);
        return;
    }
    r.receiverTime = now;
    r.anrCount++;

    // Current receiver has passed its expiration date.
    if (r.nextReceiver <= 0) {
        return;
    }

    ProcessRecord app = null;
    String anrMessage = null;

    Object curReceiver = r.receivers.get(r.nextReceiver-1);
    logBroadcastReceiverDiscardLocked(r);
    if (curReceiver instanceof BroadcastFilter) {
        BroadcastFilter bf = (BroadcastFilter)curReceiver;
        if (bf.receiverList.pid != 0
                && bf.receiverList.pid != ActivityManagerService.MY_PID) {
            synchronized (mService.mPidsSelfLocked) {
                app = mService.mPidsSelfLocked.get(
                        bf.receiverList.pid);
            }
        }
    } else {
        app = r.curApp;
    }

    if (app != null) {
        anrMessage = "Broadcast of " + r.intent.toString();
    }

    if (mPendingBroadcast == r) {
        mPendingBroadcast = null;
    }

    // 超时了，不继续等待app通知，直接继续下一个receiver
    // Move on to the next receiver.
    finishReceiverLocked(r, r.resultCode, r.resultData,
            r.resultExtras, r.resultAbort, false);
    scheduleBroadcastsLocked();
    
    // ANR
    if (anrMessage != null) {
        // Post the ANR to the handler since we do not want to process ANRs while
        // potentially holding our lock.
        mHandler.post(new AppNotResponding(app, anrMessage));
    }
}

ANR

final ActivityManagerService mService;

private final class AppNotResponding implements Runnable {
    private final ProcessRecord mApp;
    private final String mAnnotation;

    public AppNotResponding(ProcessRecord app, String annotation) {
        mApp = app;
        mAnnotation = annotation;
    }

    @Override
    public void run() {
        mService.appNotResponding(mApp, null, null, false, mAnnotation);
    }
}

进入AMS.appNotResponding()，参考[Service（二）ANR]