android/server/Watchdog.java

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server;

import com.android.server.am.ActivityManagerService;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Debug;
import android.os.Handler;
import android.os.Message;
import android.os.Process;
import android.os.SystemClock;
import android.os.SystemProperties;
import android.provider.Settings;
import android.util.Config;
import android.util.EventLog;
import android.util.Log;

import java.util.ArrayList;
import java.util.Calendar;

/** This class calls its monitor every minute. Killing this process if they don't return **/
public class Watchdog extends Thread {
    static final String TAG = "Watchdog";
    static final boolean localLOGV = false || Config.LOGV;

    // Set this to true to use debug default values.
    static final boolean DB = false;

    static final int MONITOR = 2718;
    static final int GLOBAL_PSS = 2719;

    static final int TIME_TO_WAIT = DB ? 15*1000 : 60*1000;
    static final int EVENT_LOG_TAG = 2802;
    static final int EVENT_LOG_PROC_PSS_TAG = 2803;
    static final int EVENT_LOG_SOFT_RESET_TAG = 2804;
    static final int EVENT_LOG_HARD_RESET_TAG = 2805;
    static final int EVENT_LOG_PSS_STATS_TAG = 2806;
    static final int EVENT_LOG_PROC_STATS_TAG = 2807;
    static final int EVENT_LOG_SCHEDULED_REBOOT_TAG = 2808;
    static final int EVENT_LOG_MEMINFO_TAG = 2809;
    static final int EVENT_LOG_VMSTAT_TAG = 2810;
    static final int EVENT_LOG_REQUESTED_REBOOT_TAG = 2811;

    static final int MEMCHECK_DEFAULT_INTERVAL = DB ? 30 : 30*60; // 30 minutes
    static final int MEMCHECK_DEFAULT_LOG_REALTIME_INTERVAL = DB ? 60 : 2*60*60;      // 2 hours
    static final int MEMCHECK_DEFAULT_SYSTEM_SOFT_THRESHOLD = (DB ? 10:16)*1024*1024; // 16MB
    static final int MEMCHECK_DEFAULT_SYSTEM_HARD_THRESHOLD = (DB ? 14:20)*1024*1024; // 20MB
    static final int MEMCHECK_DEFAULT_PHONE_SOFT_THRESHOLD = (DB ? 4:8)*1024*1024;    // 8MB
    static final int MEMCHECK_DEFAULT_PHONE_HARD_THRESHOLD = (DB ? 8:12)*1024*1024;   // 12MB

    static final int MEMCHECK_DEFAULT_EXEC_START_TIME = 1*60*60;           // 1:00am
    static final int MEMCHECK_DEFAULT_EXEC_END_TIME = 5*60*60;             // 5:00am
    static final int MEMCHECK_DEFAULT_MIN_SCREEN_OFF = DB ? 1*60 : 5*60;   // 5 minutes
    static final int MEMCHECK_DEFAULT_MIN_ALARM = DB ? 1*60 : 3*60;        // 3 minutes
    static final int MEMCHECK_DEFAULT_RECHECK_INTERVAL = DB ? 1*60 : 5*60; // 5 minutes

    static final int REBOOT_DEFAULT_INTERVAL = DB ? 1 : 0;                 // never force reboot
    static final int REBOOT_DEFAULT_START_TIME = 3*60*60;                  // 3:00am
    static final int REBOOT_DEFAULT_WINDOW = 60*60;                        // within 1 hour

    static final String CHECKUP_ACTION = "com.android.service.Watchdog.CHECKUP";
    static final String REBOOT_ACTION = "com.android.service.Watchdog.REBOOT";

    static Watchdog sWatchdog;

    /* This handler will be used to post message back onto the main thread */
    final Handler mHandler;
    final Runnable mGlobalPssCollected;
    final ArrayList<Monitor> mMonitors = new ArrayList<Monitor>();
    ContentResolver mResolver;
    BatteryService mBattery;
    PowerManagerService mPower;
    AlarmManagerService mAlarm;
    ActivityManagerService mActivity;
    boolean mCompleted;
    boolean mForceKillSystem;
    Monitor mCurrentMonitor;

    PssRequestor mPhoneReq;
    int mPhonePid;
    int mPhonePss;

    long mLastMemCheckTime = -(MEMCHECK_DEFAULT_INTERVAL*1000);
    boolean mHavePss;
    long mLastMemCheckRealtime = -(MEMCHECK_DEFAULT_LOG_REALTIME_INTERVAL*1000);
    boolean mHaveGlobalPss;
    final MemMonitor mSystemMemMonitor = new MemMonitor("system",
            Settings.Gservices.MEMCHECK_SYSTEM_ENABLED,
            Settings.Gservices.MEMCHECK_SYSTEM_SOFT_THRESHOLD,
            MEMCHECK_DEFAULT_SYSTEM_SOFT_THRESHOLD,
            Settings.Gservices.MEMCHECK_SYSTEM_HARD_THRESHOLD,
            MEMCHECK_DEFAULT_SYSTEM_HARD_THRESHOLD);
    final MemMonitor mPhoneMemMonitor = new MemMonitor("com.android.phone",
            Settings.Gservices.MEMCHECK_PHONE_ENABLED,
            Settings.Gservices.MEMCHECK_PHONE_SOFT_THRESHOLD,
            MEMCHECK_DEFAULT_PHONE_SOFT_THRESHOLD,
            Settings.Gservices.MEMCHECK_PHONE_HARD_THRESHOLD,
            MEMCHECK_DEFAULT_PHONE_HARD_THRESHOLD);

    final Calendar mCalendar = Calendar.getInstance();
    long mMemcheckLastTime;
    long mMemcheckExecStartTime;
    long mMemcheckExecEndTime;
    int mMinScreenOff = MEMCHECK_DEFAULT_MIN_SCREEN_OFF;
    int mMinAlarm = MEMCHECK_DEFAULT_MIN_ALARM;
    boolean mNeedScheduledCheck;
    PendingIntent mCheckupIntent;
    PendingIntent mRebootIntent;

    long mBootTime;
    int mRebootInterval;

    boolean mReqRebootNoWait;     // should wait for one interval before reboot?
    int mReqRebootInterval = -1;  // >= 0 if a reboot has been requested
    int mReqRebootStartTime = -1; // >= 0 if a specific start time has been requested
    int mReqRebootWindow = -1;    // >= 0 if a specific window has been requested
    int mReqMinScreenOff = -1;    // >= 0 if a specific screen off time has been requested
    int mReqMinNextAlarm = -1;    // >= 0 if specific time to next alarm has been requested
    int mReqRecheckInterval= -1;  // >= 0 if a specific recheck interval has been requested

    /**
     * This class monitors the memory in a particular process.
     */
    final class MemMonitor {
        final String mProcessName;
        final String mEnabledSetting;
        final String mSoftSetting;
        final String mHardSetting;

        int mSoftThreshold;
        int mHardThreshold;
        boolean mEnabled;
        long mLastPss;

        static final int STATE_OK = 0;
        static final int STATE_SOFT = 1;
        static final int STATE_HARD = 2;
        int mState;

        MemMonitor(String processName, String enabledSetting,
                String softSetting, int defSoftThreshold,
                String hardSetting, int defHardThreshold) {
            mProcessName = processName;
            mEnabledSetting = enabledSetting;
            mSoftSetting = softSetting;
            mHardSetting = hardSetting;
            mSoftThreshold = defSoftThreshold;
            mHardThreshold = defHardThreshold;
        }

        void retrieveSettings(ContentResolver resolver) {
            mSoftThreshold = Settings.Gservices.getInt(
                    resolver, mSoftSetting, mSoftThreshold);
            mHardThreshold = Settings.Gservices.getInt(
                    resolver, mHardSetting, mHardThreshold);
            mEnabled = Settings.Gservices.getInt(
                    resolver, mEnabledSetting, 0) != 0;
        }

        boolean checkLocked(long curTime, int pid, int pss) {
            mLastPss = pss;
            if (mLastPss < mSoftThreshold) {
                mState = STATE_OK;
            } else if (mLastPss < mHardThreshold) {
                mState = STATE_SOFT;
            } else {
                mState = STATE_HARD;
            }
            EventLog.writeEvent(EVENT_LOG_PROC_PSS_TAG, mProcessName, pid, mLastPss);

            if (mState == STATE_OK) {
                // Memory is good, don't recover.
                return false;
            }

            if (mState == STATE_HARD) {
                // Memory is really bad, kill right now.
                EventLog.writeEvent(EVENT_LOG_HARD_RESET_TAG, mProcessName, pid,
                        mHardThreshold, mLastPss);
                return mEnabled;
            }

            // It is time to schedule a reset...
            // Check if we are currently within the time to kill processes due
            // to memory use.
            computeMemcheckTimesLocked(curTime);
            String skipReason = null;
            if (curTime < mMemcheckExecStartTime || curTime > mMemcheckExecEndTime) {
                skipReason = "time";
            } else {
                skipReason = shouldWeBeBrutalLocked(curTime);
            }
            EventLog.writeEvent(EVENT_LOG_SOFT_RESET_TAG, mProcessName, pid,
                    mSoftThreshold, mLastPss, skipReason != null ? skipReason : "");
            if (skipReason != null) {
                mNeedScheduledCheck = true;
                return false;
            }
            return mEnabled;
        }

        void clear() {
            mLastPss = 0;
            mState = STATE_OK;
        }
    }

    /**
     * Used for scheduling monitor callbacks and checking memory usage.
     */
    final class HeartbeatHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case GLOBAL_PSS: {
                    if (mHaveGlobalPss) {
                        // During the last pass we collected pss information, so
                        // now it is time to report it.
                        mHaveGlobalPss = false;
                        if (localLOGV) Log.v(TAG, "Received global pss, logging.");
                        logGlobalMemory();
                    }
                } break;

                case MONITOR: {
                    if (mHavePss) {
                        // During the last pass we collected pss information, so
                        // now it is time to report it.
                        mHavePss = false;
                        if (localLOGV) Log.v(TAG, "Have pss, checking memory.");
                        checkMemory();
                    }

                    if (mHaveGlobalPss) {
                        // During the last pass we collected pss information, so
                        // now it is time to report it.
                        mHaveGlobalPss = false;
                        if (localLOGV) Log.v(TAG, "Have global pss, logging.");
                        logGlobalMemory();
                    }

                    long now = SystemClock.uptimeMillis();

                    // See if we should force a reboot.
                    int rebootInterval = mReqRebootInterval >= 0
                            ? mReqRebootInterval : Settings.Gservices.getInt(
                            mResolver, Settings.Gservices.REBOOT_INTERVAL,
                            REBOOT_DEFAULT_INTERVAL);
                    if (mRebootInterval != rebootInterval) {
                        mRebootInterval = rebootInterval;
                        // We have been running long enough that a reboot can
                        // be considered...
                        checkReboot(false);
                    }

                    // See if we should check memory conditions.
                    long memCheckInterval = Settings.Gservices.getLong(
                            mResolver, Settings.Gservices.MEMCHECK_INTERVAL,
                            MEMCHECK_DEFAULT_INTERVAL) * 1000;
                    if ((mLastMemCheckTime+memCheckInterval) < now) {
                        // It is now time to collect pss information.  This
                        // is async so we won't report it now.  And to keep
                        // things simple, we will assume that everyone has
                        // reported back by the next MONITOR message.
                        mLastMemCheckTime = now;
                        if (localLOGV) Log.v(TAG, "Collecting memory usage.");
                        collectMemory();
                        mHavePss = true;

                        long memCheckRealtimeInterval = Settings.Gservices.getLong(
                                mResolver, Settings.Gservices.MEMCHECK_LOG_REALTIME_INTERVAL,
                                MEMCHECK_DEFAULT_LOG_REALTIME_INTERVAL) * 1000;
                        long realtimeNow = SystemClock.elapsedRealtime();
                        if ((mLastMemCheckRealtime+memCheckRealtimeInterval) < realtimeNow) {
                            mLastMemCheckRealtime = realtimeNow;
                            if (localLOGV) Log.v(TAG, "Collecting global memory usage.");
                            collectGlobalMemory();
                            mHaveGlobalPss = true;
                        }
                    }

                    final int size = mMonitors.size();
                    for (int i = 0 ; i < size ; i++) {
                        mCurrentMonitor = mMonitors.get(i);
                        mCurrentMonitor.monitor();
                    }

                    synchronized (Watchdog.this) {
                        mCompleted = true;
                        mCurrentMonitor = null;
                    }
                } break;
            }
        }
    }

    final class GlobalPssCollected implements Runnable {
        public void run() {
            mHandler.sendEmptyMessage(GLOBAL_PSS);
        }
    }

    final class CheckupReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context c, Intent intent) {
            if (localLOGV) Log.v(TAG, "Alarm went off, checking memory.");
            checkMemory();
        }
    }

    final class RebootReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context c, Intent intent) {
            if (localLOGV) Log.v(TAG, "Alarm went off, checking reboot.");
            checkReboot(true);
        }
    }

    final class RebootRequestReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context c, Intent intent) {
            mReqRebootNoWait = intent.getIntExtra("nowait", 0) != 0;
            mReqRebootInterval = intent.getIntExtra("interval", -1);
            mReqRebootStartTime = intent.getIntExtra("startTime", -1);
            mReqRebootWindow = intent.getIntExtra("window", -1);
            mReqMinScreenOff = intent.getIntExtra("minScreenOff", -1);
            mReqMinNextAlarm = intent.getIntExtra("minNextAlarm", -1);
            mReqRecheckInterval = intent.getIntExtra("recheckInterval", -1);
            EventLog.writeEvent(EVENT_LOG_REQUESTED_REBOOT_TAG,
                    mReqRebootNoWait ? 1 : 0, mReqRebootInterval,
                            mReqRecheckInterval, mReqRebootStartTime,
                    mReqRebootWindow, mReqMinScreenOff, mReqMinNextAlarm);
            checkReboot(true);
        }
    }

    public interface Monitor {
        void monitor();
    }

    public interface PssRequestor {
        void requestPss();
    }

    public class PssStats {
        public int mEmptyPss;
        public int mEmptyCount;
        public int mBackgroundPss;
        public int mBackgroundCount;
        public int mServicePss;
        public int mServiceCount;
        public int mVisiblePss;
        public int mVisibleCount;
        public int mForegroundPss;
        public int mForegroundCount;

        public int mNoPssCount;

        public int mProcDeaths[] = new int[10];
    }

    public static Watchdog getInstance() {
        if (sWatchdog == null) {
            sWatchdog = new Watchdog();
        }

        return sWatchdog;
    }

    private Watchdog() {
        super("watchdog");
        mHandler = new HeartbeatHandler();
        mGlobalPssCollected = new GlobalPssCollected();
    }

    public void init(Context context, BatteryService battery,
            PowerManagerService power, AlarmManagerService alarm,
            ActivityManagerService activity) {
        mResolver = context.getContentResolver();
        mBattery = battery;
        mPower = power;
        mAlarm = alarm;
        mActivity = activity;

        context.registerReceiver(new CheckupReceiver(),
                new IntentFilter(CHECKUP_ACTION));
        mCheckupIntent = PendingIntent.getBroadcast(context,
                0, new Intent(CHECKUP_ACTION), 0);

        context.registerReceiver(new RebootReceiver(),
                new IntentFilter(REBOOT_ACTION));
        mRebootIntent = PendingIntent.getBroadcast(context,
                0, new Intent(REBOOT_ACTION), 0);

        context.registerReceiver(new RebootRequestReceiver(),
                new IntentFilter(Intent.ACTION_REBOOT),
                android.Manifest.permission.REBOOT, null);

        mBootTime = System.currentTimeMillis();
    }

    public void processStarted(PssRequestor req, String name, int pid) {
        synchronized (this) {
            if ("com.android.phone".equals(name)) {
                mPhoneReq = req;
                mPhonePid = pid;
                mPhonePss = 0;
            }
        }
    }

    public void reportPss(PssRequestor req, String name, int pss) {
        synchronized (this) {
            if (mPhoneReq == req) {
                mPhonePss = pss;
            }
        }
    }

    public void addMonitor(Monitor monitor) {
        synchronized (this) {
            if (isAlive()) {
                throw new RuntimeException("Monitors can't be added while the Watchdog is running");
            }
            mMonitors.add(monitor);
        }
    }

    /**
     * Retrieve memory usage information from specific processes being
     * monitored.  This is an async operation, so must be done before doing
     * memory checks.
     */
    void collectMemory() {
        synchronized (this) {
            if (mPhoneReq != null) {
                mPhoneReq.requestPss();
            }
        }
    }

    /**
     * Retrieve memory usage over all application processes.  This is an
     * async operation, so must be done before doing memory checks.
     */
    void collectGlobalMemory() {
        mActivity.requestPss(mGlobalPssCollected);
    }

    /**
     * Check memory usage in the system, scheduling kills/reboots as needed.
     * This always runs on the mHandler thread.
     */
    void checkMemory() {
        boolean needScheduledCheck;
        long curTime;
        long nextTime = 0;

        long recheckInterval = Settings.Gservices.getLong(
                mResolver, Settings.Gservices.MEMCHECK_RECHECK_INTERVAL,
                MEMCHECK_DEFAULT_RECHECK_INTERVAL) * 1000;

        mSystemMemMonitor.retrieveSettings(mResolver);
        mPhoneMemMonitor.retrieveSettings(mResolver);
        retrieveBrutalityAmount();

        synchronized (this) {
            curTime = System.currentTimeMillis();
            mNeedScheduledCheck = false;

            // How is the system doing?
            if (mSystemMemMonitor.checkLocked(curTime, Process.myPid(),
                    (int)Process.getPss(Process.myPid()))) {
                // Not good!  Time to suicide.
                mForceKillSystem = true;
                notifyAll();
                return;
            }

            // How is the phone process doing?
            if (mPhoneReq != null) {
                if (mPhoneMemMonitor.checkLocked(curTime, mPhonePid,
                        mPhonePss)) {
                    // Just kill the phone process and let it restart.
                    Process.killProcess(mPhonePid);
                }
            } else {
                mPhoneMemMonitor.clear();
            }

            needScheduledCheck = mNeedScheduledCheck;
            if (needScheduledCheck) {
                // Something is going bad, but now is not a good time to
                // tear things down...  schedule an alarm to check again soon.
                nextTime = curTime + recheckInterval;
                if (nextTime < mMemcheckExecStartTime) {
                    nextTime = mMemcheckExecStartTime;
                } else if (nextTime >= mMemcheckExecEndTime){
                    // Need to check during next exec time...  so that needs
                    // to be computed.
                    if (localLOGV) Log.v(TAG, "Computing next time range");
                    computeMemcheckTimesLocked(nextTime);
                    nextTime = mMemcheckExecStartTime;
                }

                if (localLOGV) {
                    mCalendar.setTimeInMillis(nextTime);
                    Log.v(TAG, "Next Alarm Time: " + mCalendar);
                }
            }
        }

        if (needScheduledCheck) {
            if (localLOGV) Log.v(TAG, "Scheduling next memcheck alarm for "
                    + ((nextTime-curTime)/1000/60) + "m from now");
            mAlarm.remove(mCheckupIntent);
            mAlarm.set(AlarmManager.RTC_WAKEUP, nextTime, mCheckupIntent);
        } else {
            if (localLOGV) Log.v(TAG, "No need to schedule a memcheck alarm!");
            mAlarm.remove(mCheckupIntent);
        }
    }

    final PssStats mPssStats = new PssStats();
    final String[] mMemInfoFields = new String[] {
            "MemFree:", "Buffers:", "Cached:",
            "Active:", "Inactive:",
            "AnonPages:", "Mapped:", "Slab:",
            "SReclaimable:", "SUnreclaim:", "PageTables:" };
    final long[] mMemInfoSizes = new long[mMemInfoFields.length];
    final String[] mVMStatFields = new String[] {
            "pgfree ", "pgactivate ", "pgdeactivate ",
            "pgfault ", "pgmajfault " };
    final long[] mVMStatSizes = new long[mVMStatFields.length];
    final long[] mPrevVMStatSizes = new long[mVMStatFields.length];
    long mLastLogGlobalMemoryTime;

    void logGlobalMemory() {
        PssStats stats = mPssStats;
        mActivity.collectPss(stats);
        EventLog.writeEvent(EVENT_LOG_PSS_STATS_TAG,
                stats.mEmptyPss, stats.mEmptyCount,
                stats.mBackgroundPss, stats.mBackgroundCount,
                stats.mServicePss, stats.mServiceCount,
                stats.mVisiblePss, stats.mVisibleCount,
                stats.mForegroundPss, stats.mForegroundCount,
                stats.mNoPssCount);
        EventLog.writeEvent(EVENT_LOG_PROC_STATS_TAG,
                stats.mProcDeaths[0], stats.mProcDeaths[1], stats.mProcDeaths[2],
                stats.mProcDeaths[3], stats.mProcDeaths[4]);
        Process.readProcLines("/proc/meminfo", mMemInfoFields, mMemInfoSizes);
        for (int i=0; i<mMemInfoSizes.length; i++) {
            mMemInfoSizes[i] *= 1024;
        }
        EventLog.writeEvent(EVENT_LOG_MEMINFO_TAG,
                (int)mMemInfoSizes[0], (int)mMemInfoSizes[1], (int)mMemInfoSizes[2],
                (int)mMemInfoSizes[3], (int)mMemInfoSizes[4],
                (int)mMemInfoSizes[5], (int)mMemInfoSizes[6], (int)mMemInfoSizes[7],
                (int)mMemInfoSizes[8], (int)mMemInfoSizes[9], (int)mMemInfoSizes[10]);
        long now = SystemClock.uptimeMillis();
        long dur = now - mLastLogGlobalMemoryTime;
        mLastLogGlobalMemoryTime = now;
        Process.readProcLines("/proc/vmstat", mVMStatFields, mVMStatSizes);
        for (int i=0; i<mVMStatSizes.length; i++) {
            long v = mVMStatSizes[i];
            mVMStatSizes[i] -= mPrevVMStatSizes[i];
            mPrevVMStatSizes[i] = v;
        }
        EventLog.writeEvent(EVENT_LOG_VMSTAT_TAG, dur,
                (int)mVMStatSizes[0], (int)mVMStatSizes[1], (int)mVMStatSizes[2],
                (int)mVMStatSizes[3], (int)mVMStatSizes[4]);
    }

    void checkReboot(boolean fromAlarm) {
        int rebootInterval = mReqRebootInterval >= 0 ? mReqRebootInterval
                : Settings.Gservices.getInt(
                mResolver, Settings.Gservices.REBOOT_INTERVAL,
                REBOOT_DEFAULT_INTERVAL);
        mRebootInterval = rebootInterval;
        if (rebootInterval <= 0) {
            // No reboot interval requested.
            if (localLOGV) Log.v(TAG, "No need to schedule a reboot alarm!");
            mAlarm.remove(mRebootIntent);
            return;
        }

        long rebootStartTime = mReqRebootStartTime >= 0 ? mReqRebootStartTime
                : Settings.Gservices.getLong(
                mResolver, Settings.Gservices.REBOOT_START_TIME,
                REBOOT_DEFAULT_START_TIME);
        long rebootWindowMillis = (mReqRebootWindow >= 0 ? mReqRebootWindow
                : Settings.Gservices.getLong(
                mResolver, Settings.Gservices.REBOOT_WINDOW,
                REBOOT_DEFAULT_WINDOW)) * 1000;
        long recheckInterval = (mReqRecheckInterval >= 0 ? mReqRecheckInterval
                : Settings.Gservices.getLong(
                mResolver, Settings.Gservices.MEMCHECK_RECHECK_INTERVAL,
                MEMCHECK_DEFAULT_RECHECK_INTERVAL)) * 1000;

        retrieveBrutalityAmount();

        long realStartTime;
        long now;

        synchronized (this) {
            now = System.currentTimeMillis();
            realStartTime = computeCalendarTime(mCalendar, now,
                    rebootStartTime);

            long rebootIntervalMillis = rebootInterval*24*60*60*1000;
            if (DB || mReqRebootNoWait ||
                    (now-mBootTime) >= (rebootIntervalMillis-rebootWindowMillis)) {
                if (fromAlarm && rebootWindowMillis <= 0) {
                    // No reboot window -- just immediately reboot.
                    EventLog.writeEvent(EVENT_LOG_SCHEDULED_REBOOT_TAG, now,
                            (int)rebootIntervalMillis, (int)rebootStartTime*1000,
                            (int)rebootWindowMillis, "");
                    rebootSystem("Checkin scheduled forced");
                    return;
                }

                // Are we within the reboot window?
                if (now < realStartTime) {
                    // Schedule alarm for next check interval.
                    realStartTime = computeCalendarTime(mCalendar,
                            now, rebootStartTime);
                } else if (now < (realStartTime+rebootWindowMillis)) {
                    String doit = shouldWeBeBrutalLocked(now);
                    EventLog.writeEvent(EVENT_LOG_SCHEDULED_REBOOT_TAG, now,
                            (int)rebootInterval, (int)rebootStartTime*1000,
                            (int)rebootWindowMillis, doit != null ? doit : "");
                    if (doit == null) {
                        rebootSystem("Checked scheduled range");
                        return;
                    }

                    // Schedule next alarm either within the window or in the
                    // next interval.
                    if ((now+recheckInterval) >= (realStartTime+rebootWindowMillis)) {
                        realStartTime = computeCalendarTime(mCalendar,
                                now + rebootIntervalMillis, rebootStartTime);
                    } else {
                        realStartTime = now + recheckInterval;
                    }
                } else {
                    // Schedule alarm for next check interval.
                    realStartTime = computeCalendarTime(mCalendar,
                            now + rebootIntervalMillis, rebootStartTime);
                }
            }
        }

        if (localLOGV) Log.v(TAG, "Scheduling next reboot alarm for "
                + ((realStartTime-now)/1000/60) + "m from now");
        mAlarm.remove(mRebootIntent);
        mAlarm.set(AlarmManager.RTC_WAKEUP, realStartTime, mRebootIntent);
    }

    /**
     * Perform a full reboot of the system.
     */
    void rebootSystem(String reason) {
        Log.i(TAG, "Rebooting system because: " + reason);
        android.os.Power.reboot(reason);
    }

    /**
     * Load the current Gservices settings for when
     * {@link #shouldWeBeBrutalLocked} will allow the brutality to happen.
     * Must not be called with the lock held.
     */
    void retrieveBrutalityAmount() {
        mMinScreenOff = (mReqMinScreenOff >= 0 ? mReqMinScreenOff
                : Settings.Gservices.getInt(
                mResolver, Settings.Gservices.MEMCHECK_MIN_SCREEN_OFF,
                MEMCHECK_DEFAULT_MIN_SCREEN_OFF)) * 1000;
        mMinAlarm = (mReqMinNextAlarm >= 0 ? mReqMinNextAlarm
                : Settings.Gservices.getInt(
                mResolver, Settings.Gservices.MEMCHECK_MIN_ALARM,
                MEMCHECK_DEFAULT_MIN_ALARM)) * 1000;
    }

    /**
     * Determine whether it is a good time to kill, crash, or otherwise
     * plunder the current situation for the overall long-term benefit of
     * the world.
     *
     * @param curTime The current system time.
     * @return Returns null if this is a good time, else a String with the
     * text of why it is not a good time.
     */
    String shouldWeBeBrutalLocked(long curTime) {
        if (mBattery == null || !mBattery.isPowered()) {
            return "battery";
        }

        if (mMinScreenOff >= 0 && (mPower == null ||
                mPower.timeSinceScreenOn() < mMinScreenOff)) {
            return "screen";
        }

        if (mMinAlarm >= 0 && (mAlarm == null ||
                mAlarm.timeToNextAlarm() < mMinAlarm)) {
            return "alarm";
        }

        return null;
    }

    /**
     * Compute the times during which we next would like to perform process
     * restarts.
     *
     * @param curTime The current system time.
     */
    void computeMemcheckTimesLocked(long curTime) {
        if (mMemcheckLastTime == curTime) {
            return;
        }

        mMemcheckLastTime = curTime;

        long memcheckExecStartTime = Settings.Gservices.getLong(
                mResolver, Settings.Gservices.MEMCHECK_EXEC_START_TIME,
                MEMCHECK_DEFAULT_EXEC_START_TIME);
        long memcheckExecEndTime = Settings.Gservices.getLong(
                mResolver, Settings.Gservices.MEMCHECK_EXEC_END_TIME,
                MEMCHECK_DEFAULT_EXEC_END_TIME);

        mMemcheckExecEndTime = computeCalendarTime(mCalendar, curTime,
                memcheckExecEndTime);
        if (mMemcheckExecEndTime < curTime) {
            memcheckExecStartTime += 24*60*60;
            memcheckExecEndTime += 24*60*60;
            mMemcheckExecEndTime = computeCalendarTime(mCalendar, curTime,
                    memcheckExecEndTime);
        }
        mMemcheckExecStartTime = computeCalendarTime(mCalendar, curTime,
                memcheckExecStartTime);

        if (localLOGV) {
            mCalendar.setTimeInMillis(curTime);
            Log.v(TAG, "Current Time: " + mCalendar);
            mCalendar.setTimeInMillis(mMemcheckExecStartTime);
            Log.v(TAG, "Start Check Time: " + mCalendar);
            mCalendar.setTimeInMillis(mMemcheckExecEndTime);
            Log.v(TAG, "End Check Time: " + mCalendar);
        }
    }

    static long computeCalendarTime(Calendar c, long curTime,
            long secondsSinceMidnight) {

        // start with now
        c.setTimeInMillis(curTime);

        int val = (int)secondsSinceMidnight / (60*60);
        c.set(Calendar.HOUR_OF_DAY, val);
        secondsSinceMidnight -= val * (60*60);
        val = (int)secondsSinceMidnight / 60;
        c.set(Calendar.MINUTE, val);
        c.set(Calendar.SECOND, (int)secondsSinceMidnight - (val*60));
        c.set(Calendar.MILLISECOND, 0);

        long newTime = c.getTimeInMillis();
        if (newTime < curTime) {
            // The given time (in seconds since midnight) has already passed for today, so advance
            // by one day (due to daylight savings, etc., the delta may differ from 24 hours).
            c.add(Calendar.DAY_OF_MONTH, 1);
            newTime = c.getTimeInMillis();
        }

        return newTime;
    }

    @Override
    public void run() {
        while (true) {
            mCompleted = false;
            mHandler.sendEmptyMessage(MONITOR);

            synchronized (this) {
                long timeout = TIME_TO_WAIT;

                // NOTE: We use uptimeMillis() here because we do not want to increment the time we
                // wait while asleep. If the device is asleep then the thing that we are waiting
                // to timeout on is asleep as well and won't have a chance to run. Causing a false
                // positive on when to kill things.
                long start = SystemClock.uptimeMillis();
                do {
                    try {
                        wait(timeout);
                    } catch (InterruptedException e) {
                        if (SystemProperties.getBoolean("ro.secure", false)) {
                            // If this is a secure build, just log the error.
                            Log.e("WatchDog", "Woof! Woof! Interrupter!");
                        } else {
                            throw new AssertionError("Someone interrupted the watchdog");
                        }
                    }
                    timeout = TIME_TO_WAIT - (SystemClock.uptimeMillis() - start);
                } while (timeout > 0 && !mForceKillSystem);

                if (mCompleted && !mForceKillSystem) {
                    // The monitors have returned.
                    continue;
                }
            }

            // If we got here, that means that the system is most likely hung.
            // First send a SIGQUIT so that we can see where it was hung. Then
            // kill this process so that the system will restart.
            String name = (mCurrentMonitor != null) ? mCurrentMonitor.getClass().getName() : "null";
            EventLog.writeEvent(EVENT_LOG_TAG, name);
            Process.sendSignal(Process.myPid(), Process.SIGNAL_QUIT);

            // Wait a bit longer before killing so we can make sure that the stacks are captured.
            try {
                Thread.sleep(10*1000);
            } catch (InterruptedException e) {
            }

            // Only kill the process if the debugger is not attached.
            if (!Debug.isDebuggerConnected()) {
                Process.killProcess(Process.myPid());
            }
        }
    }
}