Android系统层Watchdog机制源码分析

public final class HandlerChecker implements Runnable {88        private final Handler mHandler;89        private final String mName;90        private final long mWaitMax;91        private final ArrayList<Monitor> mMonitors = new ArrayList<Monitor>();92        private boolean mCompleted;93        private Monitor mCurrentMonitor;94        private long mStartTime;9596        HandlerChecker(Handler handler, String name, long waitMaxMillis) {97            mHandler = handler;98            mName = name;99            mWaitMax = waitMaxMillis;100            mCompleted = true;101        }102103        public void addMonitor(Monitor monitor) {104            mMonitors.add(monitor);105        }106        // 记录当前的开始时间107        public void scheduleCheckLocked() {108            if (mMonitors.size() == 0 && mHandler.getLooper().getQueue().isPolling()) {109                // If the target looper has recently been polling, then110                // there is no reason to enqueue our checker on it since that111                // is as good as it not being deadlocked.  This avoid having112                // to do a context switch to check the thread.  Note that we113                // only do this if mCheckReboot is false and we have no114                // monitors, since those would need to be executed at this point.115                mCompleted = true;116                return;117            }118119            if (!mCompleted) {120                // we already have a check in flight, so no need121                return;122            }123124            mCompleted = false;125            mCurrentMonitor = null;126            mStartTime = SystemClock.uptimeMillis();127            mHandler.postAtFrontOfQueue(this);128        }129130        public boolean isOverdueLocked() {131            return (!mCompleted) && (SystemClock.uptimeMillis() > mStartTime + mWaitMax);132        }133        // 获取完成时间标识134        public int getCompletionStateLocked() {135            if (mCompleted) {136                return COMPLETED;137            } else {138                long latency = SystemClock.uptimeMillis() - mStartTime;139                if (latency < mWaitMax/2) {140                    return WAITING;141                } else if (latency < mWaitMax) {142                    return WAITED_HALF;143                }144            }145            return OVERDUE;146        }147148        public Thread getThread() {149            return mHandler.getLooper().getThread();150        }151152        public String getName() {153            return mName;154        }155156        public String describeBlockedStateLocked() {157            if (mCurrentMonitor == null) {158                return "Blocked in handler on " + mName + " (" + getThread().getName() + ")";159            } else {160                return "Blocked in monitor " + mCurrentMonitor.getClass().getName()161                        + " on " + mName + " (" + getThread().getName() + ")";162            }163        }164165        @Override166        public void run() {167            final int size = mMonitors.size();168            for (int i = 0 ; i < size ; i++) {169                synchronized (Watchdog.this) {170                    mCurrentMonitor = mMonitors.get(i);171                }172                mCurrentMonitor.monitor();173            }174175            synchronized (Watchdog.this) {176                mCompleted = true;177                mCurrentMonitor = null;178            }179        }180    }