appNotResponding的代码处理流程

1. 可能导致 anr的情景：activity, service, provice, broadcast都可能产生anr
具体产生的策略这里没有关注，这里只关注发生 anr后的代码流程，也就是关注appNotResponding函数
    /**
     * Handle input dispatching timeouts.
     * Returns whether input dispatching should be aborted or not.
     */
inputDispatch:
    public boolean inputDispatchingTimedOut(final ProcessRecord proc,
            final ActivityRecord activity, final ActivityRecord parent,
            final boolean aboveSystem, String reason) {
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    appNotResponding(proc, activity, parent, aboveSystem, annotation);
                }
            });
    }


Provider:
    public void appNotRespondingViaProvider(IBinder connection) {
        enforceCallingPermission(
                android.Manifest.permission.REMOVE_TASKS, "appNotRespondingViaProvider()");


        final ContentProviderConnection conn = (ContentProviderConnection) connection;
        if (conn == null) {
            Slog.w(TAG, "ContentProviderConnection is null");
            return;
        }


        final ProcessRecord host = conn.provider.proc;
        if (host == null) {
            Slog.w(TAG, "Failed to find hosting ProcessRecord");
            return;
        }


        final long token = Binder.clearCallingIdentity();
        try {
            appNotResponding(host, null, null, false, "ContentProvider not responding");
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }


service:
    void serviceTimeout(ProcessRecord proc) {
        String anrMessage = null;


        synchronized(mAm) {
            if (proc.executingServices.size() == 0 || proc.thread == null) {
                return;
            }
            if (timeout != null && mAm.mLruProcesses.contains(proc)) {
                Slog.w(TAG, "Timeout executing service: " + timeout);
                StringWriter sw = new StringWriter();
                PrintWriter pw = new FastPrintWriter(sw, false, 1024);
                pw.println(timeout);
                timeout.dump(pw, "    ");
                pw.close();
                mLastAnrDump = sw.toString();
                mAm.mHandler.removeCallbacks(mLastAnrDumpClearer);
                mAm.mHandler.postDelayed(mLastAnrDumpClearer, LAST_ANR_LIFETIME_DURATION_MSECS);
                anrMessage = "executing service " + timeout.shortName;
            } else {
                Message msg = mAm.mHandler.obtainMessage(
                        ActivityManagerService.SERVICE_TIMEOUT_MSG);
                msg.obj = proc;
                mAm.mHandler.sendMessageAtTime(msg, proc.execServicesFg
                        ? (nextTime+SERVICE_TIMEOUT) : (nextTime + SERVICE_BACKGROUND_TIMEOUT));
            }
        }


        if (anrMessage != null) {
            mAm.appNotResponding(proc, null, null, false, anrMessage);
        }
    }


Broadcast:
    final void broadcastTimeoutLocked(boolean fromMsg) {
mHandler.post(new AppNotResponding(app, anrMessage));
    }
/************************************************************************************/


2. appNotResponding代码流程：
    final void appNotResponding(ProcessRecord app, ActivityRecord activity,
            ActivityRecord parent, boolean aboveSystem, final String annotation) {


        ArrayList<Integer> firstPids = new ArrayList<Integer>(5);
        SparseArray<Boolean> lastPids = new SparseArray<Boolean>(20);


        long anrTime = SystemClock.uptimeMillis();
        if (MONITOR_CPU_USAGE) {
            updateCpuStatsNow();
        }


            // In case we come through here for the same app before completing
            // this one, mark as anring now so we will bail out.
            app.notResponding = true;


            // Log the ANR to the event log.
            EventLog.writeEvent(EventLogTags.AM_ANR, app.userId, app.pid,
                    app.processName, app.info.flags, annotation);


            // Dump thread traces as quickly as we can, starting with "interesting" processes.
            firstPids.add(app.pid);


        // Log the ANR to the main log.
        StringBuilder info = new StringBuilder();
        info.setLength(0);
        info.append("ANR in ").append(app.processName);
        if (activity != null && activity.shortComponentName != null) {
            info.append(" (").append(activity.shortComponentName).append(")");
        }
        info.append("\n");
        info.append("PID: ").append(app.pid).append("\n");
        if (annotation != null) {
            info.append("Reason: ").append(annotation).append("\n");
        }
        if (parent != null && parent != activity) {
            info.append("Parent: ").append(parent.shortComponentName).append("\n");
        }
        String cpuInfo = null;
        if (MONITOR_CPU_USAGE) {
            updateCpuStatsNow();
            synchronized (mProcessCpuTracker) {
                cpuInfo = mProcessCpuTracker.printCurrentState(anrTime);
            }
            info.append(processCpuTracker.printCurrentLoad());
            info.append(cpuInfo);
        }


        info.append(processCpuTracker.printCurrentState(anrTime));


        Slog.e(TAG, info.toString());




        File tracesFile = dumpStackTraces(true, firstPids, processCpuTracker, lastPids,
                NATIVE_STACKS_OF_INTEREST);
        addErrorToDropBox("anr", app, app.processName, activity, parent, annotation,
                cpuInfo, tracesFile, null);




            //Set the trace file name to app name + current date format to avoid overrinding trace file
            String tracesPath = SystemProperties.get("dalvik.vm.stack-trace-file", null);
            if (tracesPath != null && tracesPath.length() != 0) {
                File traceRenameFile = new File(tracesPath);
                String newTracesPath;
                int lpos = tracesPath.lastIndexOf (".");
                if (-1 != lpos)
                    newTracesPath = tracesPath.substring (0, lpos) + "_" + app.processName + "_" + mTraceDateFormat.format(new Date()) + tracesPath.substring (lpos);
                else
                    newTracesPath = tracesPath + "_" + app.processName;


                traceRenameFile.renameTo(new File(newTracesPath));
            }


            // Bring up the infamous App Not Responding dialog
            Message msg = Message.obtain();
            HashMap<String, Object> map = new HashMap<String, Object>();
            msg.what = SHOW_NOT_RESPONDING_MSG;
            msg.obj = map;
            msg.arg1 = aboveSystem ? 1 : 0;
            map.put("app", app);
            if (activity != null) {
                map.put("activity", activity);
            }


            mUiHandler.sendMessage(msg);
}


3. ANR是logcat输出：
1398  1445 E ActivityManager: ANR in com.example.ritter.fcandanr (com.example.ritter.fcandanr/.MainActivity)
1398  1445 E ActivityManager: PID: 5639
1398  1445 E ActivityManager: Reason: Input dispatching timed out (Waiting because the touched window's input channel is full.  Outbound queue length: 1.  Wait queue length: 52.)
1398  1445 E ActivityManager: Load: 5.79 / 5.61 / 5.5
1398  1445 E ActivityManager: CPU usage from 30465ms to 0ms ago:
1398  1445 E ActivityManager:   13% 1398/system_server: 5.9% user + 7.2% kernel / faults: 1567 minor 3 major
1398  1445 E ActivityManager:   2% 603/sensors.qcom: 0.6% user + 1.3% kernel / faults: 6 minor
1398  1445 E ActivityManager:   1.4% 5938/kworker/u8:8: 0% user + 1.4% kernel


logcat -b events输出：
am_anr  : [0,5639,com.example.ritter.fcandanr,948485702,Input dispatching timed out (Waiting because the touched window's input channel is full.  Outbound queue length: 1.  Wait queue length: 52.)]


4. dumpStackTraces
4.1 创建文件和文件夹
    /**
     * If a stack trace dump file is configured, dump process stack traces.
     * @param clearTraces causes the dump file to be erased prior to the new
     *    traces being written, if true; when false, the new traces will be
     *    appended to any existing file content.
     * @param firstPids of dalvik VM processes to dump stack traces for first
     * @param lastPids of dalvik VM processes to dump stack traces for last
     * @param nativeProcs optional list of native process names to dump stack crawls
     * @return file containing stack traces, or null if no dump file is configured
     */
    public static File dumpStackTraces(boolean clearTraces, ArrayList<Integer> firstPids,
            ProcessCpuTracker processCpuTracker, SparseArray<Boolean> lastPids, String[] nativeProcs) {
        String tracesPath = SystemProperties.get("dalvik.vm.stack-trace-file", null);
        if (tracesPath == null || tracesPath.length() == 0) {
            return null;
        }


        File tracesFile = new File(tracesPath);
        try {
            File tracesDir = tracesFile.getParentFile();
            if (!tracesDir.exists()) {
                tracesDir.mkdirs();
                if (!SELinux.restorecon(tracesDir)) {
                    return null;
                }
            }
            FileUtils.setPermissions(tracesDir.getPath(), 0775, -1, -1);  // drwxrwxr-x


            if (clearTraces && tracesFile.exists()) tracesFile.delete();
            tracesFile.createNewFile();
            FileUtils.setPermissions(tracesFile.getPath(), 0666, -1, -1); // -rw-rw-rw-
        } catch (IOException e) {
            Slog.w(TAG, "Unable to prepare ANR traces file: " + tracesPath, e);
            return null;
        }


        dumpStackTraces(tracesPath, firstPids, processCpuTracker, lastPids, nativeProcs);
        return tracesFile;
    }




4.2: Process.sendSignal(firstPids.get(i), Process.SIGNAL_QUIT) and observer.wait(200)
    private static void dumpStackTraces(String tracesPath, ArrayList<Integer> firstPids,
            ProcessCpuTracker processCpuTracker, SparseArray<Boolean> lastPids, String[] nativeProcs) {
        // Use a FileObserver to detect when traces finish writing.
        // The order of traces is considered important to maintain for legibility.
        FileObserver observer = new FileObserver(tracesPath, FileObserver.CLOSE_WRITE) {
            @Override
            public synchronized void onEvent(int event, String path) { notify(); }
        };


        try {
            observer.startWatching();


            // First collect all of the stacks of the most important pids.
            if (firstPids != null) {
                try {
                    int num = firstPids.size();
                    for (int i = 0; i < num; i++) {
                        synchronized (observer) {
                            Process.sendSignal(firstPids.get(i), Process.SIGNAL_QUIT);
                            observer.wait(200);  // Wait for write-close, give up after 200msec
                        }
                    }
                } catch (InterruptedException e) {
                    Slog.wtf(TAG, e);
                }
            }


            // Next collect the stacks of the native pids
            if (nativeProcs != null) {
                int[] pids = Process.getPidsForCommands(nativeProcs);
                if (pids != null) {
                    for (int pid : pids) {
                        Debug.dumpNativeBacktraceToFile(pid, tracesPath);
                    }
                }
            }


            // Lastly, measure CPU usage.
            if (processCpuTracker != null) {
                processCpuTracker.init();
                System.gc();
                processCpuTracker.update();
                try {
                    synchronized (processCpuTracker) {
                        processCpuTracker.wait(500); // measure over 1/2 second.
                    }
                } catch (InterruptedException e) {
                }
                processCpuTracker.update();


                // We'll take the stack crawls of just the top apps using CPU.
                final int N = processCpuTracker.countWorkingStats();
                int numProcs = 0;
                for (int i=0; i<N && numProcs<5; i++) {
                    ProcessCpuTracker.Stats stats = processCpuTracker.getWorkingStats(i);
                    if (lastPids.indexOfKey(stats.pid) >= 0) {
                        numProcs++;
                        try {
                            synchronized (observer) {
                                Process.sendSignal(stats.pid, Process.SIGNAL_QUIT);
                                observer.wait(200);  // Wait for write-close, give up after 200msec
                            }
                        } catch (InterruptedException e) {
                            Slog.wtf(TAG, e);
                        }


                    }
                }
            }
        } finally {
            observer.stopWatching();
        }
    }




5. addErrorToDropBox("anr", app, app.processName, activity, parent, annotation,
                cpuInfo, tracesFile, null);
是怎样编程压缩文件的？
// First, accumulate up to one block worth of data in memory before
// deciding whether to compress the data or not.


[e-mail]
    /**
     * Stores human-readable text.  The data may be discarded eventually (or even
     * immediately) if space is limited, or ignored entirely if the tag has been
     * blocked (see {@link #isTagEnabled}).
     *
     * @param tag describing the type of entry being stored
     * @param data value to store
     */
    public void addText(String tag, String data) {
        try { mService.add(new Entry(tag, 0, data)); } catch (RemoteException e) {}
    }


        /** Create a new Entry with plain text contents. */
        public Entry(String tag, long millis, String text) {
            if (tag == null) throw new NullPointerException("tag == null");
            if (text == null) throw new NullPointerException("text == null");


            mTag = tag;
            mTimeMillis = millis;
            mData = text.getBytes();
            mFileDescriptor = null;
            mFlags = IS_TEXT;
        }


        /** @return the uncompressed contents of the entry, or null if the contents were lost */
        public InputStream getInputStream() throws IOException {
            InputStream is;
            if (mData != null) {
                is = new ByteArrayInputStream(mData);
            } else if (mFileDescriptor != null) {
                is = new ParcelFileDescriptor.AutoCloseInputStream(mFileDescriptor);
            } else {
                return null;
            }
            return (mFlags & IS_GZIPPED) != 0 ? new GZIPInputStream(is) : is;
        }


    public void add(DropBoxManager.Entry entry) {
        File temp = null;
        OutputStream output = null;
        final String tag = entry.getTag();
        try {
            int flags = entry.getFlags();
            if ((flags & DropBoxManager.IS_EMPTY) != 0) throw new IllegalArgumentException();


            init();
            if (!isTagEnabled(tag)) return;
            long max = trimToFit();
            long lastTrim = System.currentTimeMillis();


            byte[] buffer = new byte[mBlockSize];
            InputStream input = entry.getInputStream();


            // First, accumulate up to one block worth of data in memory before
            // deciding whether to compress the data or not.


            int read = 0;
            while (read < buffer.length) {
                int n = input.read(buffer, read, buffer.length - read);
                if (n <= 0) break;
                read += n;
            }


            // If we have at least one block, compress it -- otherwise, just write
            // the data in uncompressed form.


            temp = new File(mDropBoxDir, "drop" + Thread.currentThread().getId() + ".tmp");
            int bufferSize = mBlockSize;
            if (bufferSize > 4096) bufferSize = 4096;
            if (bufferSize < 512) bufferSize = 512;
            FileOutputStream foutput = new FileOutputStream(temp);
            output = new BufferedOutputStream(foutput, bufferSize);
            if (read == buffer.length && ((flags & DropBoxManager.IS_GZIPPED) == 0)) {
                output = new GZIPOutputStream(output);
                flags = flags | DropBoxManager.IS_GZIPPED;
            }
}


6. 更改 /data/anr/trace.txt 的文件名：更改文件名中包含process name:可以从中提取出来
//Set the trace file name to app name + current date format to avoid overrinding trace file
String tracesPath = SystemProperties.get("dalvik.vm.stack-trace-file", null);
if (tracesPath != null && tracesPath.length() != 0) {
   File traceRenameFile = new File(tracesPath);
   String newTracesPath;
   int lpos = tracesPath.lastIndexOf (".");
   if (-1 != lpos)
  newTracesPath = tracesPath.substring (0, lpos) + "_" + app.processName + "_" + mTraceDateFormat.format(new Date()) + tracesPath.substring (lpos);
   else
      newTracesPath = tracesPath + "_" + app.processName;
   traceRenameFile.renameTo(new File(newTracesPath));
}




7. /data/anr/traces.txt文件的内容
和/data/system/dropbox的压缩文件[e-mail]
的内容是不同的：
/data/anr/traces.txt是 java进程下各个线程的栈；可能不只是当前进程；
dropbox中还有其他的内容如：cpu占用率等和logcat的比较像，也包含部分栈信息(可能有大小的限制)