发生ANR之后的事情

触发ANR条件

Service Timeout:前台服务20s内未完成执行，后台服务超过200sBroadcastQueue Timeout：前台广播在10s内未完成,后台广播超过60s未完成ContentProvider Timeout：内容提供者,在publish过超时10sInputDispatching Timeout: 输入事件分发超时5s，包括按键和触摸事件

对应最后执行ANR记录的方法是：

ActiveServices.serviceTimeout()BroadcastQueue.AppNotResponding.run().appNotResponding()AMS.appNotRespondingViaProvider()AMS.inputDispatchingTimedOut()

理解为什么会出发ANR，必须明白四大组件的启动流程。这个我们以后分析。

分析ANR触发之后记录问题

可以将anr目录下的文件放到电脑上进行查看 adb pull data/anr .

属性系统可以通过adb shell getprop dalvik.vm.stack-trace-file这种方式查找对应的属性值

当触发ANR之后会调用AppErrors.appNotResponding()方法

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); ... //记录ANR时间 long anrTime = SystemClock.uptimeMillis(); //更新CPU状态 if (ActivityManagerService.MONITOR_CPU_USAGE) { mService.updateCpuStatsNow(); } //特定场景下忽略ANR synchronized (mService) { if (mService.mShuttingDown) { Slog.i(TAG, "During shutdown skipping ANR: " + app + " " + annotation); return; } else if (app.notResponding) { Slog.i(TAG, "Skipping duplicate ANR: " + app + " " + annotation); return; } else if (app.crashing) { Slog.i(TAG, "Crashing app skipping ANR: " + app + " " + annotation); return; } } //为了防止多次对相同app的anr执行重复代码，在此处标注记录，属于上面的特定情况种的一种 app.notResponding = true; //记录ANR信息到Event Log中 EventLog.writeEvent(EventLogTags.AM_ANR, app.userId, app.pid, app.processName, app.info.flags, annotation); //添加当前app到firstpids列表中 firstPids.add(app.pid); //如果可能添加父进程到firstpids列表种 int parentPid = app.pid; ... // 将ANR信息存在info变量中，后续打印到LOGCAT，这部分的信息会以ActivityManager为Tag打印出来，包含了ANR的进程，出现原因以及当时的CPU状态，这些对分析ANR是非常重要的信息 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"); } //将ANR信息输出到traces文件，分为两种，一种带native层信息，一种不带 ProcessCpuTracker processCpuTracker = new ProcessCpuTracker(true; String[] nativeProcs = NATIVE_STACKS_OF_INTEREST; // don't dump native PIDs for background ANRs File tracesFile = null; if (isSilentANR) { //这里返回了一个文件，这里的文件路径是：`/data/anr/traces.txt` //查找方法：adb shell getprop dalvik.vm.stack-trace-file tracesFile = mService.dumpStackTraces(true, firstPids, null, lastPids, null); } else { tracesFile = mService.dumpStackTraces(true, firstPids, processCpuTracker, lastPids, nativeProcs); } //再次更新CPU信息，并且输出到SystemLog中 String cpuInfo = null; if (ActivityManagerService.MONITOR_CPU_USAGE) { mService.updateCpuStatsNow(); synchronized (mService.mProcessCpuTracker) { cpuInfo = mService.mProcessCpuTracker.printCurrentState(anrTime); } info.append(processCpuTracker.printCurrentLoad()); info.append(cpuInfo); } info.append(processCpuTracker.printCurrentState(anrTime)); Slog.e(TAG, info.toString()); //上面的信息已经对应的ANR信息写入/data/anr/traces.txt中 //给底层发送信号Process.SIGNAL_QUIT=3 if (tracesFile == null) { Process.sendSignal(app.pid, Process.SIGNAL_QUIT); } //将traces文件 和 CPU使用率信息保存到dropbox，即data/system/dropbox目录 //命名：system_server/system_app/data_app + type+...比如下面 //data_app_anr@1501989621992.txt.gz //data_app_crash@1501989671926.txt mService.addErrorToDropBox("anr", app, app.processName, activity, parent, annotation, cpuInfo, tracesFile, null); synchronized (mService) { mService.mBatteryStatsService.noteProcessAnr(app.processName, app.uid); //如果是后台ANR则直接杀掉结束 if (isSilentANR) { app.kill("bg anr", true); return; } //设置app的not响应状态，并查找errorReportReceiver makeAppNotRespondingLocked(app, activity != null ? activity.shortComponentName : null, annotation != null ? "ANR " + annotation : "ANR", info.toString()); //弹出ANR对话框 Message msg = Message.obtain(); HashMap<String, Object> map = new HashMap<String, Object>(); msg.what = ActivityManagerService.SHOW_NOT_RESPONDING_UI_MSG; msg.obj = map; msg.arg1 = aboveSystem ? 1 : 0; map.put("app", app); if (activity != null) { map.put("activity", activity); } //向ui线程发送，内容为SHOW_NOT_RESPONDING_MSG的消息 mService.mUiHandler.sendMessage(msg); } }

我们来小节一下上面发生了什么：

立刻更新了CPU的信息 java /** 2721 cpu (total|1|6),(user|1|6),(system|1|6),(iowait|1|6),(irq|1|6),(softirq|1|6) */ public static final int CPU = 2721; 给event_log中写入值 忽略一些anr在event_log中打印am_anr的信息，这个是anr立刻发生的记录将ANR信息存在info变量中，后续打印到LOGCAT，这部分的信息会以ActivityManager为Tag打印出来，包含了ANR的进程，出现原因以及当时的CPU状态，这些对分析ANR是非常重要的信息将ANR信息输出到data/anr/traces文件没有输出到traces文件的时候，给底层发送一个rocess.SIGNAL_QUIT=3信号将traces文件 和 CPU使用率信息保存到dropbox，即data/system/dropbox目录如果是后台ANR则直接杀掉结束弹出ANR对话框

细节

怎么样就将信息保存到了/data/anr/traces.txt了

1.AMS.dumpStackTraces

public static File dumpStackTraces(boolean clearTraces, ArrayList<Integer> firstPids, ProcessCpuTracker processCpuTracker, SparseArray<Boolean> lastPids, String[] nativeProcs) { //tracesPath = "data/anr/traces.txt" String tracesPath = SystemProperties.get("dalvik.vm.stack-trace-file", null); if (tracesPath == null || tracesPath.length() == 0) { return null; } File tracesFile = new File(tracesPath); try { 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; } //[2] dumpStackTraces(tracesPath, firstPids, processCpuTracker, lastPids, nativeProcs); return tracesFile; }

2.

private static void dumpStackTraces(String tracesPath, ArrayList<Integer> firstPids, ProcessCpuTracker processCpuTracker, SparseArray<Boolean> lastPids, String[] nativeProcs){ FileObserver observer = new FileObserver(tracesPath, FileObserver.CLOSE_WRITE) { @Override public synchronized void onEvent(int event, String path) { notify(); } }; try { observer.startWatching(); // 获取发生ANR进程的pid,然后遍历这些进程给进程发送Process.SIGNAL_QUIT=3的信号 if (firstPids != null) { try { int num = firstPids.size(); for (int i = 0; i < num; i++) { synchronized (observer) { final long sime = SystemClock.elapsedRealtime(); Process.sendSignal(firstPids.get(i), Process.SIGNAL_QUIT); observer.wait(1000); // Wait for write-close, give up after 1 sec } } } catch (InterruptedException e) { Slog.wtf(TAG, e); } } // 接下来收集本地pids的堆栈 if (nativeProcs != null) { int[] pids = Process.getPidsForCommands(nativeProcs); if (pids != null) { for (int pid : pids) { final long sime = SystemClock.elapsedRealtime(); Debug.dumpNativeBacktraceToFileTimeout(pid, tracesPath, 10);//[3]输出native进程的trace并且限制超时时间 } } } 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(); //从lastPids中选取CPU使用率 top 5的进程，输出这些进程的stacks 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) { final long stime = SystemClock.elapsedRealtime(); Process.sendSignal(stats.pid, Process.SIGNAL_QUIT); observer.wait(1000); // Wait for write-close, give up after 1 sec } } catch (InterruptedException e) { Slog.wtf(TAG, e); } } else if (DEBUG_ANR) { Slog.d(TAG, "Skipping next CPU consuming process, not a java proc: " + stats.pid); } } } } finally { observer.stopWatching(); } }

小结：

收集发生anr进程的调用栈

发生anr的进程anr进程的父进程（anr进程是由于AMS生成，AMS在system_server进程中，system_server进程是anr的父进程）mLruProcesses中所有的persistent进程

收集Native进程的调用栈

"/system/bin/audioserver""/system/bin/cameraserver""/system/bin/drmserver""/system/bin/mediadrmserver""/system/bin/mediaserver""/system/bin/sdcard""/system/bin/surfaceflinger""media.codec" // system/bin/mediacodec"media.extractor" // system/bin/mediaextractor"com.android.bluetooth" // Bluetooth service收集lastPids进程的stacks 收集前五名

注意收集信息等待的时间

3.Debug.dumpNativeBacktraceToFileTimeout()

static void android_os_Debug_dumpNativeBacktraceToFileTimeout(JNIEnv* env, jobject clazz, jint pid, jstring fileName, jint timeoutSecs) { if (fileName == NULL) { jniThrowNullPointerException(env, "file == null"); return; } const jchar* str = env->GetStringCritical(fileName, 0); String8 fileName8; if (str) { fileName8 = String8(reinterpret_cast<const char16_t*>(str), env->GetStringLength(fileName)); env->ReleaseStringCritical(fileName, str); } //打开文件(data/anr/traces.txt) int fd = open(fileName8.string(), O_CREAT | O_WRONLY | O_NOFOLLOW | O_CLOEXEC | O_APPEND, 0666); if (fd < 0) { fprintf(stderr, "Can't open %s: %s\n", fileName8.string(), strerror(errno)); return; } dump_backtrace_to_file_timeout(pid, fd, timeoutSecs);//[4] close(fd); }

4.dump_backtrace_to_file_timeout()

int dump_backtrace_to_file_timeout(pid_t tid, int fd, int timeout_secs) { //发送dump请求得到sock_fd int sock_fd = make_dump_request(DEBUGGER_ACTION_DUMP_BACKTRACE, tid, timeout_secs); if (sock_fd < 0) { return -1; } int result = 0; char buffer[1024]; ssize_t n; int flag = 0; //从sock_fd中读取信息写入data/anr/traces.txt中 while ((n = TEMP_FAILURE_RETRY(read(sock_fd, buffer, sizeof(buffer)))) > 0) { flag = 1; if (TEMP_FAILURE_RETRY(write(fd, buffer, n)) != n) { result = -1; break; } } close(sock_fd); ... return result; }

主要是通过给底层发送DEBUGGER_ACTION_DUMP_BACKTRACE来请求dump的sock_fd句柄，底层调用dump_backtraces()来获取信息，从而写入data/anr/traces.txt文件中

总结

当发生anr的时候，距离ANR最近的时间是am_anr这个日志的时间，然后会打印各种信息有底层dump的，有进程的调用栈信息等等。最后将trances.txt写入data/system/dropbox目录下，并且重命名，规则见上文。

补充

其中Process.sendSignal(stats.pid, Process.SIGNAL_QUIT);发出退出进程信号