Android12系統源碼分析：NativeTombstoneManager
概述
android12新增的system_server程序（LocalService）本地服務，用于管理native tombstones。
該服務在開機Systemerver初始化流程啟動，添加到LocalService，然後啟動一個ServiceThread線程用于（mHandler.post）處理本服務的業務。
NativeTombstoneManager的功能主要是：
- 監聽
/data/tombstones
- 特定tombstones檔案删除
- 特定tombstones檔案檢索
值得關注的是AMS對該服務的使用，也是Android11新增API：
getHistoricalProcessExitReasons()
軟體架構如圖：
圖：NativeTombstoneManager類圖
啟動流程
圖：NativeTombstoneManager服務啟動時序圖
服務比較簡單，和其他SystemServer啟動的服務一樣，
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManagerService.java
public class NativeTombstoneManagerService extends SystemService {
private NativeTombstoneManager mManager;
@Override
public void onStart() {
mManager = new NativeTombstoneManager(getContext());
//僅添加本地服務，沒有binder服務
LocalServices.addService(NativeTombstoneManager.class, mManager);
}
@Override
public void onBootPhase(int phase) {
if (phase == SystemService.PHASE_ACTIVITY_MANAGER_READY) {
mManager.onSystemReady();
}
}
}
本服務也是SystemService工具類的子類，通過重寫onStart、onBootPhase獲得代碼流程
在onStart中初始化真正的服務實作NativeTombstoneManager，執行個體化後添加到LocalServices
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
public final class NativeTombstoneManager {
NativeTombstoneManager(Context context) {
//啟動handler線程，用于後續處理本服務的業務
final ServiceThread thread = new ServiceThread(TAG + ":tombstoneWatcher",
THREAD_PRIORITY_BACKGROUND, true /* allowIo */);
thread.start();
mHandler = thread.getThreadHandler();
//啟動檔案監聽/data/tombstones
mWatcher = new TombstoneWatcher();
mWatcher.startWatching();
}
void onSystemReady() {
registerForUserRemoval();
registerForPackageRemoval();
// 開機階段先掃描一次/data/tombstones目錄
mHandler.post(() -> {
final File[] tombstoneFiles = TOMBSTONE_DIR.listFiles();
for (int i = 0; tombstoneFiles != null && i < tombstoneFiles.length; i++) {
if (tombstoneFiles[i].isFile()) {
handleTombstone(tombstoneFiles[i]);
開機流程有三個動作
- 啟動handler線程，用于後續處理本服務的業務
- TombstoneWatcher啟動檔案監聽/data/tombstones
- 開機階段先掃描一次/data/tombstones目錄
看一下handleTombstone
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
private void handleTombstone(File path) {
final String filename = path.getName();
if (!filename.startsWith("tombstone_")) {
return;
}
if (filename.endsWith(".pb")) {
handleProtoTombstone(path);
BootReceiver.addTombstoneToDropBox(mContext, path, true);
} else {
BootReceiver.addTombstoneToDropBox(mContext, path, false);
如果是以pb結尾的原型檔案，則handleProtoTombstone方法中為該檔案生成TombstoneFile對象，并添加到資料結構
private final SparseArray<TombstoneFile> mTombstones;
并且，每個新生成的tombstone檔案都會同步給dropbox
新檔案的監聽
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
class TombstoneWatcher extends FileObserver {
TombstoneWatcher() {
super(TOMBSTONE_DIR, FileObserver.CREATE | FileObserver.MOVED_TO);
}
@Override
public void onEvent(int event, @Nullable String path) {
mHandler.post(() -> {
handleTombstone(new File(TOMBSTONE_DIR, path));
});
内部類TombstoneWatcher，當目錄/data/tombstones有檔案生成時，回調到onEvent，然後通過handleTombstone方法做處理
AciivtyManager#getHistoricalProcessExitReasons
圖：getHistoricalProcessExitReasons方法時序圖
需要注意傳回的資料結構的處理ApplicationExitInfo。
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
public void collectTombstones(ArrayList<ApplicationExitInfo> output, int callingUid, int pid,
int maxNum) {
CompletableFuture<Object> future = new CompletableFuture<>();
if (!UserHandle.isApp(callingUid)) {
return;
}
final int userId = UserHandle.getUserId(callingUid);
final int appId = UserHandle.getAppId(callingUid);
mHandler.post(() -> {
boolean appendedTombstones = false;
synchronized (mLock) {
final int tombstonesSize = mTombstones.size();
tombstoneIter:
//周遊所有已知tombstoe，
//如果userid和appid和reason比對
//則傳回請求的數量的tombstone
for (int i = 0; i < tombstonesSize; ++i) {
TombstoneFile tombstone = mTombstones.valueAt(i);
if (tombstone.matches(Optional.of(userId), Optional.of(appId))) {
if (pid != 0 && tombstone.mPid != pid) {
continue;
}
//reason判斷
// Try to attach to an existing REASON_CRASH_NATIVE.
final int outputSize = output.size();
for (int j = 0; j < outputSize; ++j) {
ApplicationExitInfo exitInfo = output.get(j);
if (tombstone.matches(exitInfo)) {
exitInfo.setNativeTombstoneRetriever(tombstone.getPfdRetriever());
continue tombstoneIter;
}
}
//請求數量判斷
if (output.size() < maxNum) {
appendedTombstones = true;
output.add(tombstone.toAppExitInfo());
}
}
}
}
//如果超過一個則按時間戳排序
if (appendedTombstones) {
Collections.sort(output, (lhs, rhs) -> {
// Reports should be ordered with newest reports first.
long diff = rhs.getTimestamp() - lhs.getTimestamp();
if (diff < 0) {
return -1;
} else if (diff == 0) {
return 0;
} else {
return 1;
}
});
}
future.complete(null);
});
try {
future.get();
周遊所有已知tombstoe，如果userid和appid和reason比對則傳回請求的數量的tombstone
如果數量超過一個則按時間戳排序
值得注意的是CompletableFuture，函數式程式設計，可參考：CompletableFuture基本用法
tombstone檔案的清理
目前有兩種場景會清理檔案
- 主動調用接口删除，AppExitInfoTracker-->purge()
- app被解除安裝時，registerForPackageRemoval-->purgePackage()-->purge()
clearHistoryProcessExitInfo
frameworks/base/services/core/java/com/android/server/am/AppExitInfoTracker.java
void clearHistoryProcessExitInfo(String packageName, int userId) {
NativeTombstoneManager tombstoneService = LocalServices.getService(
NativeTombstoneManager.class);
Optional<Integer> appId = Optional.empty();
if (TextUtils.isEmpty(packageName)) {
synchronized (mLock) {
removeByUserIdLocked(userId);
}
} else {
final int uid = mService.mPackageManagerInt.getPackageUid(packageName,
PackageManager.MATCH_ALL, userId);
appId = Optional.of(UserHandle.getAppId(uid));
synchronized (mLock) {
removePackageLocked(packageName, uid, true, userId);
}
}
tombstoneService.purge(Optional.of(userId), appId);
schedulePersistProcessExitInfo(true);
}
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
* Remove native tombstones matching a user and/or app.
public void purge(Optional<Integer> userId, Optional<Integer> appId) {
mHandler.post(() -> {
synchronized (mLock) {
for (int i = mTombstones.size() - 1; i >= 0; --i) {
TombstoneFile tombstone = mTombstones.valueAt(i);
if (tombstone.matches(userId, appId)) {
tombstone.purge();
mTombstones.removeAt(i);
----------------------------------------------------------------------
static class TombstoneFile {
public void purge() {
if (!mPurged) {
try {
Os.ftruncate(mPfd.getFileDescriptor(), 0);
} catch (ErrnoException ex) {
Slog.e(TAG, "Failed to truncate tombstone", ex);
}
mPurged = true;
purgePackage
frameworks/base/services/core/java/com/android/server/os/NativeTombstoneManager.java
private void registerForPackageRemoval() {
final IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_PACKAGE_FULLY_REMOVED);
filter.addDataScheme("package");
mContext.registerReceiverForAllUsers(new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
final int uid = intent.getIntExtra(Intent.EXTRA_UID, UserHandle.USER_NULL);
if (uid == UserHandle.USER_NULL) return;
final boolean allUsers = intent.getBooleanExtra(
Intent.EXTRA_REMOVED_FOR_ALL_USERS, false);
purgePackage(uid, allUsers);
}
}, filter, null, mHandler);
}
---------------------------------------------
private void purgePackage(int uid, boolean allUsers) {
final int appId = UserHandle.getAppId(uid);
Optional<Integer> userId;
if (allUsers) {
userId = Optional.empty();
} else {
userId = Optional.of(UserHandle.getUserId(uid));
}
purge(userId, Optional.of(appId));
}
private void purgeUser(int uid) {
purge(Optional.of(uid), Optional.empty());
}
f服務啟動時registerForPackageRemoval調用，開啟對廣播的監聽：ACTION_PACKAGE_FULLY_REMOVED
當app解除安裝時，此處也删除其對應uid的tombstone檔案
同這個包删除類似，還有使用者删除時也會删對應的檔案：
private void registerForUserRemoval() {
filter.addAction(Intent.ACTION_USER_REMOVED);