ActivityThread#handlePauseActivity：主要完成三件事，一是通过userLeaving标志决定是否向即将Pause的组件发送一个用户离开事件的通知，最终会调用到activity的performUserLeaving函数；二是调用performPauseActivityItem函数向即将Pause的组件发送一个中止事件通知，最终会调用到activity的onPause函数；三是调用QueuedWork类的静态成员函数waitToFinish等待完成前面的一些数据写入操作。由于该组件即将进入Paused状态了，因此要保证它前面的所有数据写入操作都处理完成，否则，等到它重新进入resumed状态时，就无法恢复之前所保存的一些状态数据了。
可以判断next页面是否已经被系统回收，如果是false就代表页面被回收了走else分支，调用StackSupervisor的startSpecificActivityLocked重启页面。如果是true，那么就会通过TransactionExecutor调度执行ResumeActivityItem的execute方法，执行前一个页面的onResume方法。
ActivityStackSupervisor.java services\core\java\com\android\server\wm +
ActivityStackSupervisor，顾名思义，就是用来管理ActivityStack的。
getProcessController，根据进程名获取Activity所在的进程的WindowProcessController对象，如果返回值不为null，说明Activity所在的应用进程已经启动，直接调用realStartActivityLocked，否则向ActivityTaskManagerService的mH发送启动应用程序进程的消息。
void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {
// Is this activity's application already running? 判断activity 的 application 是否已经启动
final WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);
//getProcessController，根据进程名获取Activity所在的进程的WindowProcessController对象
boolean knownToBeDead = false;
if (wpc != null && wpc.hasThread()) {
try {
realStartActivityLocked(r, wpc, andResume, checkConfig);//如果返回值不为null，说明Activity所在的应用进程已经启动，直接调用realStartActivityLocked
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity "
+ r.intent.getComponent().flattenToShortString(), e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
knownToBeDead = true;
}
r.notifyUnknownVisibilityLaunchedForKeyguardTransition();
final boolean isTop = andResume && r.isTopRunningActivity();
mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");//重新启动进程~
}
startProcessAsync 作用是发个消息给AMS，告诉它启动一个进程，具体是通过调用startProcess这个方法，在ActivityManagerInternal 中声明，AMS内部的LocalService来实现具体逻辑。
具体实现是AMS 里的startProcess
void startProcessAsync(ActivityRecord activity, boolean knownToBeDead, boolean isTop,
String hostingType) {
try {
if (Trace.isTagEnabled(TRACE_TAG_WINDOW_MANAGER)) {
Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "dispatchingStartProcess:"
+ activity.processName);
}
// Post message to start process to avoid possible deadlock of calling into AMS with the
// ATMS lock held.发布消息以启动进程，以避免在持有 ATMS 锁的情况下调用 AMS 可能出现死锁。
final Message m = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess,
mAmInternal, activity.processName, activity.info.applicationInfo, knownToBeDead,
isTop, hostingType, activity.intent.getComponent());
mH.sendMessage(m);
} finally {
Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
}
}
ActivityManagerService.java services\core\java\com\android\server\am
AMS管理三大组件，以及进程的创建等。
@Override
public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead,
boolean isTop, String hostingType, ComponentName hostingName) {
try {
if (Trace.isTagEnabled(Trace.TRACE_TAG_ACTIVITY_MANAGER)) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "startProcess:"
+ processName);
}
synchronized (ActivityManagerService.this) {
// If the process is known as top app, set a hint so when the process is
// started, the top priority can be applied immediately to avoid cpu being
// preempted by other processes before attaching the process of top app.
//如果进程被称为top app，设置一个hint，这样当进程启动时，可以立即应用最高优先级，
//以避免在附加top app的进程之前cpu被其他进程抢占。
startProcessLocked(processName, info, knownToBeDead, 0 /* intentFlags */,
new HostingRecord(hostingType, hostingName, isTop),
ZYGOTE_POLICY_FLAG_LATENCY_SENSITIVE, false /* allowWhileBooting */,
false /* isolated */, true /* keepIfLarge */);
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
}
@GuardedBy("this")
final ProcessRecord startProcessLocked(String processName,
ApplicationInfo info, boolean knownToBeDead, int intentFlags,
HostingRecord hostingRecord, int zygotePolicyFlags, boolean allowWhileBooting,
boolean isolated, boolean keepIfLarge) {
return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags,
hostingRecord, zygotePolicyFlags, allowWhileBooting, isolated, 0 /* isolatedUid */,
keepIfLarge, null /* ABI override */, null /* entryPoint */,
null /* entryPointArgs */, null /* crashHandler */);//调用类型为ProcessList的成员mProcessList的内部方法
}
ProcessList.java services\core\java\com\android\server\am
从Android 10.0开始，startProcess的核心逻辑就从AMS转移到ProcessList中，把进程启动相关逻辑放到进程管理的相关类中。
ProcessList#startProcessLocked：调用getProcessRecordLocked获取ProcessRecord进程信息记录对象实例，若返回值不为null，则判断进程是否正在运行，若正在运行则直接返回该对象实例，若不在运行则清除该对象实例数据信息，直接复用。若返回值为null，则调用newProcessRecordLocked来创建一个新的实例用于记录即将启动的进程的相关信息。
@GuardedBy("mService")
final ProcessRecord startProcessLocked(String processName, ApplicationInfo info,
boolean knownToBeDead, int intentFlags, HostingRecord hostingRecord,
int zygotePolicyFlags, boolean allowWhileBooting, boolean isolated, int isolatedUid,
boolean keepIfLarge, String abiOverride, String entryPoint, String[] entryPointArgs,
Runnable crashHandler) {
long startTime = SystemClock.uptimeMillis();
ProcessRecord app;
if (!isolated) {//传入的isolated为false
app = getProcessRecordLocked(processName, info.uid, keepIfLarge);//获取ProcessRecord实例，一般来说获取不到的
checkSlow(startTime, "startProcess: after getProcessRecord");
if ((intentFlags & Intent.FLAG_FROM_BACKGROUND) != 0) {
// If we are in the background, then check to see if this process
// is bad. If so, we will just silently fail.如果我们在后台，那么检查这个进程是不是坏的。 如果是这样，我们只会默默地失败。
if (mService.mAppErrors.isBadProcess(info.processName, info.uid)) {
if (DEBUG_PROCESSES) Slog.v(TAG, "Bad process: " + info.uid
+ "/" + info.processName);
return null;
}
} else {
// When the user is explicitly starting a process, then clear its
// crash count so that we won't make it bad until they see at
// least one crash dialog again, and make the process good again
// if it had been bad.
//当用户明确启动一个进程时，清除它的崩溃计数，这样我们就不会让它变坏，
//直到他们再次看到至少一个崩溃对话框，如果它已经坏了，我们就让它再次变好。
if (DEBUG_PROCESSES) Slog.v(TAG, "Clearing bad process: " + info.uid
+ "/" + info.processName);
mService.mAppErrors.resetProcessCrashTimeLocked(info);
if (mService.mAppErrors.isBadProcess(info.processName, info.uid)) {
EventLog.writeEvent(EventLogTags.AM_PROC_GOOD,
UserHandle.getUserId(info.uid), info.uid,
info.processName);
mService.mAppErrors.clearBadProcess(info.processName, info.uid);
if (app != null) {
app.bad = false;
}
}
}
} else {
// If this is an isolated process, it can't re-use an existing process.
//如果这是一个孤立的进程，它不能重用现有的进程。
app = null;
}
// We don't have to do anything more if:
// (1) There is an existing application record; and
// (2) The caller doesn't think it is dead, OR there is no thread
// object attached to it so we know it couldn't have crashed; and
// (3) There is a pid assigned to it, so it is either starting or
// already running.
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES, "startProcess: name=" + processName
+ " app=" + app + " knownToBeDead=" + knownToBeDead
+ " thread=" + (app != null ? app.thread : null)
+ " pid=" + (app != null ? app.pid : -1));
ProcessRecord precedence = null;
if (app != null && app.pid > 0) {
if ((!knownToBeDead && !app.killed) || app.thread == null) {
// We already have the app running, or are waiting for it to
// come up (we have a pid but not yet its thread), so keep it.
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES, "App already running: " + app);
// If this is a new package in the process, add the package to the list
app.addPackage(info.packageName, info.longVersionCode, mService.mProcessStats);
checkSlow(startTime, "startProcess: done, added package to proc");
return app;
}
// An application record is attached to a previous process,
// clean it up now.
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES, "App died: " + app);
checkSlow(startTime, "startProcess: bad proc running, killing");
ProcessList.killProcessGroup(app.uid, app.pid);
checkSlow(startTime, "startProcess: done killing old proc");
Slog.wtf(TAG_PROCESSES, app.toString() + " is attached to a previous process");
// We are not going to re-use the ProcessRecord, as we haven't dealt with the cleanup
// routine of it yet, but we'd set it as the precedence of the new process.
precedence = app;
app = null;
}
if (app == null) {
checkSlow(startTime, "startProcess: creating new process record");
app = newProcessRecordLocked(info, processName, isolated, isolatedUid, hostingRecord);//新建一个ProcessRecord对象
if (app == null) {
Slog.w(TAG, "Failed making new process record for "
+ processName + "/" + info.uid + " isolated=" + isolated);
return null;
}
app.crashHandler = crashHandler;
app.isolatedEntryPoint = entryPoint;
app.isolatedEntryPointArgs = entryPointArgs;
if (precedence != null) {
app.mPrecedence = precedence;
precedence.mSuccessor = app;
}
checkSlow(startTime, "startProcess: done creating new process record");
} else {
// If this is a new package in the process, add the package to the list
app.addPackage(info.packageName, info.longVersionCode, mService.mProcessStats);
checkSlow(startTime, "startProcess: added package to existing proc");
}
// If the system is not ready yet, then hold off on starting this
// process until it is.
//如果系统还没有准备好，那么在它准备好之前不要启动这个进程
if (!mService.mProcessesReady
&& !mService.isAllowedWhileBooting(info)
&& !allowWhileBooting) {
if (!mService.mProcessesOnHold.contains(app)) {
mService.mProcessesOnHold.add(app);
}
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES,
"System not ready, putting on hold: " + app);
checkSlow(startTime, "startProcess: returning with proc on hold");
return app;
}
checkSlow(startTime, "startProcess: stepping in to startProcess");
final boolean success =
startProcessLocked(app, hostingRecord, zygotePolicyFlags, abiOverride);//根据ProcessRecord对象去fork出新的进程
checkSlow(startTime, "startProcess: done starting proc!");
return success ? app : null;
}
/**
* @return {@code true} if process start is successful, false otherwise.
*/
@GuardedBy("mService")
boolean startProcessLocked(ProcessRecord app, HostingRecord hostingRecord,
int zygotePolicyFlags, boolean disableHiddenApiChecks, boolean disableTestApiChecks,
boolean mountExtStorageFull, String abiOverride) {
if (app.pendingStart) {
return true;
}
long startTime = SystemClock.uptimeMillis();
if (app.pid > 0 && app.pid != ActivityManagerService.MY_PID) {
checkSlow(startTime, "startProcess: removing from pids map");
mService.removePidLocked(app);
app.bindMountPending = false;
mService.mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
checkSlow(startTime, "startProcess: done removing from pids map");
app.setPid(0);
app.startSeq = 0;
}
if (DEBUG_PROCESSES && mService.mProcessesOnHold.contains(app)) Slog.v(
TAG_PROCESSES,
"startProcessLocked removing on hold: " + app);
mService.mProcessesOnHold.remove(app);
checkSlow(startTime, "startProcess: starting to update cpu stats");
mService.updateCpuStats();//更新CPU时间
checkSlow(startTime, "startProcess: done updating cpu stats");
try {
try {
final int userId = UserHandle.getUserId(app.uid);
AppGlobals.getPackageManager().checkPackageStartable(app.info.packageName, userId);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
int uid = app.uid;
int[] gids = null;
int mountExternal = Zygote.MOUNT_EXTERNAL_NONE;
if (!app.isolated) {
int[] permGids = null;
try {
checkSlow(startTime, "startProcess: getting gids from package manager");
final IPackageManager pm = AppGlobals.getPackageManager();
permGids = pm.getPackageGids(app.info.packageName,
MATCH_DIRECT_BOOT_AUTO, app.userId);
StorageManagerInternal storageManagerInternal = LocalServices.getService(
StorageManagerInternal.class);
mountExternal = storageManagerInternal.getExternalStorageMountMode(uid,
app.info.packageName);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
// Remove any gids needed if the process has been denied permissions.
// NOTE: eventually we should probably have the package manager pre-compute
// this for us?
if (app.processInfo != null && app.processInfo.deniedPermissions != null) {
for (int i = app.processInfo.deniedPermissions.size() - 1; i >= 0; i--) {
int[] denyGids = mService.mPackageManagerInt.getPermissionGids(
app.processInfo.deniedPermissions.valueAt(i), app.userId);
if (denyGids != null) {
for (int gid : denyGids) {
permGids = ArrayUtils.removeInt(permGids, gid);
}
}
}
}
gids = computeGidsForProcess(mountExternal, uid, permGids);
}
app.mountMode = mountExternal;
checkSlow(startTime, "startProcess: building args");
if (mService.mAtmInternal.isFactoryTestProcess(app.getWindowProcessController())) {
uid = 0;
}
int runtimeFlags = 0;
if ((app.info.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
runtimeFlags |= Zygote.DEBUG_ENABLE_JDWP;
runtimeFlags |= Zygote.DEBUG_JAVA_DEBUGGABLE;
// Also turn on CheckJNI for debuggable apps. It's quite
// awkward to turn on otherwise.
runtimeFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
// Check if the developer does not want ART verification
if (android.provider.Settings.Global.getInt(mService.mContext.getContentResolver(),
android.provider.Settings.Global.ART_VERIFIER_VERIFY_DEBUGGABLE, 1) == 0) {
runtimeFlags |= Zygote.DISABLE_VERIFIER;
Slog.w(TAG_PROCESSES, app + ": ART verification disabled");
}
}
// Run the app in safe mode if its manifest requests so or the
// system is booted in safe mode.
// 如果其清单请求或系统以安全模式启动，则以安全模式运行应用程序。
if ((app.info.flags & ApplicationInfo.FLAG_VM_SAFE_MODE) != 0 || mService.mSafeMode) {
runtimeFlags |= Zygote.DEBUG_ENABLE_SAFEMODE;
}
if ((app.info.privateFlags & ApplicationInfo.PRIVATE_FLAG_PROFILEABLE_BY_SHELL) != 0) {
runtimeFlags |= Zygote.PROFILE_FROM_SHELL;
}
if ("1".equals(SystemProperties.get("debug.checkjni"))) {
runtimeFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
String genDebugInfoProperty = SystemProperties.get("debug.generate-debug-info");
if ("1".equals(genDebugInfoProperty) || "true".equals(genDebugInfoProperty)) {
runtimeFlags |= Zygote.DEBUG_GENERATE_DEBUG_INFO;
}
String genMiniDebugInfoProperty = SystemProperties.get("dalvik.vm.minidebuginfo");
if ("1".equals(genMiniDebugInfoProperty) || "true".equals(genMiniDebugInfoProperty)) {
runtimeFlags |= Zygote.DEBUG_GENERATE_MINI_DEBUG_INFO;
}
if ("1".equals(SystemProperties.get("debug.jni.logging"))) {
runtimeFlags |= Zygote.DEBUG_ENABLE_JNI_LOGGING;
}
if ("1".equals(SystemProperties.get("debug.assert"))) {
runtimeFlags |= Zygote.DEBUG_ENABLE_ASSERT;
}
if ("1".equals(SystemProperties.get("debug.ignoreappsignalhandler"))) {
runtimeFlags |= Zygote.DEBUG_IGNORE_APP_SIGNAL_HANDLER;
}
if (mService.mNativeDebuggingApp != null
&& mService.mNativeDebuggingApp.equals(app.processName)) {
// Enable all debug flags required by the native debugger.
// 启用本机调试器所需的所有调试标志。
runtimeFlags |= Zygote.DEBUG_ALWAYS_JIT; // Don't interpret anything
runtimeFlags |= Zygote.DEBUG_GENERATE_DEBUG_INFO; // Generate debug info
runtimeFlags |= Zygote.DEBUG_NATIVE_DEBUGGABLE; // Disbale optimizations
mService.mNativeDebuggingApp = null;
}
if (app.info.isEmbeddedDexUsed()
|| (app.info.isPrivilegedApp()
&& DexManager.isPackageSelectedToRunOob(app.pkgList.mPkgList.keySet()))) {
runtimeFlags |= Zygote.ONLY_USE_SYSTEM_OAT_FILES;
}
if (!disableHiddenApiChecks && !mService.mHiddenApiBlacklist.isDisabled()) {
app.info.maybeUpdateHiddenApiEnforcementPolicy(
mService.mHiddenApiBlacklist.getPolicy());
@ApplicationInfo.HiddenApiEnforcementPolicy int policy =
app.info.getHiddenApiEnforcementPolicy();
int policyBits = (policy << Zygote.API_ENFORCEMENT_POLICY_SHIFT);
if ((policyBits & Zygote.API_ENFORCEMENT_POLICY_MASK) != policyBits) {
throw new IllegalStateException("Invalid API policy: " + policy);
}
runtimeFlags |= policyBits;
if (disableTestApiChecks) {
runtimeFlags |= Zygote.DISABLE_TEST_API_ENFORCEMENT_POLICY;
}
}
String useAppImageCache = SystemProperties.get(
PROPERTY_USE_APP_IMAGE_STARTUP_CACHE, "");
// Property defaults to true currently.
// 属性当前默认为 true。
if (!TextUtils.isEmpty(useAppImageCache) && !useAppImageCache.equals("false")) {
runtimeFlags |= Zygote.USE_APP_IMAGE_STARTUP_CACHE;
}
runtimeFlags |= decideGwpAsanLevel(app);
String invokeWith = null;
if ((app.info.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
// Debuggable apps may include a wrapper script with their library directory.
// 可调试的应用程序可能包含一个包装脚本及其库目录。
String wrapperFileName = app.info.nativeLibraryDir + "/wrap.sh";
StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
try {
if (new File(wrapperFileName).exists()) {
invokeWith = "/system/bin/logwrapper " + wrapperFileName;
}
} finally {
StrictMode.setThreadPolicy(oldPolicy);
}
}
String requiredAbi = (abiOverride != null) ? abiOverride : app.info.primaryCpuAbi;
if (requiredAbi == null) {
requiredAbi = Build.SUPPORTED_ABIS[0];
}
String instructionSet = null;
if (app.info.primaryCpuAbi != null) {
instructionSet = VMRuntime.getInstructionSet(app.info.primaryCpuAbi);
}
app.gids = gids;
app.setRequiredAbi(requiredAbi);
app.instructionSet = instructionSet;
// If instructionSet is non-null, this indicates that the system_server is spawning a
// process with an ISA that may be different from its own. System (kernel and hardware)
// compatililty for these features is checked in the decideTaggingLevel in the
// system_server process (not the child process). As both MTE and TBI are only supported
// in aarch64, we can simply ensure that the new process is also aarch64. This prevents
// the mismatch where a 64-bit system server spawns a 32-bit child that thinks it should
// enable some tagging variant. Theoretically, a 32-bit system server could exist that
// spawns 64-bit processes, in which case the new process won't get any tagging. This is
// fine as we haven't seen this configuration in practice, and we can reasonable assume
// that if tagging is desired, the system server will be 64-bit.
if (instructionSet == null || instructionSet.equals("arm64")) {
runtimeFlags |= decideTaggingLevel(app);
}
if (enableNativeHeapZeroInit(app)) {
runtimeFlags |= Zygote.NATIVE_HEAP_ZERO_INIT;
}
// the per-user SELinux context must be set
//必须设置每个用户的 SELinux 上下文
if (TextUtils.isEmpty(app.info.seInfoUser)) {
Slog.wtf(ActivityManagerService.TAG, "SELinux tag not defined",
new IllegalStateException("SELinux tag not defined for "
+ app.info.packageName + " (uid " + app.uid + ")"));
}
final String seInfo = app.info.seInfo
+ (TextUtils.isEmpty(app.info.seInfoUser) ? "" : app.info.seInfoUser);
// Start the process. It will either succeed and return a result containing
// the PID of the new process, or else throw a RuntimeException.
// 启动进程，要么成功并返回一个包含新进程PID的结果，要么抛出一个RuntimeException
final String entryPoint = "android.app.ActivityThread";
return startProcessLocked(hostingRecord, entryPoint, app, uid, gids,
runtimeFlags, zygotePolicyFlags, mountExternal, seInfo, requiredAbi,
instructionSet, invokeWith, startTime);//关键是看这里调用
} catch (RuntimeException e) {
Slog.e(ActivityManagerService.TAG, "Failure starting process " + app.processName, e);
// Something went very wrong while trying to start this process; one
// common case is when the package is frozen due to an active
// upgrade. To recover, clean up any active bookkeeping related to
// starting this process. (We already invoked this method once when
// the package was initially frozen through KILL_APPLICATION_MSG, so
// it doesn't hurt to use it again.)
mService.forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid),
false, false, true, false, false, app.userId, "start failure");
return false;
}
}
@GuardedBy("mService")
boolean startProcessLocked(HostingRecord hostingRecord, String entryPoint, ProcessRecord app,
int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags, int mountExternal,
String seInfo, String requiredAbi, String instructionSet, String invokeWith,
long startTime) {
app.pendingStart = true;
app.killedByAm = false;
app.removed = false;
app.killed = false;
if (app.startSeq != 0) {
Slog.wtf(TAG, "startProcessLocked processName:" + app.processName
+ " with non-zero startSeq:" + app.startSeq);
}
if (app.pid != 0) {
Slog.wtf(TAG, "startProcessLocked processName:" + app.processName
+ " with non-zero pid:" + app.pid);
}
app.mDisabledCompatChanges = null;
if (mPlatformCompat != null) {
app.mDisabledCompatChanges = mPlatformCompat.getDisabledChanges(app.info);
}
final long startSeq = app.startSeq = ++mProcStartSeqCounter;
app.setStartParams(uid, hostingRecord, seInfo, startTime);
app.setUsingWrapper(invokeWith != null
|| Zygote.getWrapProperty(app.processName) != null);
mPendingStarts.put(startSeq, app);//把新建的ProcessRecord 添加进 mPendingStarts 中
if (mService.mConstants.FLAG_PROCESS_START_ASYNC) {//异步启动?走不进这里
if (DEBUG_PROCESSES) Slog.i(TAG_PROCESSES,
"Posting procStart msg for " + app.toShortString());
mService.mProcStartHandler.post(() -> handleProcessStart(
app, entryPoint, gids, runtimeFlags, zygotePolicyFlags, mountExternal,
requiredAbi, instructionSet, invokeWith, startSeq));
return true;
} else {
try {
final Process.ProcessStartResult startResult = startProcess(hostingRecord,
entryPoint, app,
uid, gids, runtimeFlags, zygotePolicyFlags, mountExternal, seInfo,
requiredAbi, instructionSet, invokeWith, startTime);//关键点1
handleProcessStartedLocked(app, startResult.pid, startResult.usingWrapper,
startSeq, false);//关键点2
//新的的应用程序进程创建成功之后，当前进程就会得到一个大于0的进程ID，保存在变量pid中，
//在该方法中以变量pid为关键字将参数app所指向的一个ProcessRecord对象保存在AMS类的成员变量mPidsSelfLocked中，
//并向AMS所运行在的线程消息队列中发送一个类型为PROC_START_TIMEOUT_MSG的消息，指定在PROC_START_TIMEOUT时间后执行。
//新的应用程序进程须在PROC_START_TIMEOUT时间内完成启动工作，并向AMS发送一个启动完成的通知，
//以便AMS可以在该进程中启动Activity组件。
} catch (RuntimeException e) {
Slog.e(ActivityManagerService.TAG, "Failure starting process "
+ app.processName, e);
app.pendingStart = false;
mService.forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid),
false, false, true, false, false, app.userId, "start failure");
}
return app.pid > 0;
}
}
private Process.ProcessStartResult startProcess(HostingRecord hostingRecord, String entryPoint,
ProcessRecord app, int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags,
int mountExternal, String seInfo, String requiredAbi, String instructionSet,
String invokeWith, long startTime) {
try {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Start proc: " +
app.processName);
checkSlow(startTime, "startProcess: asking zygote to start proc");
final boolean isTopApp = hostingRecord.isTopApp();
if (isTopApp) {
// Use has-foreground-activities as a temporary hint so the current scheduling
// group won't be lost when the process is attaching. The actual state will be
// refreshed when computing oom-adj.
app.setHasForegroundActivities(true);
}
Map<String, Pair<String, Long>> pkgDataInfoMap;
Map<String, Pair<String, Long>> whitelistedAppDataInfoMap;
boolean bindMountAppStorageDirs = false;
boolean bindMountAppsData = mAppDataIsolationEnabled
&& (UserHandle.isApp(app.uid) || UserHandle.isIsolated(app.uid))
&& mPlatformCompat.isChangeEnabled(APP_DATA_DIRECTORY_ISOLATION, app.info);
// Get all packages belongs to the same shared uid. sharedPackages is empty array
// if it doesn't have shared uid.
final PackageManagerInternal pmInt = mService.getPackageManagerInternalLocked();
final String[] sharedPackages = pmInt.getSharedUserPackagesForPackage(
app.info.packageName, app.userId);
final String[] targetPackagesList = sharedPackages.length == 0
? new String[]{app.info.packageName} : sharedPackages;
pkgDataInfoMap = getPackageAppDataInfoMap(pmInt, targetPackagesList, uid);
if (pkgDataInfoMap == null) {
// TODO(b/152760674): Handle inode == 0 case properly, now we just give it a
// tmp free pass.
bindMountAppsData = false;
}
// Remove all packages in pkgDataInfoMap from mAppDataIsolationWhitelistedApps, so
// it won't be mounted twice.
final Set<String> whitelistedApps = new ArraySet<>(mAppDataIsolationWhitelistedApps);
for (String pkg : targetPackagesList) {
whitelistedApps.remove(pkg);
}
whitelistedAppDataInfoMap = getPackageAppDataInfoMap(pmInt,
whitelistedApps.toArray(new String[0]), uid);
if (whitelistedAppDataInfoMap == null) {
// TODO(b/152760674): Handle inode == 0 case properly, now we just give it a
// tmp free pass.
bindMountAppsData = false;
}
int userId = UserHandle.getUserId(uid);
StorageManagerInternal storageManagerInternal = LocalServices.getService(
StorageManagerInternal.class);
if (needsStorageDataIsolation(storageManagerInternal, app)) {
bindMountAppStorageDirs = true;
if (pkgDataInfoMap == null ||
!storageManagerInternal.prepareStorageDirs(userId, pkgDataInfoMap.keySet(),
app.processName)) {
// Cannot prepare Android/app and Android/obb directory or inode == 0,
// so we won't mount it in zygote, but resume the mount after unlocking device.
app.bindMountPending = true;
bindMountAppStorageDirs = false;
}
}
// If it's an isolated process, it should not even mount its own app data directories,
// since it has no access to them anyway.
if (app.isolated) {
pkgDataInfoMap = null;
whitelistedAppDataInfoMap = null;
}
//根据hostingRecord中的hostingType标志，选择对应的进程启动分支，默认的hostingType为REGULAR_ZYGOTE，
//故调用Process::start()函数把进程启动请求传递到Zygote中。
final Process.ProcessStartResult startResult;
if (hostingRecord.usesWebviewZygote()) {//不走
startResult = startWebView(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, null, app.info.packageName, app.mDisabledCompatChanges,
new String[]{PROC_START_SEQ_IDENT + app.startSeq});
} else if (hostingRecord.usesAppZygote()) {//不走
final AppZygote appZygote = createAppZygoteForProcessIfNeeded(app);
// We can't isolate app data and storage data as parent zygote already did that.
startResult = appZygote.getProcess().start(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, null, app.info.packageName,
/*zygotePolicyFlags=*/ ZYGOTE_POLICY_FLAG_EMPTY, isTopApp,
app.mDisabledCompatChanges, pkgDataInfoMap, whitelistedAppDataInfoMap,
false, false,
new String[]{PROC_START_SEQ_IDENT + app.startSeq});
} else {//走这里
startResult = Process.start(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, invokeWith, app.info.packageName, zygotePolicyFlags,
isTopApp, app.mDisabledCompatChanges, pkgDataInfoMap,
whitelistedAppDataInfoMap, bindMountAppsData, bindMountAppStorageDirs,
new String[]{PROC_START_SEQ_IDENT + app.startSeq});
}
checkSlow(startTime, "startProcess: returned from zygote!");
return startResult;
} finally {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
}
Process.java core\java\android\os
Tools for managing OS processes.
管理系统进程的工具类！直接调用
public static ProcessStartResult start(@NonNull final String processClass,
@Nullable final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags,
int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
whitelistedDataInfoMap,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
return ZYGOTE_PROCESS.start(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, packageName,
zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, whitelistedDataInfoMap, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
}
ZygoteProcess.java core\java\android\os
保持与 zygote 进程的通信状态。 此类负责向zygote打开的套接字并代表zygote启动进程
ZygoteProcess#startViaZygote：将要创建的应用程序进程的启动参数保存在argsForZygote中，调用openZygoteSocketIfNeeded函数打开与Zygote进程的Socket连接，返回ZygoteState实例，然后把该实例同argsForZygote作为参数传入到zygoteSendArgsAndGetResult；在应用程序进程的启动参数列表中，有一个重要的参数"--runtime-init"，它表示要在新创建的应用程序进程中初始化运行时库，以及启动一个Binder线程池。
public final Process.ProcessStartResult start(@NonNull final String processClass,
final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
allowlistedDataInfoList,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
// TODO (chriswailes): Is there a better place to check this value?
if (fetchUsapPoolEnabledPropWithMinInterval()) {
informZygotesOfUsapPoolStatus();
}
try {
return startViaZygote(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, /*startChildZygote=*/ false,
packageName, zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, allowlistedDataInfoList, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
} catch (ZygoteStartFailedEx ex) {
Log.e(LOG_TAG,
"Starting VM process through Zygote failed");
throw new RuntimeException(
"Starting VM process through Zygote failed", ex);
}
}
private Process.ProcessStartResult startViaZygote(@NonNull final String processClass,
@Nullable final String niceName,
final int uid, final int gid,
@Nullable final int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
boolean startChildZygote,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
allowlistedDataInfoList,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] extraArgs)
throws ZygoteStartFailedEx {
ArrayList<String> argsForZygote = new ArrayList<>();
// --runtime-args, --setuid=, --setgid=,
// and --setgroups= must go first
argsForZygote.add("--runtime-args");
argsForZygote.add("--setuid=" + uid);
argsForZygote.add("--setgid=" + gid);
argsForZygote.add("--runtime-flags=" + runtimeFlags);
if (mountExternal == Zygote.MOUNT_EXTERNAL_DEFAULT) {
argsForZygote.add("--mount-external-default");
} else if (mountExternal == Zygote.MOUNT_EXTERNAL_INSTALLER) {
argsForZygote.add("--mount-external-installer");
} else if (mountExternal == Zygote.MOUNT_EXTERNAL_PASS_THROUGH) {
argsForZygote.add("--mount-external-pass-through");
} else if (mountExternal == Zygote.MOUNT_EXTERNAL_ANDROID_WRITABLE) {
argsForZygote.add("--mount-external-android-writable");
}
argsForZygote.add("--target-sdk-version=" + targetSdkVersion);
// --setgroups is a comma-separated list
if (gids != null && gids.length > 0) {
final StringBuilder sb = new StringBuilder();
sb.append("--setgroups=");
final int sz = gids.length;
for (int i = 0; i < sz; i++) {
if (i != 0) {
sb.append(',');
}
sb.append(gids[i]);
}
argsForZygote.add(sb.toString());
}
if (niceName != null) {
argsForZygote.add("--nice-name=" + niceName);
}
if (seInfo != null) {
argsForZygote.add("--seinfo=" + seInfo);
}
if (instructionSet != null) {
argsForZygote.add("--instruction-set=" + instructionSet);
}
if (appDataDir != null) {
argsForZygote.add("--app-data-dir=" + appDataDir);
}
if (invokeWith != null) {
argsForZygote.add("--invoke-with");
argsForZygote.add(invokeWith);
}
if (startChildZygote) {
argsForZygote.add("--start-child-zygote");
}
if (packageName != null) {
argsForZygote.add("--package-name=" + packageName);
}
if (isTopApp) {
argsForZygote.add(Zygote.START_AS_TOP_APP_ARG);
}
if (pkgDataInfoMap != null && pkgDataInfoMap.size() > 0) {
StringBuilder sb = new StringBuilder();
sb.append(Zygote.PKG_DATA_INFO_MAP);
sb.append("=");
boolean started = false;
for (Map.Entry<String, Pair<String, Long>> entry : pkgDataInfoMap.entrySet()) {
if (started) {
sb.append(',');
}
started = true;
sb.append(entry.getKey());
sb.append(',');
sb.append(entry.getValue().first);
sb.append(',');
sb.append(entry.getValue().second);
}
argsForZygote.add(sb.toString());
}
if (allowlistedDataInfoList != null && allowlistedDataInfoList.size() > 0) {
StringBuilder sb = new StringBuilder();
sb.append(Zygote.ALLOWLISTED_DATA_INFO_MAP);
sb.append("=");
boolean started = false;
for (Map.Entry<String, Pair<String, Long>> entry : allowlistedDataInfoList.entrySet()) {
if (started) {
sb.append(',');
}
started = true;
sb.append(entry.getKey());
sb.append(',');
sb.append(entry.getValue().first);
sb.append(',');
sb.append(entry.getValue().second);
}
argsForZygote.add(sb.toString());
}
if (bindMountAppStorageDirs) {
argsForZygote.add(Zygote.BIND_MOUNT_APP_STORAGE_DIRS);
}
if (bindMountAppsData) {
argsForZygote.add(Zygote.BIND_MOUNT_APP_DATA_DIRS);
}
if (disabledCompatChanges != null && disabledCompatChanges.length > 0) {
StringBuilder sb = new StringBuilder();
sb.append("--disabled-compat-changes=");
int sz = disabledCompatChanges.length;
for (int i = 0; i < sz; i++) {
if (i != 0) {
sb.append(',');
}
sb.append(disabledCompatChanges[i]);
}
argsForZygote.add(sb.toString());
}
argsForZygote.add(processClass);
if (extraArgs != null) {
Collections.addAll(argsForZygote, extraArgs);
}
synchronized(mLock) {
// The USAP pool can not be used if the application will not use the systems graphics
// driver. If that driver is requested use the Zygote application start path.
return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi),
zygotePolicyFlags,
argsForZygote);
}
}
private Process.ProcessStartResult zygoteSendArgsAndGetResult(
ZygoteState zygoteState, int zygotePolicyFlags, @NonNull ArrayList<String> args)
throws ZygoteStartFailedEx {
// Throw early if any of the arguments are malformed. This means we can
// avoid writing a partial response to the zygote.
for (String arg : args) {
// Making two indexOf calls here is faster than running a manually fused loop due
// to the fact that indexOf is an optimized intrinsic.
if (arg.indexOf('\n') >= 0) {
throw new ZygoteStartFailedEx("Embedded newlines not allowed");
} else if (arg.indexOf('\r') >= 0) {
throw new ZygoteStartFailedEx("Embedded carriage returns not allowed");
}
}
/*
* See com.android.internal.os.ZygoteArguments.parseArgs()
* Presently the wire format to the zygote process is:
* a) a count of arguments (argc, in essence)
* b) a number of newline-separated argument strings equal to count
*
* After the zygote process reads these it will write the pid of
* the child or -1 on failure, followed by boolean to
* indicate whether a wrapper process was used.
*/
String msgStr = args.size() + "\n" + String.join("\n", args) + "\n";
if (shouldAttemptUsapLaunch(zygotePolicyFlags, args)) {
try {
return attemptUsapSendArgsAndGetResult(zygoteState, msgStr);
} catch (IOException ex) {
// If there was an IOException using the USAP pool we will log the error and
// attempt to start the process through the Zygote.
Log.e(LOG_TAG, "IO Exception while communicating with USAP pool - "
+ ex.getMessage());
}
}
return attemptZygoteSendArgsAndGetResult(zygoteState, msgStr);
}
private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(
ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {
try {
final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;
final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;
zygoteWriter.write(msgStr);
zygoteWriter.flush();
// Always read the entire result from the input stream to avoid leaving
// bytes in the stream for future process starts to accidentally stumble
// upon.
Process.ProcessStartResult result = new Process.ProcessStartResult();
result.pid = zygoteInputStream.readInt();
result.usingWrapper = zygoteInputStream.readBoolean();
if (result.pid < 0) {
throw new ZygoteStartFailedEx("fork() failed");
}
return result;
} catch (IOException ex) {
zygoteState.close();
Log.e(LOG_TAG, "IO Exception while communicating with Zygote - "
+ ex.toString());
throw new ZygoteStartFailedEx(ex);
}
}
