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下面是android启动到界面显示流程图
kernel/init/main.c
asmlinkage void __init start_kernel(void)//这是kernel的入口，head-common.S汇编代码会连接过来。
{
......
ftrace_init();
/* Do the rest non-__init'ed, we're now alive */
rest_init();
}
static noinline void __init_refok rest_init(void)
{
.......
/*
* We need to spawn init first so that it obtains pid 1, however
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
.......................
}
static int __init kernel_init(void * unused)
{
.........
if (!ramdisk_execute_command)
<span style="color:#ff0000;">ramdisk_execute_command = "/init"</span>;//指定init文件的位置
if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
}
/*
* Ok, we have completed the initial bootup, and
* we're essentially up and running. Get rid of the
* initmem segments and start the user-mode stuff..
*/
init_post();
return 0;
}
static noinline int init_post(void)
{
/* need to finish all async __init code before freeing the memory */
async_synchronize_full();
free_initmem();
mark_rodata_ro();
system_state = SYSTEM_RUNNING;
numa_default_policy();
current->signal->flags |= SIGNAL_UNKILLABLE;
if (ramdisk_execute_command) {
run_init_process(ramdisk_execute_command);//调用run_init_process函数，init进程跑起来
printk(KERN_WARNING "Failed to execute %s\n",
ramdisk_execute_command);
}
...........
}
[init.rc]
service servicemanager /system/bin/servicemanager//看到吧，
class core
user system
group system
critical
onrestart restart healthd
onrestart restart zygote
onrestart restart media
onrestart restart surfaceflinger
onrestart restart drm
frameworks/native/cmds/servicemanager/service_manager.c
//下面是进程代码，他负责管理本地系统服务和java系统服务，为下面本地系统服务，java系统服务的注册提供基础。
[c]
void *do_find_service(struct binder_state *bs, uint16_t *s, unsigned len, unsigned uid)
{
}
int do_add_service(struct binder_state *bs,
uint16_t *s, unsigned len,
void *ptr, unsigned uid, int allow_isolated)
{
}
int main(int argc, char **argv)
{
struct binder_state *bs;
void *svcmgr = BINDER_SERVICE_MANAGER;
bs = binder_open(128*1024);
if (binder_become_context_manager(bs)) {
ALOGE("cannot become context manager (%s)\n", strerror(errno));
return -1;
}
svcmgr_handle = svcmgr;
binder_loop(bs, svcmgr_handler);
return 0;
}service media /system/bin/mediaserver
class main
user media
group audio camera inet net_bt net_bt_admin net_bw_acct drmrpc mediadrm qcom_diag
ioprio rt 4
frameworks/av/media/mediaserver/main_mediaserver.cpp
//启动一系列本地系统服务
</pre><pre>
[cpp]
int main(int argc, char** argv)
{
........
AudioFlinger::instantiate();
MediaPlayerService::instantiate();
CameraService::instantiate();
#ifdef QCOM_LISTEN_FEATURE_ENABLE
ALOGI("ListenService instantiated");
ListenService::instantiate();
#endif
AudioPolicyService::instantiate();
#ifdef RESOURCE_MANAGER
ALOGI(" ResourceManagerService instantiated");
ResourceManagerService::instantiate();
#endif
registerExtensions();
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
}
}
service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server//Zygote是通过app_process进程启动的，注意：zygote是java代码进程
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
onrestart write /sys/power/state on
onrestart restart media
onrestart restart netd
frameworks/base/cmds/app_process/app_main.cpp
[cpp]
int main(int argc, char* const argv[])
{
<span style="color:#ff0000;">//建立android runtime,然后启动Zygote进程</span>
runtime.start("com.android.internal.os.ZygoteInit",
startSystemServer ? "start-system-server" : "");
｝
frameworks/base/core/jni/AndroidRuntime.cpp
runtime里建立虚拟机，然后启动Zygote进程
void AndroidRuntime::start(const char* className, const char* options)
{
<span style="color:#ff0000;">//runtime建立虚拟机,</span>
/* start the virtual machine */
JNIEnv* env;
if (startVm(&mJavaVM, &env) != 0) {
return;
}
onVmCreated(env);
//启动java进程，上面讲到的Zygote
/*
* Start VM. This thread becomes the main thread of the VM, and will
* not return until the VM exits.
*/
char* slashClassName = toSlashClassName(className);
jclass startClass = env->FindClass(slashClassName);
if (startClass == NULL) {
ALOGE("JavaVM unable to locate class '%s'\n", slashClassName);
/* keep going */
} else {
jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
"([Ljava/lang/String;)V");
if (startMeth == NULL) {
ALOGE("JavaVM unable to find main() in '%s'\n", className);
/* keep going */
} else {
env->CallStaticVoidMethod(startClass, startMeth, strArray);
#if 0
if (env->ExceptionCheck())
threadExitUncaughtException(env);
#endif
}
}frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
public static void main(String argv[]) {
try {
// Start profiling the zygote initialization.
SamplingProfilerIntegration.start();
<span style="color:#ff0000;"> registerZygoteSocket();//注册listner接口</span>
EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_START,
SystemClock.uptimeMillis());
preload();
EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END,
SystemClock.uptimeMillis());
// 20131109 add for bootprof begin
addBootEvent(new String("Zygote:Preload Start"));
// 20131109 add for bootprof end
// Finish profiling the zygote initialization.
SamplingProfilerIntegration.writeZygoteSnapshot();
// Do an initial gc to clean up after startup
gc();
// Disable tracing so that forked processes do not inherit stale tracing tags from
// Zygote.
Trace.setTracingEnabled(false);
// If requested, start system server directly from Zygote
if (argv.length != 2) {
throw new RuntimeException(argv[0] + USAGE_STRING);
}
// 20131109 add for bootprof begin
addBootEvent(new String("Zygote:Preload End"));
//20131109 add for bootprof end
if (argv[1].equals("start-system-server")) {
startSystemServer();//启动system server
} else if (!argv[1].equals("")) {
throw new RuntimeException(argv[0] + USAGE_STRING);
}
Log.i(TAG, "Accepting command socket connections");
runSelectLoop();
closeServerSocket();
} catch (MethodAndArgsCaller caller) {
caller.run();
} catch (RuntimeException ex) {
Log.e(TAG, "Zygote died with exception", ex);
closeServerSocket();
throw ex;
}
}注：Zygote启动system server进程，还注册Scoket通道，接收来自ActivityManagerService的请求，Fork应用程序
frameworks/base/services/java/com/android/server/SystemServer.java
//启动一系列java系统服务
public class SystemServer {
private static final String TAG = "SystemServer";
.......
/**
* Called to initialize native system services.
*/
private static native void nativeInit();
public static void main(String[] args) {
.......
// Initialize native services.
nativeInit();
// This used to be its own separate thread, but now it is
// just the loop we run on the main thread.
ServerThread thr = new ServerThread();
thr.initAndLoop();
}
}
class ServerThread {
private static final String TAG = "SystemServer";
private static final String ENCRYPTING_STATE = "trigger_restart_min_framework";
private static final String ENCRYPTED_STATE = "1";
ContentResolver mContentResolver;
void reportWtf(String msg, Throwable e) {
Slog.w(TAG, "***********************************************");
Log.wtf(TAG, "BOOT FAILURE " + msg, e);
}
public void initAndLoop() {
.....
Slog.i(TAG, "Content Manager");
contentService = ContentService.main(context,
factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);
Slog.i(TAG, "System Content Providers");
ActivityManagerService.installSystemProviders();
Slog.i(TAG, "Lights Service");
lights = new LightsService(context);
Slog.i(TAG, "Battery Service");
battery = new BatteryService(context, lights);
ServiceManager.addService("battery", battery);
Slog.i(TAG, "Vibrator Service");
vibrator = new VibratorService(context);
ServiceManager.addService("vibrator", vibrator);
Slog.i(TAG, "Consumer IR Service");
consumerIr = new ConsumerIrService(context);
ServiceManager.addService(Context.CONSUMER_IR_SERVICE, consumerIr);
.......
}
}
frameworks/base/services/java/com/android/server/am/ActivityManagerService.java
system server启动java系统服务后，会发出systemRready的通知。
ActivityManagerService的SystemReady函数回调
发出UserSwitch的广播启动Home
public void systemReady(final Runnable goingCallback) {
synchronized(this) {
if (mSystemReady) {
if (goingCallback != null) goingCallback.run();
return;
}
mStackSupervisor.resumeTopActivitiesLocked();
sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);
}
}
@Override
public boolean switchUser(final int userId) {
boolean homeInFront = mStackSupervisor.switchUserLocked(userId, uss);
if (homeInFront) {
<span style="color:#ff0000;">startHomeActivityLocked(userId);</span>
} else {
mStackSupervisor.resumeTopActivitiesLocked();
}
｝
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原文地址：http://blog.csdn.net/hovan/article/details/42172481
