Android SurfaceFlinger之SurfaceFlinger启动过程
http://blog.csdn.net/ieearth/article/details/61202963
SurfaceFlinger的启动脚本surfaceflinger.rc内容如下：
service surfaceflinger /system/bin/surfaceflinger
class core
user system
group graphics drmrpc readproc
onrestart restart zygote
writepid /dev/stune/foreground/tasks其main函数在frameworks/native/services/surfaceflinger/main_surfaceflinger.cpp，如下：
int main(int, char**) {
signal(SIGPIPE, SIG_IGN);
// When SF is launched in its own process, limit the number of
// binder threads to 4.
ProcessState::self()->setThreadPoolMaxThreadCount(4);
// start the thread pool
sp<ProcessState> ps(ProcessState::self());
ps->startThreadPool();
// instantiate surfaceflinger
sp<SurfaceFlinger> flinger = new SurfaceFlinger();
setpriority(PRIO_PROCESS, 0, PRIORITY_URGENT_DISPLAY);
set_sched_policy(0, SP_FOREGROUND);
#ifdef ENABLE_CPUSETS
// Put most SurfaceFlinger threads in the system-background cpuset
// Keeps us from unnecessarily using big cores
// Do this after the binder thread pool init
set_cpuset_policy(0, SP_SYSTEM);
#endif
// initialize before clients can connect
flinger->init();
// publish surface flinger
sp<IServiceManager> sm(defaultServiceManager());
sm->addService(String16(SurfaceFlinger::getServiceName()), flinger, false);
// publish GpuService
sp<GpuService> gpuservice = new GpuService();
sm->addService(String16(GpuService::SERVICE_NAME), gpuservice, false);
struct sched_param param = {0};
param.sched_priority = 2;
if (sched_setscheduler(0, SCHED_FIFO, ¶m) != 0) {
ALOGE("Couldn't set SCHED_FIFO");
}
// run surface flinger in this thread
flinger->run();
return 0;
}1、SurfaceFlinger首先忽略了SIGPIPE信号，为什么要这么做呢？因为在SurfaceFlinger的Client-Server模型中，或者说IPC机制中，很可能会触发SIGPIPE信号，而这个信号的默认动作是终止进程，并不是我们想要的行为，所以主动对SIGPIPE信号进行处理。
2、接着，开启线程池，不过限制了线程的最大数量为4个，如果线程过多，可能会影响程序性能。
3、随后，创建SurfaceFlinger对象，在其构造函数中，主要是一些成员变量的初始化工作，同时还有一个高逼格的DDMS配置，即Dalvik Debug Monitor Service，是一个调试神器。如果配置了DDMS，就会dlopen libsurfaceflinger_ddmconnection.so，并dlsym其中的DdmConnection_start，最后建立SurfaceFlinger与DDMS的连接。
class SurfaceFlinger : public BnSurfaceComposer,
private IBinder::DeathRecipient,
private HWComposer::EventHandler
SurfaceFlinger::SurfaceFlinger()
: BnSurfaceComposer(),
mTransactionFlags(0),
mTransactionPending(false),
mAnimTransactionPending(false),
mLayersRemoved(false),
mRepaintEverything(0),
mRenderEngine(NULL),
mBootTime(systemTime()),
mBuiltinDisplays(),
mVisibleRegionsDirty(false),
mGeometryInvalid(false),
mAnimCompositionPending(false),
mDebugRegion(0),
mDebugDDMS(0),
mDebugDisableHWC(0),
mDebugDisableTransformHint(0),
mDebugInSwapBuffers(0),
mLastSwapBufferTime(0),
mDebugInTransaction(0),
mLastTransactionTime(0),
mBootFinished(false),
mForceFullDamage(false),
mPrimaryDispSync("PrimaryDispSync"),
mPrimaryHWVsyncEnabled(false),
mHWVsyncAvailable(false),
mHasColorMatrix(false),
mHasPoweredOff(false),
mFrameBuckets(),
mTotalTime(0),
mLastSwapTime(0)
{
ALOGI("SurfaceFlinger is starting");
// debugging stuff...
char value[PROPERTY_VALUE_MAX];
property_get("ro.bq.gpu_to_cpu_unsupported", value, "0");
mGpuToCpuSupported = !atoi(value);
property_get("debug.sf.showupdates", value, "0");
mDebugRegion = atoi(value);
property_get("debug.sf.ddms", value, "0");
mDebugDDMS = atoi(value);
if (mDebugDDMS) {
if (!startDdmConnection()) {
// start failed, and DDMS debugging not enabled
mDebugDDMS = 0;
}
}
ALOGI_IF(mDebugRegion, "showupdates enabled");
ALOGI_IF(mDebugDDMS, "DDMS debugging enabled");
property_get("debug.sf.disable_backpressure", value, "0");
mPropagateBackpressure = !atoi(value);
ALOGI_IF(!mPropagateBackpressure, "Disabling backpressure propagation");
property_get("debug.sf.disable_hwc_vds", value, "0");
mUseHwcVirtualDisplays = !atoi(value);
ALOGI_IF(!mUseHwcVirtualDisplays, "Disabling HWC virtual displays");
}因为这里的SurfaceFlinger对象是一个StrongPointer，所以首先会走到RefBase的onFirstRef，这里就做了一件事情，MessageQueue初始化，保存SurfaceFlinger，并创建了消息队列所需的Looper和Handler。
void SurfaceFlinger::onFirstRef()
{
mEventQueue.init(this);
}
void MessageQueue::init(const sp<SurfaceFlinger>& flinger)
{
mFlinger = flinger;
mLooper = new Looper(true);
mHandler = new Handler(*this);
}4、SurfaceFlinger实例化后，设置进程优先级和事务处理策略。
5、然后，进入如下的SurfaceFlinger::init，主要是EGL配置、event线程启动、硬件composer初始化等，而且著名的VSync也在这里出现了。
void SurfaceFlinger::init() {
ALOGI( "SurfaceFlinger's main thread ready to run. "
"Initializing graphics H/W...");
{ // Autolock scope
Mutex::Autolock _l(mStateLock);
// initialize EGL for the default display
mEGLDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
eglInitialize(mEGLDisplay, NULL, NULL);
// start the EventThread
sp<VSyncSource> vsyncSrc = new DispSyncSource(&mPrimaryDispSync,
vsyncPhaseOffsetNs, true, "app");
mEventThread = new EventThread(vsyncSrc, *this);
sp<VSyncSource> sfVsyncSrc = new DispSyncSource(&mPrimaryDispSync,
sfVsyncPhaseOffsetNs, true, "sf");
mSFEventThread = new EventThread(sfVsyncSrc, *this);
mEventQueue.setEventThread(mSFEventThread);
// set SFEventThread to SCHED_FIFO to minimize jitter
struct sched_param param = {0};
param.sched_priority = 2;
if (sched_setscheduler(mSFEventThread->getTid(), SCHED_FIFO, ¶m) != 0) {
ALOGE("Couldn't set SCHED_FIFO for SFEventThread");
}
// Get a RenderEngine for the given display / config (can't fail)
mRenderEngine = RenderEngine::create(mEGLDisplay,
HAL_PIXEL_FORMAT_RGBA_8888);
}
// Drop the state lock while we initialize the hardware composer. We drop
// the lock because on creation, it will call back into SurfaceFlinger to
// initialize the primary display.
mHwc = new HWComposer(this);
mHwc->setEventHandler(static_cast<HWComposer::EventHandler*>(this));
Mutex::Autolock _l(mStateLock);
// retrieve the EGL context that was selected/created
mEGLContext = mRenderEngine->getEGLContext();
LOG_ALWAYS_FATAL_IF(mEGLContext == EGL_NO_CONTEXT,
"couldn't create EGLContext");
// make the GLContext current so that we can create textures when creating
// Layers (which may happens before we render something)
getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
mEventControlThread = new EventControlThread(this);
mEventControlThread->run("EventControl", PRIORITY_URGENT_DISPLAY);
// initialize our drawing state
mDrawingState = mCurrentState;
// set initial conditions (e.g. unblank default device)
initializeDisplays();
mRenderEngine->primeCache();
// start boot animation
startBootAnim();
ALOGV("Done initializing");
}6、在Android系统中有一个ServiceManager，专门用来管理所有的服务，而SurfaceFlinger不是由ServiceManager启动的，因此需要向ServiceManager注册SurfaceFlinger，同时还注册了GpuService。
7、最后通过SurfaceFlinger::run，进入消息循环，SurfaceFlinger启动成功，开始工作。
void SurfaceFlinger::run() {
do {
waitForEvent();
} while (true);
}
