1. SurfaceFlinger程序入口

/frameworks/native/services/surfaceflinger/main_surfaceflinger.cpp

1int main(int, char**) {
2    signal(SIGPIPE, SIG_IGN);
3 
4    hardware::configureRpcThreadpool(1 /* maxThreads */,
5            false /* callerWillJoin */);
6 
7    startGraphicsAllocatorService();
8 
9    // When SF is launched in its own process, limit the number of
10    // binder threads to 4.
11    ProcessState::self()->setThreadPoolMaxThreadCount(4);
12 
13    // Set uclamp.min setting on all threads, maybe an overkill but we want
14    // to cover important threads like RenderEngine.
15    if (SurfaceFlinger::setSchedAttr(true) != NO_ERROR) {
16        ALOGW("Couldn't set uclamp.min: %s\n", strerror(errno));
17    }
18 
19    // The binder threadpool we start will inherit sched policy and priority
20    // of (this) creating thread. We want the binder thread pool to have
21    // SCHED_FIFO policy and priority 1 (lowest RT priority)
22    // Once the pool is created we reset this thread's priority back to
23    // original.
24    int newPriority = 0;
25    int origPolicy = sched_getscheduler(0);
26    struct sched_param origSchedParam;
27 
28    int errorInPriorityModification = sched_getparam(0, &origSchedParam);
29    if (errorInPriorityModification == 0) {
30        int policy = SCHED_FIFO;
31        newPriority = sched_get_priority_min(policy);
32 
33        struct sched_param param;
34        param.sched_priority = newPriority;
35 
36        errorInPriorityModification = sched_setscheduler(0, policy, &param);
37    }
38 
39    // start the thread pool
40    sp<ProcessState> ps(ProcessState::self());
41    ps->startThreadPool();
42 
43    // Reset current thread's policy and priority
44    if (errorInPriorityModification == 0) {
45        errorInPriorityModification = sched_setscheduler(0, origPolicy, &origSchedParam);
46    } else {
47        ALOGE("Failed to set SurfaceFlinger binder threadpool priority to SCHED_FIFO");
48    }
49 
50    // instantiate surfaceflinger
51    sp<SurfaceFlinger> flinger = surfaceflinger::createSurfaceFlinger();
52 
53    // Set the minimum policy of surfaceflinger node to be SCHED_FIFO.
54    // So any thread with policy/priority lower than {SCHED_FIFO, 1}, will run
55    // at least with SCHED_FIFO policy and priority 1.
56    if (errorInPriorityModification == 0) {
57        flinger->setMinSchedulerPolicy(SCHED_FIFO, newPriority);
58    }
59 
60    setpriority(PRIO_PROCESS, 0, PRIORITY_URGENT_DISPLAY);
61 
62    set_sched_policy(0, SP_FOREGROUND);
63 
64    // Put most SurfaceFlinger threads in the system-background cpuset
65    // Keeps us from unnecessarily using big cores
66    // Do this after the binder thread pool init
67    if (cpusets_enabled()) set_cpuset_policy(0, SP_SYSTEM);
68 
69    // initialize before clients can connect
70    flinger->init();
71 
72    // publish surface flinger
73    sp<IServiceManager> sm(defaultServiceManager());
74    sm->addService(String16(SurfaceFlinger::getServiceName()), flinger, false,
75                   IServiceManager::DUMP_FLAG_PRIORITY_CRITICAL | IServiceManager::DUMP_FLAG_PROTO);
76 
77    startDisplayService(); // dependency on SF getting registered above
78 
79    if (SurfaceFlinger::setSchedFifo(true) != NO_ERROR) {
80        ALOGW("Couldn't set to SCHED_FIFO: %s", strerror(errno));
81    }
82 
83    // run surface flinger in this thread
84    flinger->run();/ Use StartPropertySetThread instead.
85}
86 
87 
88void SurfaceFlinger::onFirstRef() {
89    // std::unique_ptr<MessageQueue> mEventQueue;
90    mEventQueue->init(this);
91}
92 
93void MessageQueue::init(const sp<SurfaceFlinger>& flinger) {
94    mFlinger = flinger;
95    mLooper = new Looper(true);
96    mHandler = new Handler(*this);
97}

main方法是surfaceflinger的入口。该方法中关注到sp<SurfaceFlinger> flinger = surfaceflinger::createSurfaceFlinger()。这里创建了surfaceFlinger，实际上这里的sp隐含了一个方法调用——onFirstRef()。这个方法有点特殊，在代码层面看不到调用关系。实际上它是当强指针（sp-strong point）第一次被引用时，会被调用。继续可以看到在onFirstRef中执行了mEventQueue的init方法。继续看这个init方法，实际上创建了Looer和handler两个成员。这连个成员的作用是循环接受和发送消息，处理消息的作用。

注意到flinger→init()方法。该方法中调用mCompositionEngine->setRenderEngine(renderengine::RenderEngine::create初始化了renderEngine。renderEngine是用来做软件合成的。

1// Use StartPropertySetThread instead.
2void SurfaceFlinger::init() {
3ALOGI( "SurfaceFlinger's main thread ready to run. "
4"Initializing graphics H/W...");
5Mutex::Autolock _l(mStateLock);
6 
7 
8 
9// Get a RenderEngine for the given display / config (can't fail)
10// TODO(b/77156734): We need to stop casting and use HAL types when possible.
11// Sending maxFrameBufferAcquiredBuffers as the cache size is tightly tuned to single-display.
12mCompositionEngine->setRenderEngine(renderengine::RenderEngine::create(
13renderengine::RenderEngineCreationArgs::Builder()
14.setPixelFormat(static_cast<int32_t>(defaultCompositionPixelFormat))
15.setImageCacheSize(maxFrameBufferAcquiredBuffers)
16.setUseColorManagerment(useColorManagement)
17.setEnableProtectedContext(enable_protected_contents(false))
18.setPrecacheToneMapperShaderOnly(false)
19.setSupportsBackgroundBlur(mSupportsBlur)
20.setContextPriority(
21useContextPriority
22? renderengine::RenderEngine::ContextPriority::REALTIME
23: renderengine::RenderEngine::ContextPriority::MEDIUM)
24.build()));

最后调用flinger->run()方法，进入消息等待中。