android8.1启动过程(七) SystemServer_we1less的博客-CSDN博客
这篇文章说道SystemServer进程主要用于创建系统服务，同时初始化Zygote
调用gCurRuntime->onZygoteInit();本文从这继续解析binder的启动过程。
onZygoteInit AOSP/frameworks/base/cmds/app_process/app_main.cpp
virtual void onZygoteInit()
{
sp proc = ProcessState::self();
ALOGV("App process: starting thread pool.n");
proc->startThreadPool();
}
ProcessState::self(); frameworks/native/libs/binder/ProcessState.cpp
#define BINDER_VM_SIZE ((1 * 1024 * 1024) - sysconf(_SC_PAGE_SIZE) * 2)
sysconf(_SC_PAGE_SIZE)这个代表一页内存大小一般是 4096
这样 BINDER_VM_SIZE = 1M - 8k
#define BINDER_VM_SIZE ((1 * 1024 * 1024) - sysconf(_SC_PAGE_SIZE) * 2) #define DEFAULT_MAX_BINDER_THREADS 15 spProcessState::self() { Mutex::Autolock _l(gProcessMutex); if (gProcess != NULL) { return gProcess; } gProcess = new ProcessState("/dev/binder"); return gProcess; } ProcessState::ProcessState(const char *driver) //驱动文件的名字 /dev/binder : mDriverName(String8(driver)) //这里有打开驱动的代码open_driver , mDriverFD(open_driver(driver)) , mVMStart(MAP_FAILED) , mThreadCountLock(PTHREAD_MUTEX_INITIALIZER) , mThreadCountDecrement(PTHREAD_COND_INITIALIZER) , mExecutingThreadsCount(0) , mMaxThreads(DEFAULT_MAX_BINDER_THREADS) , mStarvationStartTimeMs(0) , mManagesContexts(false) , mBinderContextCheckFunc(NULL) , mBinderContextUserData(NULL) , mThreadPoolStarted(false) , mThreadPoolSeq(1) { if (mDriverFD >= 0) { // mmap the binder, providing a chunk of virtual address space to receive transactions. //内存映射 1M - 8k mVMStart = mmap(0, BINDER_VM_SIZE, PROT_READ, MAP_PRIVATE | MAP_NORESERVE, mDriverFD, 0); if (mVMStart == MAP_FAILED) { // *sigh* ALOGE("Using /dev/binder failed: unable to mmap transaction memory.n"); close(mDriverFD); mDriverFD = -1; mDriverName.clear(); } } LOG_ALWAYS_FATAL_IF(mDriverFD < 0, "Binder driver could not be opened. Terminating."); }
open_driver 打开驱动节点
static int open_driver(const char *driver)
{
//open节点返回文件句柄
int fd = open(driver, O_RDWR | O_CLOEXEC);
if (fd >= 0) {
int vers = 0;
status_t result = ioctl(fd, BINDER_VERSION, &vers);
if (result == -1) {
ALOGE("Binder ioctl to obtain version failed: %s", strerror(errno));
close(fd);
fd = -1;
}
if (result != 0 || vers != BINDER_CURRENT_PROTOCOL_VERSION) {
ALOGE("Binder driver protocol(%d) does not match user space protocol(%d)! ioctl() return value: %d",
vers, BINDER_CURRENT_PROTOCOL_VERSION, result);
close(fd);
fd = -1;
}
//DEFAULT_MAX_BINDER_THREADS 最大binder线程大小 = 15
size_t maxThreads = DEFAULT_MAX_BINDER_THREADS;
result = ioctl(fd, BINDER_SET_MAX_THREADS, &maxThreads);
if (result == -1) {
ALOGE("Binder ioctl to set max threads failed: %s", strerror(errno));
}
} else {
ALOGW("Opening '%s' failed: %sn", driver, strerror(errno));
}
return fd;
}
接下来分析startThreadPool frameworks/native/libs/binder/ProcessState.cpp
void ProcessState::startThreadPool()
{
AutoMutex _l(mLock);
if (!mThreadPoolStarted) {
mThreadPoolStarted = true;
spawnPooledThread(true);
}
}
void ProcessState::spawnPooledThread(bool isMain)
{
if (mThreadPoolStarted) {
//创建binder线程名字 binder-xxx
String8 name = makeBinderThreadName();
ALOGV("Spawning new pooled thread, name=%sn", name.string());
//启动主线程循环
sp t = new PoolThread(isMain);
t->run(name.string());
}
}
//循环线程
class PoolThread : public Thread
{
...
protected:
virtual bool threadLoop()
{
//循环体
IPCThreadState::self()->joinThreadPool(mIsMain);
return false;
}
const bool mIsMain;
};
接下来看 IPCThreadState frameworks/native/libs/binder/IPCThreadState.cpp
从这里就能说明每一个binder线程就对应一个IPCThreadState对象
IPCThreadState* IPCThreadState::self()
{
//初始gHaveTLS == false
if (gHaveTLS) {
restart:
const pthread_key_t k = gTLS;
IPCThreadState* st = (IPCThreadState*)pthread_getspecific(k);
if (st) return st;
return new IPCThreadState;
}
...
pthread_mutex_lock(&gTLSMutex);
if (!gHaveTLS) {
int key_create_value = pthread_key_create(&gTLS, threadDestructor);
if (key_create_value != 0) {
pthread_mutex_unlock(&gTLSMutex);
ALOGW("IPCThreadState::self() unable to create TLS key, expect a crash: %sn",
strerror(key_create_value));
return NULL;
}
gHaveTLS = true;
}
pthread_mutex_unlock(&gTLSMutex);
//执行完毕后回到restart
goto restart;
}
joinThreadPool
void IPCThreadState::joinThreadPool(bool isMain)
{
LOG_THREADPOOL("**** THREAD %p (PID %d) IS JOINING THE THREAD POOLn", (void*)pthread_self(), getpid());
mOut.writeInt32(isMain ? BC_ENTER_LOOPER : BC_REGISTER_LOOPER);
status_t result;
do {
processPendingDerefs();
// now get the next command to be processed, waiting if necessary
//与binder驱动进行相互通信
result = getAndExecuteCommand();
if (result < NO_ERROR && result != TIMED_OUT && result != -EConNREFUSED && result != -EBADF) {
ALOGE("getAndExecuteCommand(fd=%d) returned unexpected error %d, aborting",
mProcess->mDriverFD, result);
abort();
}
// Let this thread exit the thread pool if it is no longer
// needed and it is not the main process thread.
if(result == TIMED_OUT && !isMain) {
break;
}
} while (result != -EConNREFUSED && result != -EBADF);
LOG_THREADPOOL("**** THREAD %p (PID %d) IS LEAVING THE THREAD POOL err=%dn",
(void*)pthread_self(), getpid(), result);
mOut.writeInt32(BC_EXIT_LOOPER);
talkWithDriver(false);
}
总结：
1.打开binder驱动 open_driver
2.映射内存 mmap
3.启动binder线程
4.获取binder线程IPCThreadState对象
5.通知binder驱动已经进入循环
