写给应用开发的 Android Framework 教程是一个系列教程，现在已更新以下内容：
-
Android Framework 学习路途攻略
-
系统开发根底
- Ubuntu 运用快速入门
- Make 构建东西入门
- 了解 Unicode UTF-8 UTF-16 UTF-32
- Linux Shell 脚本编程入门——核心根底语法
- SEAndroid 运用极速上手
- 了解 C++ 的 Memory Order
-
AOSP 上手攻略
- AOSP 极速上手
- 系统开发东西举荐
- 添加 Product
- 添加 C/C++、Java 可执行程序
- 添加 C/C++、Java 库
- 添加配置文件与删去已有模块
- 系统 App 源码添加
- 运用 Android Studio 开发系统 App
- 添加开机自启动 Shell 脚本
-
学穿 Binder 系列
- Binder 根本原理
- Binder 程序示例之 C 言语篇
- Binder 服务注册进程景象分析之C言语篇
- Binder 服务获取与运用进程景象分析之C言语篇
- Binder C++ 程序示例
- Binder C++ 程序分析之主要类解析
- Binder 服务注册进程景象分析之 C++ 篇
-
HAL 与硬件服务
- Kernel 下载与编译
- Linux 驱动开发入门
本文基于 AOSP Android10 r41 源码环境
1. Server 端主张服务注册央求
Server 端主函数的结束如下：
int main(int argc, char const *argv[])
{
//结束驱动初始化
sp<ProcessState> proc(ProcessState::self());
//获得 ServiceManager Binder 署理类
sp<IServiceManager> sm = defaultServiceManager();
//添加 hello 服务
sm->addService(String16("hello"), new BnHelloService());
//敞开线程池，等候远程调用
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
return 0;
}
总共四个流程：
- Binder 初始化
- 调用 defaultServiceManager 函数获取 ServiceManager Binder 署理类
- 主张远程调用,添加 hello 服务
- 敞开线程池，等候远程调用
接下来我们逐一分析上面的 4 个流程
1.1 Binder 初始化
sp<ProcessState> proc(ProcessState::self());
ProcessState 是一个单例类，其 self 方法回来进程全局单例方针，一同单例方针构建的进程中结束 Binder 的初始化。
具体的结束如下：
// /frameworks/native/libs/binder/Static.h
sp<ProcessState> gProcess;
// /frameworks/native/libs/binder/ProcessState.cpp
//ProcessState 是一个单例类
// const char* kDefaultDriver = "/dev/binder";
sp<ProcessState> ProcessState::self()
{
Mutex::Autolock _l(gProcessMutex);
if (gProcess != nullptr) {
return gProcess;
}
//调用结构函数
gProcess = new ProcessState(kDefaultDriver);
return gProcess;
}
ProcessState::ProcessState(const char *driver)
: mDriverName(String8(driver))
, mDriverFD(open_driver(driver)) //关注点1 调用 open_dirver 结束初始化
, mVMStart(MAP_FAILED)
, mThreadCountLock(PTHREAD_MUTEX_INITIALIZER)
, mThreadCountDecrement(PTHREAD_COND_INITIALIZER)
, mExecutingThreadsCount(0)
, mMaxThreads(DEFAULT_MAX_BINDER_THREADS)
, mStarvationStartTimeMs(0)
, mManagesContexts(false)
, mBinderContextCheckFunc(nullptr)
, mBinderContextUserData(nullptr)
, mThreadPoolStarted(false)
, mThreadPoolSeq(1)
, mCallRestriction(CallRestriction::NONE)
{
if (mDriverFD >= 0) {
// mmap the binder, providing a chunk of virtual address space to receive transactions.
//关注点2 调用 mmap 结束映射
mVMStart = mmap(nullptr, BINDER_VM_SIZE, PROT_READ, MAP_PRIVATE | MAP_NORESERVE, mDriverFD, 0);
if (mVMStart == MAP_FAILED) {
// *sigh*
ALOGE("Using %s failed: unable to mmap transaction memory.\n", mDriverName.c_str());
close(mDriverFD);
mDriverFD = -1;
mDriverName.clear();
}
}
LOG_ALWAYS_FATAL_IF(mDriverFD < 0, "Binder driver could not be opened. Terminating.");
}
关注点1，调用 open_driver：
static int open_driver(const char *driver)
{
//运用 open 翻开 /dev/binder 驱动
int fd = open(driver, O_RDWR | O_CLOEXEC);
if (fd >= 0) {
int vers = 0;
//Binder 版别
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;
}
//Binder 协议版别
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;
}
//设置线程数
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: %s\n", driver, strerror(errno));
}
return fd;
}
关注点2 调用 mmap 结束映射
mVMStart = mmap(nullptr, BINDER_VM_SIZE, PROT_READ, MAP_PRIVATE | MAP_NORESERVE, mDriverFD, 0);
1.2 调用 defaultServiceManager 函数获取 ServiceManager Binder 署理类
接下来看看 defaultServiceManager 的结束：
sp<IServiceManager> defaultServiceManager()
{
if (gDefaultServiceManager != nullptr) return gDefaultServiceManager;
{
AutoMutex _l(gDefaultServiceManagerLock);
while (gDefaultServiceManager == nullptr) {
//关注点
gDefaultServiceManager = interface_cast<IServiceManager>(
ProcessState::self()->getContextObject(nullptr));
if (gDefaultServiceManager == nullptr)
sleep(1);
}
}
return gDefaultServiceManager;
}
接下来逐步分析：ProcessState::self()->getContextObject(nullptr) :
sp<IBinder> ProcessState::getContextObject(const sp<IBinder>& /*caller*/)
{
return getStrongProxyForHandle(0);
}
sp<IBinder> ProcessState::getStrongProxyForHandle(int32_t handle)
{
sp<IBinder> result;
AutoMutex _l(mLock);
//1
handle_entry* e = lookupHandleLocked(handle);
//2
if (e != nullptr) {
IBinder* b = e->binder;
if (b == nullptr || !e->refs->attemptIncWeak(this)) {
if (handle == 0) {
Parcel data;
status_t status = IPCThreadState::self()->transact(
0, IBinder::PING_TRANSACTION, data, nullptr, 0);
if (status == DEAD_OBJECT)
return nullptr;
}
//3
b = BpBinder::create(handle);
e->binder = b;
if (b) e->refs = b->getWeakRefs();
result = b;
} else {
result.force_set(b);
e->refs->decWeak(this);
}
}
return result;
}
Vector<handle_entry> mHandleToObject;
ProcessState::handle_entry* ProcessState::lookupHandleLocked(int32_t handle)
{
const size_t N=mHandleToObject.size();
if (N <= (size_t)handle) {
handle_entry e;
e.binder = nullptr;
e.refs = nullptr;
status_t err = mHandleToObject.insertAt(e, N, handle+1-N);
if (err < NO_ERROR) return nullptr;
}
return &mHandleToObject.editItemAt(handle);
}
-
lookupHandleLocked()，是在
Vector mHandleToObject(注意这儿不是 c++ 规范库中的 Vector)中查找是否有句柄为 handle 的handle_entry 方针。有的话，则回来该 handle_entry 方针；没有的话，则新建 handle 对应的 handle_entry，并将其添加到 mHandleToObject 中，然后再回来。mHandleToObject 是用于保存各个 IBinder 署理方针的 Vector 数组，它相当于一个缓冲。 -
很显然，此时 e! = NULL 为 true，进入 if(e!=NULL) 中。而此时 e->binder=NULL，并且 handle=0；则调 IPCThreadState::self()->transact() 检验去和 Binder 驱动通讯(检验去ping内核中Binder驱动)。因为 Binder 驱动已启动，ping通讯是能够成功的。
-
接着，调用 BpBinder::create(handle)（其内部实践是 new 一个 BpBinder 方针），回来的 BpBinder 赋值给 e->binder。然后，将该 BpBinder 方针回来。
从上面的分析知道 ProcessState::self()->getContextObject(nullptr) 回来了一个 BpBinder 方针，其内部的 mHandle 值为 0。
接下来调用 interface_cast<IServiceManager> 宏，将 BpBinder 转换为 IServiceManager
下面看下 interface_cast<IServiceManager>
template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj)
{
return INTERFACE::asInterface(obj);
}
//模板翻开
inline sp<IServiceManager> interface_cast(const sp<IBinder>& obj)
{
return IServiceManager::asInterface(obj);
}
asInterface 是 IServiceManager 类的一个静态方法，通过 IMPLEMENT_META_INTERFACE 宏结束。宏翻开后如下：
::android::sp<IServiceManager> IServiceManager::asInterface(
const ::android::sp<::android::IBinder>& obj)
{
::android::sp<IServiceManager> intr;
if (obj != nullptr) {
intr = static_cast<IServiceManager*>(
//BpBinder 的 queryLocalInterface 函数回来 null
obj->queryLocalInterface(
IServiceManager::descriptor).get());
if (intr == nullptr) { //走这儿
//obj 类型是 BpBinder
intr = new BpServiceManager(obj);
}
}
return intr;
}
asInterface 函数实践是 new 了一个 BpServiceManager，并传入了 obj，obj 的类型是 BpBinder。
回到初步处，我们把新构建的 BpServiceManager 赋值给了全局变量 gDefaultServiceManager，后边我们就能够通过这个署理类主张远程调用。
1.3 主张远程调用,添加 hello 服务
sm->addService(String16("hello"), new BnHelloService());
sm 的实践类型是 BpServiceManager ，我们通过这个 Binder 署理类主张远程调用。
BnHelloService 是 Hello 服务对应的 Binder 本地类。
接下来看看 addService 的具体结束：
// frameworks/native/libs/binder/include/binder/IServiceManager.h
//声明
//后两个参数带默认值
virtual status_t addService(const String16& name, const sp<IBinder>& service,
bool allowIsolated = false,
int dumpsysFlags = DUMP_FLAG_PRIORITY_DEFAULT) = 0;
// frameworks/native/libs/binder/IServiceManager.cpp
//结束
virtual status_t addService(const String16& name, const sp<IBinder>& service,
bool allowIsolated, int dumpsysPriority)
{
Parcel data, reply;
//关注点1
//写入头数据
data.writeInterfaceToken(IServiceManager::getInterfaceDescriptor());
data.writeString16(name);
//将 BnHelloService 封装到 flat_binder_object 结构体中
data.writeStrongBinder(service);
data.writeInt32(allowIsolated ? 1 : 0);
data.writeInt32(dumpsysPriority);
//关注点2
status_t err = remote()->transact(ADD_SERVICE_TRANSACTION, data, &reply);
return err == NO_ERROR ? reply.readExceptionCode() : err;
}
关注点1：构建好数据 Parcel data
关注点2 ：调用 remote()->transact 主张远程调用，接下来看看 remote() 是什么，是怎样主张远程调用的。
依据之前的类关系分析，找到 remote() 函数的结束,在 IServiceManager 的父类 BpRefBase :
// frameworks/native/libs/binder/include/binder/Binder.h
class BpRefBase : public virtual RefBase
{
protected:
//......
inline IBinder* remote() { return mRemote; }
inline IBinder* remote() const { return mRemote; }
private:
//......
IBinder* const mRemote;
//......
};
remote() 仅仅简单的回来 mRmote 成员，接下来我们找找 mRemote 是什么时分赋值的？
前面的分析, IServiceManager::asInterface 中 new 了一个 BpServiceManager：
//调用
//obj 的类型是 BpBinder ，内部的 handle = 0
intr = new BpServiceManager(obj);
//结束
explicit BpServiceManager(const sp<IBinder>& impl)
: BpInterface<IServiceManager>(impl)
{
}
BpServiceManager 持续调用父类 BpInterface<IServiceManager> 结构函数：
template<typename INTERFACE>
inline BpInterface<INTERFACE>::BpInterface(const sp<IBinder>& remote)
: BpRefBase(remote)
{
}
持续调用父类 BpRefBase 的结构函数：
BpRefBase::BpRefBase(const sp<IBinder>& o)
: mRemote(o.get()), mRefs(nullptr), mState(0)
{
extendObjectLifetime(OBJECT_LIFETIME_WEAK);
if (mRemote) {
mRemote->incStrong(this); // Removed on first IncStrong().
mRefs = mRemote->createWeak(this); // Held for our entire lifetime.
}
}
这儿把传入的 BpBinder (hanle = 0) 赋值给 mRemote。
remote() 函数回来传入的 BpBinder
回过头来我们的 remote()->transact 实践就是调用的 BpBinder 的 transact 函数：
status_t BpBinder::transact(
uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
// Once a binder has died, it will never come back to life.
if (mAlive) {
status_t status = IPCThreadState::self()->transact(
mHandle, code, data, reply, flags);
if (status == DEAD_OBJECT) mAlive = 0;
return status;
}
return DEAD_OBJECT;
}
实践调用的是 IPCThreadState 单例类的 transact 函数：
IPCThreadState* IPCThreadState::self()
{
if (gHaveTLS) {
restart:
const pthread_key_t k = gTLS;
IPCThreadState* st = (IPCThreadState*)pthread_getspecific(k);
if (st) return st;
return new IPCThreadState;
}
if (gShutdown) {
ALOGW("Calling IPCThreadState::self() during shutdown is dangerous, expect a crash.\n");
return nullptr;
}
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: %s\n",
strerror(key_create_value));
return nullptr;
}
gHaveTLS = true;
}
pthread_mutex_unlock(&gTLSMutex);
goto restart;
}
这儿用到了线程本地变量的概念，暂时不用管具体细节，横竖第一次调用会执行到：
//调用
new IPCThreadState
//结束
IPCThreadState::IPCThreadState()
: mProcess(ProcessState::self()),
mWorkSource(kUnsetWorkSource),
mPropagateWorkSource(false),
mStrictModePolicy(0),
mLastTransactionBinderFlags(0),
mCallRestriction(mProcess->mCallRestriction)
{
pthread_setspecific(gTLS, this);
clearCaller();
mIn.setDataCapacity(256);
mOut.setDataCapacity(256);
mIPCThreadStateBase = IPCThreadStateBase::self();
}
结构函数根本就是对成员变量进行赋值，暂时不用关怀细节。
接下来看见我们最关怀的 transact
status_t IPCThreadState::transact(int32_t handle,
uint32_t code, const Parcel& data,
Parcel* reply, uint32_t flags)
{
status_t err;
flags |= TF_ACCEPT_FDS;
IF_LOG_TRANSACTIONS() {
TextOutput::Bundle _b(alog);
alog << "BC_TRANSACTION thr " << (void*)pthread_self() << " / hand "
<< handle << " / code " << TypeCode(code) << ": "
<< indent << data << dedent << endl;
}
LOG_ONEWAY(">>>> SEND from pid %d uid %d %s", getpid(), getuid(),
(flags & TF_ONE_WAY) == 0 ? "READ REPLY" : "ONE WAY");
//关注点1
err = writeTransactionData(BC_TRANSACTION, flags, handle, code, data, nullptr);
if (err != NO_ERROR) {
if (reply) reply->setError(err);
return (mLastError = err);
}
if ((flags & TF_ONE_WAY) == 0) { //代码走这
if (UNLIKELY(mCallRestriction != ProcessState::CallRestriction::NONE)) {
if (mCallRestriction == ProcessState::CallRestriction::ERROR_IF_NOT_ONEWAY) {
ALOGE("Process making non-oneway call but is restricted.");
CallStack::logStack("non-oneway call", CallStack::getCurrent(10).get(),
ANDROID_LOG_ERROR);
} else /* FATAL_IF_NOT_ONEWAY */ {
LOG_ALWAYS_FATAL("Process may not make oneway calls.");
}
}
#if 0
if (code == 4) { // relayout
ALOGI(">>>>>> CALLING transaction 4");
} else {
ALOGI(">>>>>> CALLING transaction %d", code);
}
#endif
if (reply) { //代码走这
//关注点2
err = waitForResponse(reply);
} else {
Parcel fakeReply;
err = waitForResponse(&fakeReply);
}
#if 0
if (code == 4) { // relayout
ALOGI("<<<<<< RETURNING transaction 4");
} else {
ALOGI("<<<<<< RETURNING transaction %d", code);
}
#endif
IF_LOG_TRANSACTIONS() {
TextOutput::Bundle _b(alog);
alog << "BR_REPLY thr " << (void*)pthread_self() << " / hand "
<< handle << ": ";
if (reply) alog << indent << *reply << dedent << endl;
else alog << "(none requested)" << endl;
}
} else {
err = waitForResponse(nullptr, nullptr);
}
return err;
}
关注点 1 主要是结构需求发送的数据：
status_t IPCThreadState::writeTransactionData(int32_t cmd, uint32_t binderFlags,
int32_t handle, uint32_t code, const Parcel& data, status_t* statusBuffer)
{
binder_transaction_data tr;
tr.target.ptr = 0; /* Don't pass uninitialized stack data to a remote process */
tr.target.handle = handle;
tr.code = code;
tr.flags = binderFlags;
tr.cookie = 0;
tr.sender_pid = 0;
tr.sender_euid = 0;
const status_t err = data.errorCheck();
if (err == NO_ERROR) {
tr.data_size = data.ipcDataSize();
tr.data.ptr.buffer = data.ipcData();
tr.offsets_size = data.ipcObjectsCount()*sizeof(binder_size_t);
tr.data.ptr.offsets = data.ipcObjects();
} else if (statusBuffer) {
tr.flags |= TF_STATUS_CODE;
*statusBuffer = err;
tr.data_size = sizeof(status_t);
tr.data.ptr.buffer = reinterpret_cast<uintptr_t>(statusBuffer);
tr.offsets_size = 0;
tr.data.ptr.offsets = 0;
} else {
return (mLastError = err);
}
mOut.writeInt32(cmd);
mOut.write(&tr, sizeof(tr));
return NO_ERROR;
}
关注点2：主张远程调用
status_t IPCThreadState::waitForResponse(Parcel *reply, status_t *acquireResult)
{
uint32_t cmd;
int32_t err;
while (1) {
//主张远程调用
//主张远程调用后，其时线程阻塞，ServiceManager 被唤醒并一同收到数据，ServiceManager 的处理能够参考 c 言语部分的分析
if ((err=talkWithDriver()) < NO_ERROR) break;
err = mIn.errorCheck();
if (err < NO_ERROR) break;
if (mIn.dataAvail() == 0) continue;
//ServiceManager 处理完添加服务央求，进入阻塞装填，回来数据给 Server 端
cmd = (uint32_t)mIn.readInt32();
IF_LOG_COMMANDS() {
alog << "Processing waitForResponse Command: "
<< getReturnString(cmd) << endl;
}
switch (cmd) {
case BR_TRANSACTION_COMPLETE:
if (!reply && !acquireResult) goto finish;
break;
case BR_DEAD_REPLY:
err = DEAD_OBJECT;
goto finish;
case BR_FAILED_REPLY:
err = FAILED_TRANSACTION;
goto finish;
case BR_ACQUIRE_RESULT:
{
ALOG_ASSERT(acquireResult != NULL, "Unexpected brACQUIRE_RESULT");
const int32_t result = mIn.readInt32();
if (!acquireResult) continue;
*acquireResult = result ? NO_ERROR : INVALID_OPERATION;
}
goto finish;
case BR_REPLY: //代码走这儿
{
binder_transaction_data tr;
err = mIn.read(&tr, sizeof(tr));
ALOG_ASSERT(err == NO_ERROR, "Not enough command data for brREPLY");
if (err != NO_ERROR) goto finish;
if (reply) { //走这儿
if ((tr.flags & TF_STATUS_CODE) == 0) {
//reply 成员变量赋值
reply->ipcSetDataReference(
reinterpret_cast<const uint8_t*>(tr.data.ptr.buffer),
tr.data_size,
reinterpret_cast<const binder_size_t*>(tr.data.ptr.offsets),
tr.offsets_size/sizeof(binder_size_t),
freeBuffer, this);
} else {
err = *reinterpret_cast<const status_t*>(tr.data.ptr.buffer);
freeBuffer(nullptr,
reinterpret_cast<const uint8_t*>(tr.data.ptr.buffer),
tr.data_size,
reinterpret_cast<const binder_size_t*>(tr.data.ptr.offsets),
tr.offsets_size/sizeof(binder_size_t), this);
}
} else {
freeBuffer(nullptr,
reinterpret_cast<const uint8_t*>(tr.data.ptr.buffer),
tr.data_size,
reinterpret_cast<const binder_size_t*>(tr.data.ptr.offsets),
tr.offsets_size/sizeof(binder_size_t), this);
continue;
}
}
goto finish;
default:
err = executeCommand(cmd);
if (err != NO_ERROR) goto finish;
break;
}
}
finish:
if (err != NO_ERROR) {
if (acquireResult) *acquireResult = err;
if (reply) reply->setError(err);
mLastError = err;
}
return err;
}
// 看着挺凌乱，实践就三个流程
// 1. 结构要发送的数据
// 2. ioctl + BINDER_WRITE_READ 主张远程调用
// 2. 解析收到的数据
status_t IPCThreadState::talkWithDriver(bool doReceive)
{
if (mProcess->mDriverFD <= 0) {
return -EBADF;
}
binder_write_read bwr;
// Is the read buffer empty?
const bool needRead = mIn.dataPosition() >= mIn.dataSize();
// We don't want to write anything if we are still reading
// from data left in the input buffer and the caller
// has requested to read the next data.
const size_t outAvail = (!doReceive || needRead) ? mOut.dataSize() : 0;
bwr.write_size = outAvail;
bwr.write_buffer = (uintptr_t)mOut.data();
// This is what we'll read.
if (doReceive && needRead) {
bwr.read_size = mIn.dataCapacity();
bwr.read_buffer = (uintptr_t)mIn.data();
} else {
bwr.read_size = 0;
bwr.read_buffer = 0;
}
IF_LOG_COMMANDS() {
TextOutput::Bundle _b(alog);
if (outAvail != 0) {
alog << "Sending commands to driver: " << indent;
const void* cmds = (const void*)bwr.write_buffer;
const void* end = ((const uint8_t*)cmds)+bwr.write_size;
alog << HexDump(cmds, bwr.write_size) << endl;
while (cmds < end) cmds = printCommand(alog, cmds);
alog << dedent;
}
alog << "Size of receive buffer: " << bwr.read_size
<< ", needRead: " << needRead << ", doReceive: " << doReceive << endl;
}
// Return immediately if there is nothing to do.
if ((bwr.write_size == 0) && (bwr.read_size == 0)) return NO_ERROR;
bwr.write_consumed = 0;
bwr.read_consumed = 0;
status_t err;
do {
IF_LOG_COMMANDS() {
alog << "About to read/write, write size = " << mOut.dataSize() << endl;
}
#if defined(__ANDROID__)
//主张远程调用
if (ioctl(mProcess->mDriverFD, BINDER_WRITE_READ, &bwr) >= 0)
err = NO_ERROR;
else
err = -errno;
#else
err = INVALID_OPERATION;
#endif
if (mProcess->mDriverFD <= 0) {
err = -EBADF;
}
IF_LOG_COMMANDS() {
alog << "Finished read/write, write size = " << mOut.dataSize() << endl;
}
} while (err == -EINTR);
IF_LOG_COMMANDS() {
alog << "Our err: " << (void*)(intptr_t)err << ", write consumed: "
<< bwr.write_consumed << " (of " << mOut.dataSize()
<< "), read consumed: " << bwr.read_consumed << endl;
}
if (err >= NO_ERROR) {
if (bwr.write_consumed > 0) {
if (bwr.write_consumed < mOut.dataSize())
mOut.remove(0, bwr.write_consumed);
else {
mOut.setDataSize(0);
processPostWriteDerefs();
}
}
if (bwr.read_consumed > 0) {
mIn.setDataSize(bwr.read_consumed);
mIn.setDataPosition(0);
}
IF_LOG_COMMANDS() {
TextOutput::Bundle _b(alog);
alog << "Remaining data size: " << mOut.dataSize() << endl;
alog << "Received commands from driver: " << indent;
const void* cmds = mIn.data();
const void* end = mIn.data() + mIn.dataSize();
alog << HexDump(cmds, mIn.dataSize()) << endl;
while (cmds < end) cmds = printReturnCommand(alog, cmds);
alog << dedent;
}
return NO_ERROR;
}
return err;
}
至此，添加服务的进程就分析完了
1.4 敞开线程池，等候远程调用
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();
startThreadPool:
void ProcessState::startThreadPool()
{
AutoMutex _l(mLock);
if (!mThreadPoolStarted) {
mThreadPoolStarted = true;
spawnPooledThread(true);
}
}
void ProcessState::spawnPooledThread(bool isMain)
{
if (mThreadPoolStarted) {
String8 name = makeBinderThreadName();
ALOGV("Spawning new pooled thread, name=%s\n", name.string());
sp<Thread> t = new PoolThread(isMain);
t->run(name.string());
}
}
class PoolThread : public Thread
{
public:
explicit PoolThread(bool isMain)
: mIsMain(isMain)
{
}
protected:
virtual bool threadLoop()
{
IPCThreadState::self()->joinThreadPool(mIsMain);
return false;
}
const bool mIsMain;
};
起一个新的线程调用 IPCThreadState::self()->joinThreadPool：
void IPCThreadState::joinThreadPool(bool isMain)
{
LOG_THREADPOOL("**** THREAD %p (PID %d) IS JOINING THE THREAD POOL\n", (void*)pthread_self(), getpid());
mOut.writeInt32(isMain ? BC_ENTER_LOOPER : BC_REGISTER_LOOPER);
status_t result;
do { //进入循环
processPendingDerefs();
// now get the next command to be processed, waiting if necessary
//读数据，处理数据
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=%d\n",
(void*)pthread_self(), getpid(), result);
mOut.writeInt32(BC_EXIT_LOOPER);
talkWithDriver(false);
}
status_t IPCThreadState::getAndExecuteCommand()
{
status_t result;
int32_t cmd;
//读数据
result = talkWithDriver();
if (result >= NO_ERROR) {
size_t IN = mIn.dataAvail();
if (IN < sizeof(int32_t)) return result;
cmd = mIn.readInt32();
IF_LOG_COMMANDS() {
alog << "Processing top-level Command: "
<< getReturnString(cmd) << endl;
}
pthread_mutex_lock(&mProcess->mThreadCountLock);
mProcess->mExecutingThreadsCount++;
if (mProcess->mExecutingThreadsCount >= mProcess->mMaxThreads &&
mProcess->mStarvationStartTimeMs == 0) {
mProcess->mStarvationStartTimeMs = uptimeMillis();
}
pthread_mutex_unlock(&mProcess->mThreadCountLock);
//处理数据
result = executeCommand(cmd);
pthread_mutex_lock(&mProcess->mThreadCountLock);
mProcess->mExecutingThreadsCount--;
if (mProcess->mExecutingThreadsCount < mProcess->mMaxThreads &&
mProcess->mStarvationStartTimeMs != 0) {
int64_t starvationTimeMs = uptimeMillis() - mProcess->mStarvationStartTimeMs;
if (starvationTimeMs > 100) {
ALOGE("binder thread pool (%zu threads) starved for %" PRId64 " ms",
mProcess->mMaxThreads, starvationTimeMs);
}
mProcess->mStarvationStartTimeMs = 0;
}
pthread_cond_broadcast(&mProcess->mThreadCountDecrement);
pthread_mutex_unlock(&mProcess->mThreadCountLock);
}
return result;
}
全体思路和 C 言语中的 binder_loop 大体类似
