1. Native 层多线程分析
1.1 客户端线程相关初始化
在 [Binder 程序示例之C++篇]() 中,客户端是一个单线程程序:
int main(int argc, char const *argv[])
{
//使用 ProcessState 类完成 binder 驱动的初始化
sp<ProcessState> proc(ProcessState::self());
//获取 hello 服务
sp<IServiceManager> sm = defaultServiceManager();
//返回的是 BpBinder 指针
sp<IBinder> binder = sm->getService(String16("hello"));
sp<IHelloService> service =
interface_cast<IHelloService>(binder);
if (binder == 0)
{
ALOGI("can't get hello service\n");
return -1;
}
//发起远程调用
service->sayHello();
int cnt = service->sayHelloTo("nihao");
ALOGI("client call sayhello_to, cnt = %d", cnt);
return 0;
}
从 [Binder 服务注册过程情景分析之 C++ 篇]() 的分析中,我们知道 defaultServiceManager
会调用到如下函数:
status_t status = IPCThreadState::self()->transact(0, IBinder::PING_TRANSACTION, data, nullptr, 0);
transact
最终会调用 ioctl , 陷入内核态,调用到 binder_ioclt 函数
static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
//......
//从 proc 的 threads 红黑树中找 pid 相同的 thread ,没有就新建一个
thread = binder_get_thread(proc);
//......
}
接着我们看下 binder_get_thread 的具体实现:
//参数是当前用户进程(Client 端)对应的 binder_proc
static struct binder_thread *binder_get_thread(struct binder_proc *proc)
{
struct binder_thread *thread;
struct binder_thread *new_thread;
binder_inner_proc_lock(proc); //加锁
//第一次执行
thread = binder_get_thread_ilocked(proc, NULL);
binder_inner_proc_unlock(proc);
if (!thread) {
//构造一个新的 binder_thread
new_thread = kzalloc(sizeof(*thread), GFP_KERNEL);
if (new_thread == NULL)
return NULL;
binder_inner_proc_lock(proc);
//第二次执行
thread = binder_get_thread_ilocked(proc, new_thread);
binder_inner_proc_unlock(proc);
if (thread != new_thread)
kfree(new_thread);
}
return thread;
}
//第一次执行
static struct binder_thread *binder_get_thread_ilocked(
struct binder_proc *proc, struct binder_thread *new_thread)
{
struct binder_thread *thread = NULL;
struct rb_node *parent = NULL;
struct rb_node **p = &proc->threads.rb_node;
printk("binder_get_thread_ilocked, *p is %p", );
// 通过 pid 查找到 binder_thread 结构体,还没插入过数据,所以这里查找到的是 NULL
while (*p) {
parent = *p;
thread = rb_entry(parent, struct binder_thread, rb_node);
if (current->pid < thread->pid)
p = &(*p)->rb_left;
else if (current->pid > thread->pid)
p = &(*p)->rb_right;
else
return thread;
}
if (!new_thread) //直接返回 NULL
return NULL;
//......
}
//第二次执行
static struct binder_thread *binder_get_thread_ilocked(
struct binder_proc *proc, struct binder_thread *new_thread)
{
struct binder_thread *thread = NULL;
struct rb_node *parent = NULL;
struct rb_node **p = &proc->threads.rb_node;
printk("binder_get_thread_ilocked, *p is %p", );
//仍然查找不到
while (*p) {
parent = *p;
thread = rb_entry(parent, struct binder_thread, rb_node);
if (current->pid < thread->pid)
p = &(*p)->rb_left;
else if (current->pid > thread->pid)
p = &(*p)->rb_right;
else
return thread;
}
if (!new_thread)
return NULL;
//配置新构建的 binder_proc
thread = new_thread;
binder_stats_created(BINDER_STAT_THREAD);
thread->proc = proc;
thread->pid = current->pid;
get_task_struct(current);
thread->task = current;
atomic_set(&thread->tmp_ref, 0);
init_waitqueue_head(&thread->wait);
INIT_LIST_HEAD(&thread->todo);
rb_link_node(&thread->rb_node, parent, p); //插入到 proc 的 threads 红黑树中
rb_insert_color(&thread->rb_node, &proc->threads);
thread->looper_need_return = true;
thread->return_error.work.type = BINDER_WORK_RETURN_ERROR;
thread->return_error.cmd = BR_OK;
thread->reply_error.work.type = BINDER_WORK_RETURN_ERROR;
thread->reply_error.cmd = BR_OK;
INIT_LIST_HEAD(&new_thread->waiting_thread_node);
return thread;
}
通过源码分析,可以看出 binder_get_thread 函数:
- 构建并初始化了一个 binder_thread 结构体,该结构体与用户线程相对应
- 同时,将该结构体插入到了 binder_proc->threads 红黑树中
当我们调用 getService
和 service->sayHello()
发起远程调用时,和 defaultServiceManager
类似,也会陷入内核,进入 binder_ioctl
函数。不同的是,当调用到 binder_get_thread
函数时,会直接从红黑树中查找到之前插入的数据并返回。
1.2 服务端线程相关初始化
在 [Binder 程序示例之C++篇]() 中,服务端通过以下代码开启了线程池:
int main(int argc, char const *argv[])
{
//使用 ProcessState 类完成 binder 驱动的初始化
sp<ProcessState> proc(ProcessState::self());
//注册服务
sp<IServiceManager> sm = defaultServiceManager();
sm->addService(String16("hello"), new BnHelloService());
//开启 binder 线程池
ProcessState::self()->startThreadPool();
//加入线程池
IPCThreadState::self()->joinThreadPool();
return 0;
}
和客户端相同,当调用 defaultServiceManager
时,会回调到内核的 binder_ioctl 函数,进一步会调用到binder_get_thread
函数 , 在 binder_get_thread
函数中,构建新的 binder_thread 结构体,并插入 binder_proc->threads 红黑树中。
接着会调用 ProcessState::self()->startThreadPool()
开启线程池:
void ProcessState::startThreadPool()
{
AutoMutex _l(mLock);
if (!mThreadPoolStarted) {
mThreadPoolStarted = true;
spawnPooledThread(true); //创建线程,此处的参数true表示主线程
}
}
void ProcessState::spawnPooledThread(bool isMain)
{
if (mThreadPoolStarted) {
String8 name = makeBinderThreadName(); //Binder线程名称
ALOGV("Spawning new pooled thread, name=%s\n", name.string());
sp<Thread> t = new PoolThread(isMain); //isMain为true表示主线程
t->run(name.string());
}
}
String8 ProcessState::makeBinderThreadName() {
int32_t s = android_atomic_add(1, &mThreadPoolSeq);
pid_t pid = getpid();
String8 name;
name.appendFormat("Binder:%d_%X", pid, s);//格式为Binder:pid_s(其中pid为进程号;s为序列号,每次累加1)
return name;
}
//继承自 Thread,通过 run 启动,启动后会执行 threadLoop 函数
class PoolThread : public Thread
{
public:
explicit PoolThread(bool isMain)
: mIsMain(isMain)
{
}
protected:
virtual bool threadLoop()
{
IPCThreadState::self()->joinThreadPool(mIsMain); //将当前线程加入线程池,mIsMain为true
return false;
}
const bool mIsMain;
};
void IPCThreadState::joinThreadPool(bool isMain)
{
//线程进入循环,isMain为true表示主线程, false表示Binder驱动通知应用进程创建的线程
//告诉驱动,进入循环了
mOut.writeInt32(isMain ? BC_ENTER_LOOPER : BC_REGISTER_LOOPER);
status_t result;
do {
processPendingDerefs(); // 清除队列的引用
result = getAndExecuteCommand(); //获取并执行指令
// ........
// 非主线程且timeout,则跳出循环,结束线程(主线程不会退出)
if(result == TIMED_OUT && !isMain) {
break;
}
} while (result != -ECONNREFUSED && result != -EBADF);
........
mOut.writeInt32(BC_EXIT_LOOPER);// 通知Binder驱动线程退出
talkWithDriver(false); // false表示不读Binder驱动数据,只写
}
接着我们来看 getAndExecuteCommand()
:
status_t IPCThreadState::getAndExecuteCommand()
{
status_t result;
int32_t cmd;
//关注点1 读取数据,同时会写入 BC_ENTER_LOOPER
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);
//处理读到的数据
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;
}
接着看 talkWithDriver
:
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__)
// 通过 ioctl 与驱动交互
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;
}
ioctl 进入内核,调用到 binder_ioctl,和之前介绍的情况一样,这里同样会创建一个 binder_thread,同时会插入 binder_proc->threads 红黑树。
接着会处理传入的 BC_ENTER_LOOPER 命令
static int binder_thread_write(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed)
{
uint32_t cmd;
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
while (ptr < end && thread->return_error == BR_OK) {
//拷贝用户空间的cmd命令,此时为BC_ENTER_LOOPER
if (get_user(cmd, (uint32_t __user *)ptr)) -EFAULT;
ptr += sizeof(uint32_t);
switch (cmd) {
case BC_REGISTER_LOOPER:
if (thread->looper & BINDER_LOOPER_STATE_ENTERED) {
//出错原因:线程调用完 BC_ENTER_LOOPER,不能执行该分支
thread->looper |= BINDER_LOOPER_STATE_INVALID;
} else if (proc->requested_threads == 0) {
//出错原因:没有请求就创建线程
thread->looper |= BINDER_LOOPER_STATE_INVALID;
} else {
proc->requested_threads--;
proc->requested_threads_started++;
}
thread->looper |= BINDER_LOOPER_STATE_REGISTERED;
break;
case BC_ENTER_LOOPER:
if (thread->looper & BINDER_LOOPER_STATE_REGISTERED) {
//出错原因:线程调用完BC_REGISTER_LOOPER,不能立刻执行该分支
thread->looper |= BINDER_LOOPER_STATE_INVALID;
}
//创建Binder主线程
thread->looper |= BINDER_LOOPER_STATE_ENTERED;
break;
case BC_EXIT_LOOPER:
thread->looper |= BINDER_LOOPER_STATE_EXITED;
break;
}
...
}
*consumed = ptr - buffer;
}
return 0;
}
处理 BC_ENTER_LOOPER 就是设置 thread->looper |= BINDER_LOOPER_STATE_ENTERED
接着会调用 binder_thread_read 读数据:
static int binder_thread_read(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed, int non_block)
{
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
int ret = 0;
int wait_for_proc_work;
if (*consumed == 0) {
if (put_user(BR_NOOP, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
}
retry:
binder_inner_proc_lock(proc);
wait_for_proc_work = binder_available_for_proc_work_ilocked(thread);
binder_inner_proc_unlock(proc);
thread->looper |= BINDER_LOOPER_STATE_WAITING;
trace_binder_wait_for_work(wait_for_proc_work,
!!thread->transaction_stack,
!binder_worklist_empty(proc, &thread->todo));
if (wait_for_proc_work) {
if (!(thread->looper & (BINDER_LOOPER_STATE_REGISTERED |
BINDER_LOOPER_STATE_ENTERED))) {
binder_user_error("%d:%d ERROR: Thread waiting for process work before calling BC_REGISTER_LOOPER or BC_ENTER_LOOPER (state %x)\n",
proc->pid, thread->pid, thread->looper);
wait_event_interruptible(binder_user_error_wait,
binder_stop_on_user_error < 2);
}
binder_restore_priority(current, proc->default_priority);
}
if (non_block) {
if (!binder_has_work(thread, wait_for_proc_work))
ret = -EAGAIN;
} else {
// 当前线程加入到 proc->waiting_threads,然后休眠,等待唤醒
ret = binder_wait_for_work(thread, wait_for_proc_work);
}
thread->looper &= ~BINDER_LOOPER_STATE_WAITING;
if (ret)
return ret;
while (1) {
uint32_t cmd;
struct binder_transaction_data_secctx tr;
struct binder_transaction_data *trd = &tr.transaction_data;
struct binder_work *w = NULL;
struct list_head *list = NULL;
struct binder_transaction *t = NULL;
struct binder_thread *t_from;
size_t trsize = sizeof(*trd);
binder_inner_proc_lock(proc);
if (!binder_worklist_empty_ilocked(&thread->todo))
list = &thread->todo;
else if (!binder_worklist_empty_ilocked(&proc->todo) &&
wait_for_proc_work) //走这
list = &proc->todo;
else {
binder_inner_proc_unlock(proc);
/* no data added */
if (ptr - buffer == 4 && !thread->looper_need_return)
goto retry;
break;
}
if (end - ptr < sizeof(tr) + 4) {
binder_inner_proc_unlock(proc);
break;
}
//取链表中第一个数据
w = binder_dequeue_work_head_ilocked(list);
if (binder_worklist_empty_ilocked(&thread->todo))
thread->process_todo = false;
switch (w->type) {
case BINDER_WORK_TRANSACTION: { //走这
binder_inner_proc_unlock(proc);
//拿到 binder_transaction
t = container_of(w, struct binder_transaction, work);
} break;
case BINDER_WORK_RETURN_ERROR: {
struct binder_error *e = container_of(
w, struct binder_error, work);
WARN_ON(e->cmd == BR_OK);
binder_inner_proc_unlock(proc);
if (put_user(e->cmd, (uint32_t __user *)ptr))
return -EFAULT;
cmd = e->cmd;
e->cmd = BR_OK;
ptr += sizeof(uint32_t);
binder_stat_br(proc, thread, e->cmd);
} break;
case BINDER_WORK_TRANSACTION_COMPLETE: {
binder_inner_proc_unlock(proc);
cmd = BR_TRANSACTION_COMPLETE;
if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
binder_stat_br(proc, thread, cmd);
binder_debug(BINDER_DEBUG_TRANSACTION_COMPLETE,
"%d:%d BR_TRANSACTION_COMPLETE\n",
proc->pid, thread->pid);
kfree(w);
binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
} break;
case BINDER_WORK_NODE: {
struct binder_node *node = container_of(w, struct binder_node, work);
int strong, weak;
binder_uintptr_t node_ptr = node->ptr;
binder_uintptr_t node_cookie = node->cookie;
int node_debug_id = node->debug_id;
int has_weak_ref;
int has_strong_ref;
void __user *orig_ptr = ptr;
BUG_ON(proc != node->proc);
strong = node->internal_strong_refs ||
node->local_strong_refs;
weak = !hlist_empty(&node->refs) ||
node->local_weak_refs ||
node->tmp_refs || strong;
has_strong_ref = node->has_strong_ref;
has_weak_ref = node->has_weak_ref;
if (weak && !has_weak_ref) {
node->has_weak_ref = 1;
node->pending_weak_ref = 1;
node->local_weak_refs++;
}
if (strong && !has_strong_ref) {
node->has_strong_ref = 1;
node->pending_strong_ref = 1;
node->local_strong_refs++;
}
if (!strong && has_strong_ref)
node->has_strong_ref = 0;
if (!weak && has_weak_ref)
node->has_weak_ref = 0;
if (!weak && !strong) {
binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"%d:%d node %d u%016llx c%016llx deleted\n",
proc->pid, thread->pid,
node_debug_id,
(u64)node_ptr,
(u64)node_cookie);
rb_erase(&node->rb_node, &proc->nodes);
binder_inner_proc_unlock(proc);
binder_node_lock(node);
/*
* Acquire the node lock before freeing the
* node to serialize with other threads that
* may have been holding the node lock while
* decrementing this node (avoids race where
* this thread frees while the other thread
* is unlocking the node after the final
* decrement)
*/
binder_node_unlock(node);
binder_free_node(node);
} else
binder_inner_proc_unlock(proc);
if (weak && !has_weak_ref)
ret = binder_put_node_cmd(
proc, thread, &ptr, node_ptr,
node_cookie, node_debug_id,
BR_INCREFS, "BR_INCREFS");
if (!ret && strong && !has_strong_ref)
ret = binder_put_node_cmd(
proc, thread, &ptr, node_ptr,
node_cookie, node_debug_id,
BR_ACQUIRE, "BR_ACQUIRE");
if (!ret && !strong && has_strong_ref)
ret = binder_put_node_cmd(
proc, thread, &ptr, node_ptr,
node_cookie, node_debug_id,
BR_RELEASE, "BR_RELEASE");
if (!ret && !weak && has_weak_ref)
ret = binder_put_node_cmd(
proc, thread, &ptr, node_ptr,
node_cookie, node_debug_id,
BR_DECREFS, "BR_DECREFS");
if (orig_ptr == ptr)
binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"%d:%d node %d u%016llx c%016llx state unchanged\n",
proc->pid, thread->pid,
node_debug_id,
(u64)node_ptr,
(u64)node_cookie);
if (ret)
return ret;
} break;
case BINDER_WORK_DEAD_BINDER:
case BINDER_WORK_DEAD_BINDER_AND_CLEAR:
case BINDER_WORK_CLEAR_DEATH_NOTIFICATION: {
struct binder_ref_death *death;
uint32_t cmd;
binder_uintptr_t cookie;
death = container_of(w, struct binder_ref_death, work);
if (w->type == BINDER_WORK_CLEAR_DEATH_NOTIFICATION)
cmd = BR_CLEAR_DEATH_NOTIFICATION_DONE;
else
cmd = BR_DEAD_BINDER;
cookie = death->cookie;
binder_debug(BINDER_DEBUG_DEATH_NOTIFICATION,
"%d:%d %s %016llx\n",
proc->pid, thread->pid,
cmd == BR_DEAD_BINDER ?
"BR_DEAD_BINDER" :
"BR_CLEAR_DEATH_NOTIFICATION_DONE",
(u64)cookie);
if (w->type == BINDER_WORK_CLEAR_DEATH_NOTIFICATION) {
binder_inner_proc_unlock(proc);
kfree(death);
binder_stats_deleted(BINDER_STAT_DEATH);
} else {
binder_enqueue_work_ilocked(
w, &proc->delivered_death);
binder_inner_proc_unlock(proc);
}
if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (put_user(cookie,
(binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(binder_uintptr_t);
binder_stat_br(proc, thread, cmd);
if (cmd == BR_DEAD_BINDER)
goto done; /* DEAD_BINDER notifications can cause transactions */
} break;
}
if (!t)
continue;
BUG_ON(t->buffer == NULL);
if (t->buffer->target_node) {
struct binder_node *target_node = t->buffer->target_node;
struct binder_priority node_prio;
//构建 binder_transaction_data ,用于返回给应用层
trd->target.ptr = target_node->ptr;
trd->cookie = target_node->cookie;
node_prio.sched_policy = target_node->sched_policy;
node_prio.prio = target_node->min_priority;
binder_transaction_priority(current, t, node_prio,
target_node->inherit_rt);
cmd = BR_TRANSACTION;
} else {
trd->target.ptr = 0;
trd->cookie = 0;
cmd = BR_REPLY;
}
trd->code = t->code; //code 表示要调用哪个函数
trd->flags = t->flags;
trd->sender_euid = from_kuid(current_user_ns(), t->sender_euid);
t_from = binder_get_txn_from(t);
if (t_from) {
struct task_struct *sender = t_from->proc->tsk;
trd->sender_pid =
task_tgid_nr_ns(sender,
task_active_pid_ns(current));
} else {
trd->sender_pid = 0;
}
trd->data_size = t->buffer->data_size;
trd->offsets_size = t->buffer->offsets_size;
trd->data.ptr.buffer = (uintptr_t)t->buffer->user_data;
trd->data.ptr.offsets = trd->data.ptr.buffer +
ALIGN(t->buffer->data_size,
sizeof(void *));
tr.secctx = t->security_ctx;
if (t->security_ctx) {
cmd = BR_TRANSACTION_SEC_CTX;
trsize = sizeof(tr);
}
if (put_user(cmd, (uint32_t __user *)ptr)) {
if (t_from)
binder_thread_dec_tmpref(t_from);
binder_cleanup_transaction(t, "put_user failed",
BR_FAILED_REPLY);
return -EFAULT;
}
ptr += sizeof(uint32_t);
//将数据拷贝到应用层
if (copy_to_user(ptr, &tr, trsize)) {
if (t_from)
binder_thread_dec_tmpref(t_from);
binder_cleanup_transaction(t, "copy_to_user failed",
BR_FAILED_REPLY);
return -EFAULT;
}
ptr += trsize;
trace_binder_transaction_received(t);
binder_stat_br(proc, thread, cmd);
binder_debug(BINDER_DEBUG_TRANSACTION,
"%d:%d %s %d %d:%d, cmd %d size %zd-%zd ptr %016llx-%016llx\n",
proc->pid, thread->pid,
(cmd == BR_TRANSACTION) ? "BR_TRANSACTION" :
(cmd == BR_TRANSACTION_SEC_CTX) ?
"BR_TRANSACTION_SEC_CTX" : "BR_REPLY",
t->debug_id, t_from ? t_from->proc->pid : 0,
t_from ? t_from->pid : 0, cmd,
t->buffer->data_size, t->buffer->offsets_size,
(u64)trd->data.ptr.buffer,
(u64)trd->data.ptr.offsets);
if (t_from)
binder_thread_dec_tmpref(t_from);
t->buffer->allow_user_free = 1;
if (cmd != BR_REPLY && !(t->flags & TF_ONE_WAY)) {
binder_inner_proc_lock(thread->proc);
t->to_parent = thread->transaction_stack;
t->to_thread = thread;
thread->transaction_stack = t;
binder_inner_proc_unlock(thread->proc);
} else {
binder_free_transaction(t);
}
break;
}
done:
*consumed = ptr - buffer;
binder_inner_proc_lock(proc);
//应用层创建新线程的条件
if (proc->requested_threads == 0 &&
list_empty(&thread->proc->waiting_threads) &&
proc->requested_threads_started < proc->max_threads &&
(thread->looper & (BINDER_LOOPER_STATE_REGISTERED |
BINDER_LOOPER_STATE_ENTERED)) /* the user-space code fails to */
/*spawn a new thread if we leave this out */) {
proc->requested_threads++;
binder_inner_proc_unlock(proc);
binder_debug(BINDER_DEBUG_THREADS,
"%d:%d BR_SPAWN_LOOPER\n",
proc->pid, thread->pid);
//告知应用层创建新的线程
if (put_user(BR_SPAWN_LOOPER, (uint32_t __user *)buffer))
return -EFAULT;
binder_stat_br(proc, thread, BR_SPAWN_LOOPER);
} else
binder_inner_proc_unlock(proc);
return 0;
}
数据发送方的线程处理
static int binder_thread_write(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed)
{
uint32_t cmd;
struct binder_context *context = proc->context;
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
while (ptr < end && thread->return_error.cmd == BR_OK) {
int ret;
if (get_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
trace_binder_command(cmd);
if (_IOC_NR(cmd) < ARRAY_SIZE(binder_stats.bc)) {
atomic_inc(&binder_stats.bc[_IOC_NR(cmd)]);
atomic_inc(&proc->stats.bc[_IOC_NR(cmd)]);
atomic_inc(&thread->stats.bc[_IOC_NR(cmd)]);
}
switch (cmd) {
case BC_INCREFS:
case BC_ACQUIRE:
case BC_RELEASE:
case BC_DECREFS: {
uint32_t target;
const char *debug_string;
bool strong = cmd == BC_ACQUIRE || cmd == BC_RELEASE;
bool increment = cmd == BC_INCREFS || cmd == BC_ACQUIRE;
struct binder_ref_data rdata;
if (get_user(target, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
ret = -1;
if (increment && !target) {
struct binder_node *ctx_mgr_node;
mutex_lock(&context->context_mgr_node_lock);
ctx_mgr_node = context->binder_context_mgr_node;
if (ctx_mgr_node)
ret = binder_inc_ref_for_node(
proc, ctx_mgr_node,
strong, NULL, &rdata);
mutex_unlock(&context->context_mgr_node_lock);
}
if (ret)
ret = binder_update_ref_for_handle(
proc, target, increment, strong,
&rdata);
if (!ret && rdata.desc != target) {
binder_user_error("%d:%d tried to acquire reference to desc %d, got %d instead\n",
proc->pid, thread->pid,
target, rdata.desc);
}
switch (cmd) {
case BC_INCREFS:
debug_string = "IncRefs";
break;
case BC_ACQUIRE:
debug_string = "Acquire";
break;
case BC_RELEASE:
debug_string = "Release";
break;
case BC_DECREFS:
default:
debug_string = "DecRefs";
break;
}
if (ret) {
binder_user_error("%d:%d %s %d refcount change on invalid ref %d ret %d\n",
proc->pid, thread->pid, debug_string,
strong, target, ret);
break;
}
binder_debug(BINDER_DEBUG_USER_REFS,
"%d:%d %s ref %d desc %d s %d w %d\n",
proc->pid, thread->pid, debug_string,
rdata.debug_id, rdata.desc, rdata.strong,
rdata.weak);
break;
}
case BC_INCREFS_DONE:
case BC_ACQUIRE_DONE: {
binder_uintptr_t node_ptr;
binder_uintptr_t cookie;
struct binder_node *node;
bool free_node;
if (get_user(node_ptr, (binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(binder_uintptr_t);
if (get_user(cookie, (binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(binder_uintptr_t);
node = binder_get_node(proc, node_ptr);
if (node == NULL) {
binder_user_error("%d:%d %s u%016llx no match\n",
proc->pid, thread->pid,
cmd == BC_INCREFS_DONE ?
"BC_INCREFS_DONE" :
"BC_ACQUIRE_DONE",
(u64)node_ptr);
break;
}
if (cookie != node->cookie) {
binder_user_error("%d:%d %s u%016llx node %d cookie mismatch %016llx != %016llx\n",
proc->pid, thread->pid,
cmd == BC_INCREFS_DONE ?
"BC_INCREFS_DONE" : "BC_ACQUIRE_DONE",
(u64)node_ptr, node->debug_id,
(u64)cookie, (u64)node->cookie);
binder_put_node(node);
break;
}
binder_node_inner_lock(node);
if (cmd == BC_ACQUIRE_DONE) {
if (node->pending_strong_ref == 0) {
binder_user_error("%d:%d BC_ACQUIRE_DONE node %d has no pending acquire request\n",
proc->pid, thread->pid,
node->debug_id);
binder_node_inner_unlock(node);
binder_put_node(node);
break;
}
node->pending_strong_ref = 0;
} else {
if (node->pending_weak_ref == 0) {
binder_user_error("%d:%d BC_INCREFS_DONE node %d has no pending increfs request\n",
proc->pid, thread->pid,
node->debug_id);
binder_node_inner_unlock(node);
binder_put_node(node);
break;
}
node->pending_weak_ref = 0;
}
free_node = binder_dec_node_nilocked(node,
cmd == BC_ACQUIRE_DONE, 0);
WARN_ON(free_node);
binder_debug(BINDER_DEBUG_USER_REFS,
"%d:%d %s node %d ls %d lw %d tr %d\n",
proc->pid, thread->pid,
cmd == BC_INCREFS_DONE ? "BC_INCREFS_DONE" : "BC_ACQUIRE_DONE",
node->debug_id, node->local_strong_refs,
node->local_weak_refs, node->tmp_refs);
binder_node_inner_unlock(node);
binder_put_node(node);
break;
}
case BC_ATTEMPT_ACQUIRE:
pr_err("BC_ATTEMPT_ACQUIRE not supported\n");
return -EINVAL;
case BC_ACQUIRE_RESULT:
pr_err("BC_ACQUIRE_RESULT not supported\n");
return -EINVAL;
case BC_FREE_BUFFER: {
binder_uintptr_t data_ptr;
struct binder_buffer *buffer;
if (get_user(data_ptr, (binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(binder_uintptr_t);
buffer = binder_alloc_prepare_to_free(&proc->alloc,
data_ptr);
if (IS_ERR_OR_NULL(buffer)) {
if (PTR_ERR(buffer) == -EPERM) {
binder_user_error(
"%d:%d BC_FREE_BUFFER u%016llx matched unreturned or currently freeing buffer\n",
proc->pid, thread->pid,
(u64)data_ptr);
} else {
binder_user_error(
"%d:%d BC_FREE_BUFFER u%016llx no match\n",
proc->pid, thread->pid,
(u64)data_ptr);
}
break;
}
binder_debug(BINDER_DEBUG_FREE_BUFFER,
"%d:%d BC_FREE_BUFFER u%016llx found buffer %d for %s transaction\n",
proc->pid, thread->pid, (u64)data_ptr,
buffer->debug_id,
buffer->transaction ? "active" : "finished");
if (buffer->transaction) {
buffer->transaction->buffer = NULL;
buffer->transaction = NULL;
}
if (buffer->async_transaction && buffer->target_node) {
struct binder_node *buf_node;
struct binder_work *w;
buf_node = buffer->target_node;
binder_node_inner_lock(buf_node);
BUG_ON(!buf_node->has_async_transaction);
BUG_ON(buf_node->proc != proc);
w = binder_dequeue_work_head_ilocked(
&buf_node->async_todo);
if (!w) {
buf_node->has_async_transaction = false;
} else {
binder_enqueue_work_ilocked(
w, &proc->todo);
binder_wakeup_proc_ilocked(proc);
}
binder_node_inner_unlock(buf_node);
}
trace_binder_transaction_buffer_release(buffer);
binder_transaction_buffer_release(proc, buffer, 0, false);
binder_alloc_free_buf(&proc->alloc, buffer);
break;
}
case BC_TRANSACTION_SG:
case BC_REPLY_SG: {
struct binder_transaction_data_sg tr;
if (copy_from_user(&tr, ptr, sizeof(tr)))
return -EFAULT;
ptr += sizeof(tr);
binder_transaction(proc, thread, &tr.transaction_data,
cmd == BC_REPLY_SG, tr.buffers_size);
break;
}
case BC_TRANSACTION:
case BC_REPLY: {
struct binder_transaction_data tr;
if (copy_from_user(&tr, ptr, sizeof(tr)))
return -EFAULT;
ptr += sizeof(tr);
binder_transaction(proc, thread, &tr,
cmd == BC_REPLY, 0);
break;
}
case BC_REGISTER_LOOPER:
binder_debug(BINDER_DEBUG_THREADS,
"%d:%d BC_REGISTER_LOOPER\n",
proc->pid, thread->pid);
binder_inner_proc_lock(proc);
if (thread->looper & BINDER_LOOPER_STATE_ENTERED) {
thread->looper |= BINDER_LOOPER_STATE_INVALID;
binder_user_error("%d:%d ERROR: BC_REGISTER_LOOPER called after BC_ENTER_LOOPER\n",
proc->pid, thread->pid);
} else if (proc->requested_threads == 0) {
thread->looper |= BINDER_LOOPER_STATE_INVALID;
binder_user_error("%d:%d ERROR: BC_REGISTER_LOOPER called without request\n",
proc->pid, thread->pid);
} else {
proc->requested_threads--;
proc->requested_threads_started++;
}
thread->looper |= BINDER_LOOPER_STATE_REGISTERED;
binder_inner_proc_unlock(proc);
break;
case BC_ENTER_LOOPER:
binder_debug(BINDER_DEBUG_THREADS,
"%d:%d BC_ENTER_LOOPER\n",
proc->pid, thread->pid);
if (thread->looper & BINDER_LOOPER_STATE_REGISTERED) {
thread->looper |= BINDER_LOOPER_STATE_INVALID;
binder_user_error("%d:%d ERROR: BC_ENTER_LOOPER called after BC_REGISTER_LOOPER\n",
proc->pid, thread->pid);
}
thread->looper |= BINDER_LOOPER_STATE_ENTERED;
break;
case BC_EXIT_LOOPER:
binder_debug(BINDER_DEBUG_THREADS,
"%d:%d BC_EXIT_LOOPER\n",
proc->pid, thread->pid);
thread->looper |= BINDER_LOOPER_STATE_EXITED;
break;
case BC_REQUEST_DEATH_NOTIFICATION:
case BC_CLEAR_DEATH_NOTIFICATION: {
uint32_t target;
binder_uintptr_t cookie;
struct binder_ref *ref;
struct binder_ref_death *death = NULL;
if (get_user(target, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (get_user(cookie, (binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(binder_uintptr_t);
if (cmd == BC_REQUEST_DEATH_NOTIFICATION) {
/*
* Allocate memory for death notification
* before taking lock
*/
death = kzalloc(sizeof(*death), GFP_KERNEL);
if (death == NULL) {
WARN_ON(thread->return_error.cmd !=
BR_OK);
thread->return_error.cmd = BR_ERROR;
binder_enqueue_thread_work(
thread,
&thread->return_error.work);
binder_debug(
BINDER_DEBUG_FAILED_TRANSACTION,
"%d:%d BC_REQUEST_DEATH_NOTIFICATION failed\n",
proc->pid, thread->pid);
break;
}
}
binder_proc_lock(proc);
ref = binder_get_ref_olocked(proc, target, false);
if (ref == NULL) {
binder_user_error("%d:%d %s invalid ref %d\n",
proc->pid, thread->pid,
cmd == BC_REQUEST_DEATH_NOTIFICATION ?
"BC_REQUEST_DEATH_NOTIFICATION" :
"BC_CLEAR_DEATH_NOTIFICATION",
target);
binder_proc_unlock(proc);
kfree(death);
break;
}
binder_debug(BINDER_DEBUG_DEATH_NOTIFICATION,
"%d:%d %s %016llx ref %d desc %d s %d w %d for node %d\n",
proc->pid, thread->pid,
cmd == BC_REQUEST_DEATH_NOTIFICATION ?
"BC_REQUEST_DEATH_NOTIFICATION" :
"BC_CLEAR_DEATH_NOTIFICATION",
(u64)cookie, ref->data.debug_id,
ref->data.desc, ref->data.strong,
ref->data.weak, ref->node->debug_id);
binder_node_lock(ref->node);
if (cmd == BC_REQUEST_DEATH_NOTIFICATION) {
if (ref->death) {
binder_user_error("%d:%d BC_REQUEST_DEATH_NOTIFICATION death notification already set\n",
proc->pid, thread->pid);
binder_node_unlock(ref->node);
binder_proc_unlock(proc);
kfree(death);
break;
}
binder_stats_created(BINDER_STAT_DEATH);
INIT_LIST_HEAD(&death->work.entry);
death->cookie = cookie;
ref->death = death;
if (ref->node->proc == NULL) {
ref->death->work.type = BINDER_WORK_DEAD_BINDER;
binder_inner_proc_lock(proc);
binder_enqueue_work_ilocked(
&ref->death->work, &proc->todo);
binder_wakeup_proc_ilocked(proc);
binder_inner_proc_unlock(proc);
}
} else {
if (ref->death == NULL) {
binder_user_error("%d:%d BC_CLEAR_DEATH_NOTIFICATION death notification not active\n",
proc->pid, thread->pid);
binder_node_unlock(ref->node);
binder_proc_unlock(proc);
break;
}
death = ref->death;
if (death->cookie != cookie) {
binder_user_error("%d:%d BC_CLEAR_DEATH_NOTIFICATION death notification cookie mismatch %016llx != %016llx\n",
proc->pid, thread->pid,
(u64)death->cookie,
(u64)cookie);
binder_node_unlock(ref->node);
binder_proc_unlock(proc);
break;
}
ref->death = NULL;
binder_inner_proc_lock(proc);
if (list_empty(&death->work.entry)) {
death->work.type = BINDER_WORK_CLEAR_DEATH_NOTIFICATION;
if (thread->looper &
(BINDER_LOOPER_STATE_REGISTERED |
BINDER_LOOPER_STATE_ENTERED))
binder_enqueue_thread_work_ilocked(
thread,
&death->work);
else {
binder_enqueue_work_ilocked(
&death->work,
&proc->todo);
binder_wakeup_proc_ilocked(
proc);
}
} else {
BUG_ON(death->work.type != BINDER_WORK_DEAD_BINDER);
death->work.type = BINDER_WORK_DEAD_BINDER_AND_CLEAR;
}
binder_inner_proc_unlock(proc);
}
binder_node_unlock(ref->node);
binder_proc_unlock(proc);
} break;
case BC_DEAD_BINDER_DONE: {
struct binder_work *w;
binder_uintptr_t cookie;
struct binder_ref_death *death = NULL;
if (get_user(cookie, (binder_uintptr_t __user *)ptr))
return -EFAULT;
ptr += sizeof(cookie);
binder_inner_proc_lock(proc);
list_for_each_entry(w, &proc->delivered_death,
entry) {
struct binder_ref_death *tmp_death =
container_of(w,
struct binder_ref_death,
work);
if (tmp_death->cookie == cookie) {
death = tmp_death;
break;
}
}
binder_debug(BINDER_DEBUG_DEAD_BINDER,
"%d:%d BC_DEAD_BINDER_DONE %016llx found %pK\n",
proc->pid, thread->pid, (u64)cookie,
death);
if (death == NULL) {
binder_user_error("%d:%d BC_DEAD_BINDER_DONE %016llx not found\n",
proc->pid, thread->pid, (u64)cookie);
binder_inner_proc_unlock(proc);
break;
}
binder_dequeue_work_ilocked(&death->work);
if (death->work.type == BINDER_WORK_DEAD_BINDER_AND_CLEAR) {
death->work.type = BINDER_WORK_CLEAR_DEATH_NOTIFICATION;
if (thread->looper &
(BINDER_LOOPER_STATE_REGISTERED |
BINDER_LOOPER_STATE_ENTERED))
binder_enqueue_thread_work_ilocked(
thread, &death->work);
else {
binder_enqueue_work_ilocked(
&death->work,
&proc->todo);
binder_wakeup_proc_ilocked(proc);
}
}
binder_inner_proc_unlock(proc);
} break;
default:
pr_err("%d:%d unknown command %d\n",
proc->pid, thread->pid, cmd);
return -EINVAL;
}
*consumed = ptr - buffer;
}
return 0;
}
线程不足时,会发消息给应用层,应用层创建新的线程:
status_t IPCThreadState::executeCommand(int32_t cmd)
{
status_t result = NO_ERROR;
switch ((uint32_t)cmd) {
...
case BR_SPAWN_LOOPER:
//创建新的binder线程 【见小节2.3】
mProcess->spawnPooledThread(false);
break;
...
}
return result;
}
Java 进程 Binder 线程初始化
Java 层进程的创建都是通过 Process.start() 方法,向 Zygote 进程发出创建进程的 socket 消息,Zygote 收到消息后会调用 Zygote.forkAndSpecialize() 来 fork 出新进程,在新进程中会调用到 RuntimeInit.nativeZygoteInit 方法,该方法经过 jni 映射,最终会调用到 pp_main.cpp 中的 onZygoteInit
virtual void onZygoteInit() {
//获取ProcessState对象
sp<ProcessState> proc = ProcessState::self();
//启动新binder线程
proc->startThreadPool();
}
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