Android源码之Binder(三)

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{
int ret;
struct binder_proc *proc = filp->private_data;
[// struct binder_proc *proc = filp->private_data
这里获得前面Binder驱动程序为Service Manager进程创建的一个binder_proc结构体。
]// struct binder_proc *proc = filp->private_data
struct binder_thread *thread;
unsigned int size = _IOC_SIZE(cmd);
[// unsigned int size = _IOC_SIZE(cmd)
size表示命令关键字的大小
]// unsigned int size = _IOC_SIZE(cmd)
void __user *ubuf = (void __user *)arg;
[// void __user *ubuf = (void __user *)arg
ubuf指向用户空间的数据起止地址
]// void __user *ubuf = (void __user *)arg

/*printk(KERN_INFO "binder_ioctl: %d:%d %x %lx\n", proc->pid, current->pid, cmd, arg);*/

ret = wait_event_interruptible(binder_user_error_wait, binder_stop_on_user_error < 2);
if (ret)
return ret;

mutex_lock(&binder_lock);
thread = binder_get_thread(proc);
[// thread = binder_get_thread(proc)
这里调用binder_get_thread函数得到进程的一个binder线程。
binder_get_thread函数的定义如下：
static struct binder_thread *binder_get_thread(struct binder_proc *proc)
{
struct binder_thread *thread = NULL;
struct rb_node *parent = NULL;
struct rb_node **p = &proc->threads.rb_node;

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
break;
}
[// while (*p)
上面这段代码是查找是否已经存在该Binder线程
]// while (*p)
if (*p == NULL) {
thread = kzalloc(sizeof(*thread), GFP_KERNEL);
if (thread == NULL)
return NULL;
binder_stats_created(BINDER_STAT_THREAD);
thread->proc = proc;
thread->pid = current->pid;
init_waitqueue_head(&thread->wait);
INIT_LIST_HEAD(&thread->todo);
rb_link_node(&thread->rb_node, parent, p);
rb_insert_color(&thread->rb_node, &proc->threads);
thread->looper |= BINDER_LOOPER_STATE_NEED_RETURN;
thread->return_error = BR_OK;
thread->return_error2 = BR_OK;
}
[// if (*p == NULL)
在这个if语句中，会创建一个binder_thread结构体，并将它插入到binder_proc结构体中去。
]// if (*p == NULL)
return thread;
}
]// thread = binder_get_thread(proc)
if (thread == NULL) {
ret = -ENOMEM;
goto err;
}

switch (cmd) {
case BINDER_WRITE_READ: {
[// case BINDER_WRITE_READ
在这个分支里处理与Binder驱动程序的通信。
]// case BINDER_WRITE_READ
struct binder_write_read bwr;
if (size != sizeof(struct binder_write_read)) {
ret = -EINVAL;
goto err;
}
if (copy_from_user(&bwr, ubuf, sizeof(bwr))) {
ret = -EFAULT;
goto err;
}
[// if (copy_from_user(&bwr, ubuf, sizeof(bwr)))
这里调用copy_from_user将从用户空间传进来的一个binder_write_read结构体拷贝出来，并且保存在变量bwr中。
]// if (copy_from_user(&bwr, ubuf, sizeof(bwr)))

binder_debug(BINDER_DEBUG_READ_WRITE,
"binder: %d:%d write %ld at %08lx, read %ld at %08lx\n",
proc->pid, thread->pid, bwr.write_size, bwr.write_buffer,
bwr.read_size, bwr.read_buffer);

if (bwr.write_size > 0) {
[// if (bwr.write_size > 0)
如果输入缓冲区长度大于0，就会调用binder_thread_write来处理发送给Binder驱动的具体的命令协议
]// if (bwr.write_size > 0)
ret = binder_thread_write(proc, thread, (void __user *)bwr.write_buffer, bwr.write_size, &bwr.write_consumed);
[// ret = binder_thread_write(proc, thread, (void __user *)bwr.write_buffer, bwr.write_size, &bwr.write_consumed)
第一个参数proc表示进程信息
第二个参数thread表示Binder线程信息
第三个参数buffer指向用户空间地址，表示数据缓冲区的开始
第四个参数size表示缓冲区的大小
第五个参数consumed表示已经处理过的偏移
binder_thread_write函数的定义如下：
int binder_thread_write(struct binder_proc *proc, struct binder_thread *thread, void __user *buffer, int size, signed long *consumed)
{
uint32_t cmd;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;

while (ptr < end && thread->return_error == BR_OK) {
[// while (ptr < end && thread->return_error == BR_OK)
在while循环中处理所有的命令请求
]// while (ptr < end && thread->return_error == BR_OK)
if (get_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
[// if (get_user(cmd, (uint32_t __user *)ptr))
这里取出的命令字保存到cmd中
]// if (get_user(cmd, (uint32_t __user *)ptr))
ptr += sizeof(uint32_t);
[// ptr += sizeof(uint32_t)
将数据缓冲区指针移动cmd大小的字节数
]// ptr += sizeof(uint32_t)
if (_IOC_NR(cmd) < ARRAY_SIZE(binder_stats.bc)) {
binder_stats.bc[_IOC_NR(cmd)]++;
proc->stats.bc[_IOC_NR(cmd)]++;
thread->stats.bc[_IOC_NR(cmd)]++;
}
[// if (_IOC_NR(cmd) < ARRAY_SIZE(binder_stats.bc))
这主要是用于统计
]// if (_IOC_NR(cmd) < ARRAY_SIZE(binder_stats.bc))
switch (cmd) {
case BC_INCREFS:
case BC_ACQUIRE:
case BC_RELEASE:
case BC_DECREFS: {
uint32_t target;
struct binder_ref *ref;
const char *debug_string;

if (get_user(target, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (target == 0 && binder_context_mgr_node &&
(cmd == BC_INCREFS || cmd == BC_ACQUIRE)) {
ref = binder_get_ref_for_node(proc,
   binder_context_mgr_node);
if (ref->desc != target) {
binder_user_error("binder: %d:"
"%d tried to acquire "
"reference to desc 0, "
"got %d instead\n",
proc->pid, thread->pid,
ref->desc);
}
} else
ref = binder_get_ref(proc, target);
if (ref == NULL) {
binder_user_error("binder: %d:%d refcou"
"nt change on invalid ref %d\n",
proc->pid, thread->pid, target);
break;
}
switch (cmd) {
case BC_INCREFS:
debug_string = "IncRefs";
binder_inc_ref(ref, 0, NULL);
break;
case BC_ACQUIRE:
debug_string = "Acquire";
binder_inc_ref(ref, 1, NULL);
break;
case BC_RELEASE:
debug_string = "Release";
binder_dec_ref(ref, 1);
break;
case BC_DECREFS:
default:
debug_string = "DecRefs";
binder_dec_ref(ref, 0);
break;
}
binder_debug(BINDER_DEBUG_USER_REFS,
"binder: %d:%d %s ref %d desc %d s %d w %d for node %d\n",
proc->pid, thread->pid, debug_string, ref->debug_id,
ref->desc, ref->strong, ref->weak, ref->node->debug_id);
break;
}
case BC_INCREFS_DONE:
case BC_ACQUIRE_DONE: {
void __user *node_ptr;
void *cookie;
struct binder_node *node;

if (get_user(node_ptr, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);
if (get_user(cookie, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);
node = binder_get_node(proc, node_ptr);
if (node == NULL) {
binder_user_error("binder: %d:%d "
"%s u%p no match\n",
proc->pid, thread->pid,
cmd == BC_INCREFS_DONE ?
"BC_INCREFS_DONE" :
"BC_ACQUIRE_DONE",
node_ptr);
break;
}
if (cookie != node->cookie) {
binder_user_error("binder: %d:%d %s u%p node %d"
" cookie mismatch %p != %p\n",
proc->pid, thread->pid,
cmd == BC_INCREFS_DONE ?
"BC_INCREFS_DONE" : "BC_ACQUIRE_DONE",
node_ptr, node->debug_id,
cookie, node->cookie);
break;
}
if (cmd == BC_ACQUIRE_DONE) {
if (node->pending_strong_ref == 0) {
binder_user_error("binder: %d:%d "
"BC_ACQUIRE_DONE node %d has "
"no pending acquire request\n",
proc->pid, thread->pid,
node->debug_id);
break;
}
node->pending_strong_ref = 0;
} else {
if (node->pending_weak_ref == 0) {
binder_user_error("binder: %d:%d "
"BC_INCREFS_DONE node %d has "
"no pending increfs request\n",
proc->pid, thread->pid,
node->debug_id);
break;
}
node->pending_weak_ref = 0;
}
binder_dec_node(node, cmd == BC_ACQUIRE_DONE, 0);
binder_debug(BINDER_DEBUG_USER_REFS,
"binder: %d:%d %s node %d ls %d lw %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);
break;
}
case BC_ATTEMPT_ACQUIRE:
printk(KERN_ERR "binder: BC_ATTEMPT_ACQUIRE not supported\n");
return -EINVAL;
case BC_ACQUIRE_RESULT:
printk(KERN_ERR "binder: BC_ACQUIRE_RESULT not supported\n");
return -EINVAL;

case BC_FREE_BUFFER: {
void __user *data_ptr;
struct binder_buffer *buffer;

if (get_user(data_ptr, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);

buffer = binder_buffer_lookup(proc, data_ptr);
if (buffer == NULL) {
binder_user_error("binder: %d:%d "
"BC_FREE_BUFFER u%p no match\n",
proc->pid, thread->pid, data_ptr);
break;
}
if (!buffer->allow_user_free) {
binder_user_error("binder: %d:%d "
"BC_FREE_BUFFER u%p matched "
"unreturned buffer\n",
proc->pid, thread->pid, data_ptr);
break;
}
binder_debug(BINDER_DEBUG_FREE_BUFFER,
"binder: %d:%d BC_FREE_BUFFER u%p found buffer %d for %s transaction\n",
proc->pid, thread->pid, 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) {
BUG_ON(!buffer->target_node->has_async_transaction);
if (list_empty(&buffer->target_node->async_todo))
buffer->target_node->has_async_transaction = 0;
else
list_move_tail(buffer->target_node->async_todo.next, &thread->todo);
}
binder_transaction_buffer_release(proc, buffer, NULL);
binder_free_buf(proc, buffer);
break;
}

case BC_TRANSACTION:
case BC_REPLY: {
[// case BC_REPLY
BC_TRANSACTION和BC_REPLY就是处理用户Client组件和Service组件通信的命令
]// 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);
[// binder_transaction(proc, thread, &tr, cmd == BC_REPLY)
binder_transaction函数的定义如下：
static void binder_transaction(struct binder_proc *proc,
   struct binder_thread *thread,
   struct binder_transaction_data *tr, int reply)
{
struct binder_transaction *t;
struct binder_work *tcomplete;
size_t *offp, *off_end;
struct binder_proc *target_proc;
struct binder_thread *target_thread = NULL;
struct binder_node *target_node = NULL;
struct list_head *target_list;
wait_queue_head_t *target_wait;
struct binder_transaction *in_reply_to = NULL;
struct binder_transaction_log_entry *e;
uint32_t return_error;

e = binder_transaction_log_add(&binder_transaction_log);
e->call_type = reply ? 2 : !!(tr->flags & TF_ONE_WAY);
e->from_proc = proc->pid;
e->from_thread = thread->pid;
e->target_handle = tr->target.handle;
e->data_size = tr->data_size;
e->offsets_size = tr->offsets_size;

if (reply) {
[// if (reply)
参数reply的值为cmd == BC_REPLY， 因此reply为0表示处理BC_TRANSACTION, 为1表示处理BC_REPLY
]// if (reply)
in_reply_to = thread->transaction_stack;
if (in_reply_to == NULL) {
binder_user_error("binder: %d:%d got reply transaction "
  "with no transaction stack\n",
  proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_empty_call_stack;
}
binder_set_nice(in_reply_to->saved_priority);
if (in_reply_to->to_thread != thread) {
binder_user_error("binder: %d:%d got reply transaction "
"with bad transaction stack,"
" transaction %d has target %d:%d\n",
proc->pid, thread->pid, in_reply_to->debug_id,
in_reply_to->to_proc ?
in_reply_to->to_proc->pid : 0,
in_reply_to->to_thread ?
in_reply_to->to_thread->pid : 0);
return_error = BR_FAILED_REPLY;
in_reply_to = NULL;
goto err_bad_call_stack;
}
thread->transaction_stack = in_reply_to->to_parent;
target_thread = in_reply_to->from;
if (target_thread == NULL) {
return_error = BR_DEAD_REPLY;
goto err_dead_binder;
}
if (target_thread->transaction_stack != in_reply_to) {
binder_user_error("binder: %d:%d got reply transaction "
"with bad target transaction stack %d, "
"expected %d\n",
proc->pid, thread->pid,
target_thread->transaction_stack ?
target_thread->transaction_stack->debug_id : 0,
in_reply_to->debug_id);
return_error = BR_FAILED_REPLY;
in_reply_to = NULL;
target_thread = NULL;
goto err_dead_binder;
}
target_proc = target_thread->proc;
} else {
[// else {
在这个else分支中处理BC_TRANSACTION的命令字
]// else {
if (tr->target.handle) {
struct binder_ref *ref;
ref = binder_get_ref(proc, tr->target.handle);
[// ref = binder_get_ref(proc, tr->target.handle)
调用binder_get_ref来查找Binder引用对象
]// ref = binder_get_ref(proc, tr->target.handle)
if (ref == NULL) {
binder_user_error("binder: %d:%d got "
"transaction to invalid handle\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_invalid_target_handle;
}
target_node = ref->node;
[// target_node = ref->node
当查找到Binder引用对象之后，就根据该Binder引用对象找到对应的Binder实体对象，并赋值给target_node
]// target_node = ref->node
} else {
target_node = binder_context_mgr_node;
[// target_node = binder_context_mgr_node
这里target_node指向ServiceManager的Binder实体对象，因为tr->target.handle为0，表示请求ServiceManager来处理
]// target_node = binder_context_mgr_node
if (target_node == NULL) {
return_error = BR_DEAD_REPLY;
goto err_no_context_mgr_node;
}
}
e->to_node = target_node->debug_id;
target_proc = target_node->proc;
if (target_proc == NULL) {
return_error = BR_DEAD_REPLY;
goto err_dead_binder;
}
if (!(tr->flags & TF_ONE_WAY) && thread->transaction_stack) {
struct binder_transaction *tmp;
tmp = thread->transaction_stack;
if (tmp->to_thread != thread) {
binder_user_error("binder: %d:%d got new "
"transaction with bad transaction stack"
", transaction %d has target %d:%d\n",
proc->pid, thread->pid, tmp->debug_id,
tmp->to_proc ? tmp->to_proc->pid : 0,
tmp->to_thread ?
tmp->to_thread->pid : 0);
return_error = BR_FAILED_REPLY;
goto err_bad_call_stack;
}
while (tmp) {
if (tmp->from && tmp->from->proc == target_proc)
target_thread = tmp->from;
tmp = tmp->from_parent;
}
}
}
if (target_thread) {
[// if (target_thread)
target_thread指向要处理请求Binder线程
]// if (target_thread)
e->to_thread = target_thread->pid;
target_list = &target_thread->todo;
target_wait = &target_thread->wait;
} else {
target_list = &target_proc->todo;
target_wait = &target_proc->wait;
}
e->to_proc = target_proc->pid;

/* TODO: reuse incoming transaction for reply */
t = kzalloc(sizeof(*t), GFP_KERNEL);
[// t = kzalloc(sizeof(*t), GFP_KERNEL)
这里申请一个binder_transaction结构体，以便后面会将它封装为一个BINDER_WORK_TRANSACTION类型的工作项加入到目标todo队列target_list中，以便目标线程可以接收到一个BR_TRANSACTION返回协议。
]// t = kzalloc(sizeof(*t), GFP_KERNEL)
if (t == NULL) {
return_error = BR_FAILED_REPLY;
goto err_alloc_t_failed;
}
binder_stats_created(BINDER_STAT_TRANSACTION);

tcomplete = kzalloc(sizeof(*tcomplete), GFP_KERNEL);
if (tcomplete == NULL) {
return_error = BR_FAILED_REPLY;
goto err_alloc_tcomplete_failed;
}
binder_stats_created(BINDER_STAT_TRANSACTION_COMPLETE);

t->debug_id = ++binder_last_id;
e->debug_id = t->debug_id;

if (reply)
binder_debug(BINDER_DEBUG_TRANSACTION,
"binder: %d:%d BC_REPLY %d -> %d:%d, "
"data %p-%p size %zd-%zd\n",
proc->pid, thread->pid, t->debug_id,
target_proc->pid, target_thread->pid,
tr->data.ptr.buffer, tr->data.ptr.offsets,
tr->data_size, tr->offsets_size);
else
binder_debug(BINDER_DEBUG_TRANSACTION,
"binder: %d:%d BC_TRANSACTION %d -> "
"%d - node %d, data %p-%p size %zd-%zd\n",
proc->pid, thread->pid, t->debug_id,
target_proc->pid, target_node->debug_id,
tr->data.ptr.buffer, tr->data.ptr.offsets,
tr->data_size, tr->offsets_size);

if (!reply && !(tr->flags & TF_ONE_WAY))
t->from = thread;
else
t->from = NULL;
t->sender_euid = proc->tsk->cred->euid;
t->to_proc = target_proc;
t->to_thread = target_thread;
t->code = tr->code;
t->flags = tr->flags;
t->priority = task_nice(current);
t->buffer = binder_alloc_buf(target_proc, tr->data_size,
tr->offsets_size, !reply && (t->flags & TF_ONE_WAY));
[// t->buffer = binder_alloc_buf
这里为binder_transaction结构体t分配一个内核缓冲区，以便可以将进程间通信数据拷贝到它里面，最后传递给目标进程target_proc或者目标线程target_thread处理。注意这个内核缓冲区是在目标进程target_proc中分配的。
]// t->buffer = binder_alloc_buf
if (t->buffer == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_alloc_buf_failed;
}
t->buffer->allow_user_free = 0;
t->buffer->debug_id = t->debug_id;
t->buffer->transaction = t;
t->buffer->target_node = target_node;
if (target_node)
binder_inc_node(target_node, 1, 0, NULL);

offp = (size_t *)(t->buffer->data + ALIGN(tr->data_size, sizeof(void *)));

if (copy_from_user(t->buffer->data, tr->data.ptr.buffer, tr->data_size)) {
[// if (copy_from_user(t->buffer->data, tr->data.ptr.buffer, tr->data_size))
这里将binder_transaction_data结构体tr的数据缓冲区，以及偏移数组的内容拷贝到分配给binder_transaction结构体tr的内核缓冲区
]// if (copy_from_user(t->buffer->data, tr->data.ptr.buffer, tr->data_size))
binder_user_error("binder: %d:%d got transaction with invalid "
"data ptr\n", proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_copy_data_failed;
}

if (copy_from_user(offp, tr->data.ptr.offsets, tr->offsets_size)) {
[// if (copy_from_user(offp, tr->data.ptr.offsets, tr->offsets_size))
这里计算分配给binder_transaction结构体t的内核缓冲区中用来保存偏移数组的开始位置offp
]// if (copy_from_user(offp, tr->data.ptr.offsets, tr->offsets_size))
binder_user_error("binder: %d:%d got transaction with invalid "
"offsets ptr\n", proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_copy_data_failed;
}
if (!IS_ALIGNED(tr->offsets_size, sizeof(size_t))) {
binder_user_error("binder: %d:%d got transaction with "
"invalid offsets size, %zd\n",
proc->pid, thread->pid, tr->offsets_size);
return_error = BR_FAILED_REPLY;
goto err_bad_offset;
}
off_end = (void *)offp + tr->offsets_size;
[// off_end = (void *)offp + tr->offsets_size
这里计算分配给binder_transaction结构体t的内核缓冲区中用来保存偏移数组的结束位置off_end
]// off_end = (void *)offp + tr->offsets_size
for (; offp < off_end; offp++) {
[// for (; offp < off_end; offp++)
函数接下来就在这个for循环中依次处理进程间通信数据中的Binder对象。
]// for (; offp < off_end; offp++)
struct flat_binder_object *fp;
if (*offp > t->buffer->data_size - sizeof(*fp) ||
t->buffer->data_size < sizeof(*fp) ||
!IS_ALIGNED(*offp, sizeof(void *))) {
binder_user_error("binder: %d:%d got transaction with "
"invalid offset, %zd\n",
proc->pid, thread->pid, *offp);
return_error = BR_FAILED_REPLY;
goto err_bad_offset;
}
fp = (struct flat_binder_object *)(t->buffer->data + *offp);
switch (fp->type) {
case BINDER_TYPE_BINDER:
case BINDER_TYPE_WEAK_BINDER: {
struct binder_ref *ref;
struct binder_node *node = binder_get_node(proc, fp->binder);
if (node == NULL) {
node = binder_new_node(proc, fp->binder, fp->cookie);
[// node = binder_new_node(proc, fp->binder, fp->cookie)
这里是在本进程中查找该Binder实体对象，如果没有就会创建该Binder实体对象
]// node = binder_new_node(proc, fp->binder, fp->cookie)
if (node == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_new_node_failed;
}
node->min_priority = fp->flags & FLAT_BINDER_FLAG_PRIORITY_MASK;
node->accept_fds = !!(fp->flags & FLAT_BINDER_FLAG_ACCEPTS_FDS);
}
if (fp->cookie != node->cookie) {
binder_user_error("binder: %d:%d sending u%p "
"node %d, cookie mismatch %p != %p\n",
proc->pid, thread->pid,
fp->binder, node->debug_id,
fp->cookie, node->cookie);
goto err_binder_get_ref_for_node_failed;
}
ref = binder_get_ref_for_node(target_proc, node);
[// ref = binder_get_ref_for_node(target_proc, node)
这里会在目标进程中创建一个Binder引用对象。
binder_get_ref_for_node的函数实现如下：
static struct binder_ref *binder_get_ref_for_node(struct binder_proc *proc, struct binder_node *node)
{
struct rb_node *n;
struct rb_node **p = &proc->refs_by_node.rb_node;
struct rb_node *parent = NULL;
struct binder_ref *ref, *new_ref;

while (*p) {
parent = *p;
ref = rb_entry(parent, struct binder_ref, rb_node_node);

if (node < ref->node)
p = &(*p)->rb_left;
else if (node > ref->node)
p = &(*p)->rb_right;
else
return ref;
}
new_ref = kzalloc(sizeof(*ref), GFP_KERNEL);
if (new_ref == NULL)
return NULL;
binder_stats_created(BINDER_STAT_REF);
new_ref->debug_id = ++binder_last_id;
new_ref->proc = proc;
new_ref->node = node;
rb_link_node(&new_ref->rb_node_node, parent, p);
rb_insert_color(&new_ref->rb_node_node, &proc->refs_by_node);

new_ref->desc = (node == binder_context_mgr_node) ? 0 : 1;
for (n = rb_first(&proc->refs_by_desc); n != NULL; n = rb_next(n)) {
ref = rb_entry(n, struct binder_ref, rb_node_desc);
if (ref->desc > new_ref->desc)
break;
new_ref->desc = ref->desc + 1;
}

p = &proc->refs_by_desc.rb_node;
while (*p) {
parent = *p;
ref = rb_entry(parent, struct binder_ref, rb_node_desc);

if (new_ref->desc < ref->desc)
p = &(*p)->rb_left;
else if (new_ref->desc > ref->desc)
p = &(*p)->rb_right;
else
BUG();
}
rb_link_node(&new_ref->rb_node_desc, parent, p);
rb_insert_color(&new_ref->rb_node_desc, &proc->refs_by_desc);
if (node) {
hlist_add_head(&new_ref->node_entry, &node->refs);
[// hlist_add_head(&new_ref->node_entry, &node->refs)
这里将刚刚创建的Binder引用对象添加到它所引用的Binder实体对象的Binder引用对象列表中
]// hlist_add_head(&new_ref->node_entry, &node->refs)

binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"binder: %d new ref %d desc %d for "
"node %d\n", proc->pid, new_ref->debug_id,
new_ref->desc, node->debug_id);
} else {
binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"binder: %d new ref %d desc %d for "
"dead node\n", proc->pid, new_ref->debug_id,
  new_ref->desc);
}
return new_ref;
}
]// ref = binder_get_ref_for_node(target_proc, node)
if (ref == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_get_ref_for_node_failed;
}
if (fp->type == BINDER_TYPE_BINDER)
fp->type = BINDER_TYPE_HANDLE;
else
fp->type = BINDER_TYPE_WEAK_HANDLE;
fp->handle = ref->desc;
binder_inc_ref(ref, fp->type == BINDER_TYPE_HANDLE,
   &thread->todo);

binder_debug(BINDER_DEBUG_TRANSACTION,
"        node %d u%p -> ref %d desc %d\n",
node->debug_id, node->ptr, ref->debug_id,
ref->desc);
} break;
case BINDER_TYPE_HANDLE:
case BINDER_TYPE_WEAK_HANDLE: {
struct binder_ref *ref = binder_get_ref(proc, fp->handle);
if (ref == NULL) {
binder_user_error("binder: %d:%d got "
"transaction with invalid "
"handle, %ld\n", proc->pid,
thread->pid, fp->handle);
return_error = BR_FAILED_REPLY;
goto err_binder_get_ref_failed;
}
if (ref->node->proc == target_proc) {
if (fp->type == BINDER_TYPE_HANDLE)
fp->type = BINDER_TYPE_BINDER;
else
fp->type = BINDER_TYPE_WEAK_BINDER;
fp->binder = ref->node->ptr;
fp->cookie = ref->node->cookie;
binder_inc_node(ref->node, fp->type == BINDER_TYPE_BINDER, 0, NULL);
binder_debug(BINDER_DEBUG_TRANSACTION,
"        ref %d desc %d -> node %d u%p\n",
ref->debug_id, ref->desc, ref->node->debug_id,
ref->node->ptr);
} else {
struct binder_ref *new_ref;
new_ref = binder_get_ref_for_node(target_proc, ref->node);
if (new_ref == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_get_ref_for_node_failed;
}
fp->handle = new_ref->desc;
binder_inc_ref(new_ref, fp->type == BINDER_TYPE_HANDLE, NULL);
binder_debug(BINDER_DEBUG_TRANSACTION,
"        ref %d desc %d -> ref %d desc %d (node %d)\n",
ref->debug_id, ref->desc, new_ref->debug_id,
new_ref->desc, ref->node->debug_id);
}
} break;

case BINDER_TYPE_FD: {
int target_fd;
struct file *file;

if (reply) {
if (!(in_reply_to->flags & TF_ACCEPT_FDS)) {
binder_user_error("binder: %d:%d got reply with fd, %ld, but target does not allow fds\n",
proc->pid, thread->pid, fp->handle);
return_error = BR_FAILED_REPLY;
goto err_fd_not_allowed;
}
} else if (!target_node->accept_fds) {
binder_user_error("binder: %d:%d got transaction with fd, %ld, but target does not allow fds\n",
proc->pid, thread->pid, fp->handle);
return_error = BR_FAILED_REPLY;
goto err_fd_not_allowed;
}

file = fget(fp->handle);
if (file == NULL) {
binder_user_error("binder: %d:%d got transaction with invalid fd, %ld\n",
proc->pid, thread->pid, fp->handle);
return_error = BR_FAILED_REPLY;
goto err_fget_failed;
}
target_fd = task_get_unused_fd_flags(target_proc, O_CLOEXEC);
if (target_fd < 0) {
fput(file);
return_error = BR_FAILED_REPLY;
goto err_get_unused_fd_failed;
}
task_fd_install(target_proc, target_fd, file);
binder_debug(BINDER_DEBUG_TRANSACTION,
"        fd %ld -> %d\n", fp->handle, target_fd);
/* TODO: fput? */
fp->handle = target_fd;
} break;

default:
binder_user_error("binder: %d:%d got transactio"
"n with invalid object type, %lx\n",
proc->pid, thread->pid, fp->type);
return_error = BR_FAILED_REPLY;
goto err_bad_object_type;
}
}
if (reply) {
BUG_ON(t->buffer->async_transaction != 0);
binder_pop_transaction(target_thread, in_reply_to);
} else if (!(t->flags & TF_ONE_WAY)) {
BUG_ON(t->buffer->async_transaction != 0);
t->need_reply = 1;
t->from_parent = thread->transaction_stack;
thread->transaction_stack = t;
} else {
BUG_ON(target_node == NULL);
BUG_ON(t->buffer->async_transaction != 1);
if (target_node->has_async_transaction) {
target_list = &target_node->async_todo;
target_wait = NULL;
} else
target_node->has_async_transaction = 1;
}
t->work.type = BINDER_WORK_TRANSACTION;
list_add_tail(&t->work.entry, target_list);
tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE;
list_add_tail(&tcomplete->entry, &thread->todo);
if (target_wait)
wake_up_interruptible(target_wait);
[// if (target_wait)
上面这几句代码就是将工作项添加到目标进程target_proc或者目标线程target_thread的todo队列中，并唤醒目标进程target_proc或者目标线程target_thread。
]// if (target_wait)
return;

err_get_unused_fd_failed:
err_fget_failed:
err_fd_not_allowed:
err_binder_get_ref_for_node_failed:
err_binder_get_ref_failed:
err_binder_new_node_failed:
err_bad_object_type:
err_bad_offset:
err_copy_data_failed:
binder_transaction_buffer_release(target_proc, t->buffer, offp);
t->buffer->transaction = NULL;
binder_free_buf(target_proc, t->buffer);
err_binder_alloc_buf_failed:
kfree(tcomplete);
binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
err_alloc_tcomplete_failed:
kfree(t);
binder_stats_deleted(BINDER_STAT_TRANSACTION);
err_alloc_t_failed:
err_bad_call_stack:
err_empty_call_stack:
err_dead_binder:
err_invalid_target_handle:
err_no_context_mgr_node:
binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
"binder: %d:%d transaction failed %d, size %zd-%zd\n",
proc->pid, thread->pid, return_error,
tr->data_size, tr->offsets_size);

{
struct binder_transaction_log_entry *fe;
fe = binder_transaction_log_add(&binder_transaction_log_failed);
*fe = *e;
}

BUG_ON(thread->return_error != BR_OK);
if (in_reply_to) {
thread->return_error = BR_TRANSACTION_COMPLETE;
binder_send_failed_reply(in_reply_to, return_error);
} else
thread->return_error = return_error;
}
]// binder_transaction(proc, thread, &tr, cmd == BC_REPLY)
break;
}

case BC_REGISTER_LOOPER:
binder_debug(BINDER_DEBUG_THREADS,
"binder: %d:%d BC_REGISTER_LOOPER\n",
proc->pid, thread->pid);
if (thread->looper & BINDER_LOOPER_STATE_ENTERED) {
thread->looper |= BINDER_LOOPER_STATE_INVALID;
binder_user_error("binder: %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("binder: %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;
break;
case BC_ENTER_LOOPER:
[// case BC_ENTER_LOOPER
BC_ENTER_LOOPER命令字是为了通知Binder驱动程序，Binder线程已经准备就绪处理进程间通信请求了。
]// case BC_ENTER_LOOPER
binder_debug(BINDER_DEBUG_THREADS,
"binder: %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("binder: %d:%d ERROR:"
" BC_ENTER_LOOPER called after "
"BC_REGISTER_LOOPER\n",
proc->pid, thread->pid);
}
thread->looper |= BINDER_LOOPER_STATE_ENTERED;
[// thread->looper |= BINDER_LOOPER_STATE_ENTERED
将目标线程thread的状态设置为BINDER_LOOPER_STATE_ENTERED，表明该Binder线程可以处理进程间通信请求。
]// thread->looper |= BINDER_LOOPER_STATE_ENTERED
break;
case BC_EXIT_LOOPER:
binder_debug(BINDER_DEBUG_THREADS,
"binder: %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;
void __user *cookie;
struct binder_ref *ref;
struct binder_ref_death *death;

if (get_user(target, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (get_user(cookie, (void __user * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);
ref = binder_get_ref(proc, target);
if (ref == NULL) {
binder_user_error("binder: %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);
break;
}

binder_debug(BINDER_DEBUG_DEATH_NOTIFICATION,
"binder: %d:%d %s %p 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",
cookie, ref->debug_id, ref->desc,
ref->strong, ref->weak, ref->node->debug_id);

if (cmd == BC_REQUEST_DEATH_NOTIFICATION) {
if (ref->death) {
binder_user_error("binder: %d:%"
"d BC_REQUEST_DEATH_NOTI"
"FICATION death notific"
"ation already set\n",
proc->pid, thread->pid);
break;
}
death = kzalloc(sizeof(*death), GFP_KERNEL);
if (death == NULL) {
thread->return_error = BR_ERROR;
binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
"binder: %d:%d "
"BC_REQUEST_DEATH_NOTIFICATION failed\n",
proc->pid, thread->pid);
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;
if (thread->looper & (BINDER_LOOPER_STATE_REGISTERED | BINDER_LOOPER_STATE_ENTERED)) {
list_add_tail(&ref->death->work.entry, &thread->todo);
} else {
list_add_tail(&ref->death->work.entry, &proc->todo);
wake_up_interruptible(&proc->wait);
}
}
} else {
if (ref->death == NULL) {
binder_user_error("binder: %d:%"
"d BC_CLEAR_DEATH_NOTIFI"
"CATION death notificat"
"ion not active\n",
proc->pid, thread->pid);
break;
}
death = ref->death;
if (death->cookie != cookie) {
binder_user_error("binder: %d:%"
"d BC_CLEAR_DEATH_NOTIFI"
"CATION death notificat"
"ion cookie mismatch "
"%p != %p\n",
proc->pid, thread->pid,
death->cookie, cookie);
break;
}
ref->death = NULL;
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)) {
list_add_tail(&death->work.entry, &thread->todo);
} else {
list_add_tail(&death->work.entry, &proc->todo);
wake_up_interruptible(&proc->wait);
}
} else {
BUG_ON(death->work.type != BINDER_WORK_DEAD_BINDER);
death->work.type = BINDER_WORK_DEAD_BINDER_AND_CLEAR;
}
}
} break;
case BC_DEAD_BINDER_DONE: {
struct binder_work *w;
void __user *cookie;
struct binder_ref_death *death = NULL;
if (get_user(cookie, (void __user * __user *)ptr))
return -EFAULT;

ptr += sizeof(void *);
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,
"binder: %d:%d BC_DEAD_BINDER_DONE %p found %p\n",
proc->pid, thread->pid, cookie, death);
if (death == NULL) {
binder_user_error("binder: %d:%d BC_DEAD"
"_BINDER_DONE %p not found\n",
proc->pid, thread->pid, cookie);
break;
}

list_del_init(&death->work.entry);
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)) {
list_add_tail(&death->work.entry, &thread->todo);
} else {
list_add_tail(&death->work.entry, &proc->todo);
wake_up_interruptible(&proc->wait);
}
}
} break;

default:
printk(KERN_ERR "binder: %d:%d unknown command %d\n",
   proc->pid, thread->pid, cmd);
return -EINVAL;
}
*consumed = ptr - buffer;
[// *consumed = ptr - buffer
这里更新已经处理的大小
]// *consumed = ptr - buffer
}
return 0;
}

] //ret = binder_thread_write(proc, thread, (void __user *)bwr.write_buffer, bwr.write_size, &bwr.write_consumed)
if (ret < 0) {
bwr.read_consumed = 0;
if (copy_to_user(ubuf, &bwr, sizeof(bwr)))
ret = -EFAULT;
goto err;
}
}

if (bwr.read_size > 0) {
[// if (bwr.read_size > 0)
如果输出缓冲区长度大于0, binder_thread_read将Binder驱动程序的结果返回给Client组件去处理。
]// if (bwr.read_size > 0)
ret = binder_thread_read(proc, thread, (void __user *)bwr.read_buffer, bwr.read_size, &bwr.read_consumed, filp->f_flags & O_NONBLOCK);
[// ret = binder_thread_read(proc, thread, (void __user *)bwr.read_buffer, bwr.read_size, &bwr.read_consumed, filp->f_flags & O_NONBLOCK)
binder_thread_read函数的定义如下：
第一个参数proc表示进程信息
第二个参数thread表示Binder线程信息
第三个参数buffer指向用户空间地址，表示数据缓冲区的开始
第四个参数size表示缓冲区的大小
第五个参数consumed表示已经处理过的偏移
第六个参数non_block表示当前线程是否以非阻塞模式打开设备文件/dev/binder，如果是，就表示当前线程不可以在Binder驱动程序中睡眠，即如果当前线程发现其所属进程的todo队列为空时，它不可以进入睡眠状态去等待该进程有新的未处理工作项。
static int binder_thread_read(struct binder_proc *proc, struct binder_thread *thread, void  __user *buffer, int size, signed long *consumed, int non_block)
{
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);
}
[// if (*consumed == 0)
这为什么要发送一个BR_NOOP命令字??????????
]// if (*consumed == 0)

retry:
wait_for_proc_work = thread->transaction_stack == NULL && list_empty(&thread->todo);
[// wait_for_proc_work = thread->transaction_stack == NULL && list_empty(&thread->todo)
wait_for_proc_work表示线程是否可以处理进程的工作项。
如果一个线程的事务堆栈thread->transaction_stack不等于NULL, 就表示它正在等待其他线程完成另外一个事务。
如果一个线程的todo队列不为空，就说明该线程有未处理的工作项。
一个线程只有在其事务堆栈transaction_stack为NULL，并且其todo队列为空时，才可以去处理其所属进程的todo队列中的待处理工作项。
因此，这里当thread->transaction_stack == NULL并且线程的todo队列为空时，wait_for_proc_work值为1。有一个条件不满足时，wait_for_proc_work的值为0.
]// wait_for_proc_work = thread->transaction_stack == NULL && list_empty(&thread->todo)

if (thread->return_error != BR_OK && ptr < end) {
if (thread->return_error2 != BR_OK) {
if (put_user(thread->return_error2, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (ptr == end)
goto done;
thread->return_error2 = BR_OK;
}
if (put_user(thread->return_error, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
thread->return_error = BR_OK;
goto done;
}
[// if (thread->return_error != BR_OK && ptr < end)
这个if语句是发现错误。如果发现错误，则传给应用层。
]// if (thread->return_error != BR_OK && ptr < end)


thread->looper |= BINDER_LOOPER_STATE_WAITING;
[// thread->looper |= BINDER_LOOPER_STATE_WAITING
这里将线程的状态设置为BINDER_LOOPER_STATE_WAITING，表示就绪状态
]// thread->looper |= BINDER_LOOPER_STATE_WAITING
if (wait_for_proc_work)
proc->ready_threads++;
[// if (wait_for_proc_work)
wait_for_proc_work为1，表示线程可以去处理进程的任务，因此这里将进程的ready_threads的值增加1，表示线程又多了一个空闲线程
]// if (wait_for_proc_work)
mutex_unlock(&binder_lock);
if (wait_for_proc_work) {
if (!(thread->looper & (BINDER_LOOPER_STATE_REGISTERED |
BINDER_LOOPER_STATE_ENTERED))) {
binder_user_error("binder: %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_set_nice(proc->default_priority);
[// binder_set_nice(proc->default_priority)
这里将线程的nice值设置为进程的nice值，因为线程要代替进程去完成工作任务。
binder_set_nice的函数定义如下：
static void binder_set_nice(long nice)
{
long min_nice;
if (can_nice(current, nice)) {
set_user_nice(current, nice);
return;
}
min_nice = 20 - current->signal->rlim[RLIMIT_NICE].rlim_cur;
binder_debug(BINDER_DEBUG_PRIORITY_CAP,
"binder: %d: nice value %ld not allowed use "
"%ld instead\n", current->pid, nice, min_nice);
set_user_nice(current, min_nice);
if (min_nice < 20)
return;
binder_user_error("binder: %d RLIMIT_NICE not set\n", current->pid);
}
]// binder_set_nice(proc->default_priority)
if (non_block) {
if (!binder_has_proc_work(proc, thread))
[// if (!binder_has_proc_work(proc, thread))
binder_has_proc_work函数判断进程是否有要处理的工作
static int binder_has_proc_work(struct binder_proc *proc, struct binder_thread *thread)
{
return !list_empty(&proc->todo) || (thread->looper & BINDER_LOOPER_STATE_NEED_RETURN);
}
]// if (!binder_has_proc_work(proc, thread))
ret = -EAGAIN;
} else
ret = wait_event_interruptible_exclusive(proc->wait, binder_has_proc_work(proc, thread));
[// if (non_block)
如果non_block为1，则判断进程是否有要处理的任务，如果没有则直接返回到用户空间去了，否则，则等待在进程的wait上去。
]// if (non_block)
} else {
if (non_block) {
if (!binder_has_thread_work(thread))
[// if (!binder_has_thread_work(thread))
binder_has_thread_work函数判断线程是否有要处理的工作
static int binder_has_thread_work(struct binder_thread *thread)
{
return !list_empty(&thread->todo) || thread->return_error != BR_OK ||
(thread->looper & BINDER_LOOPER_STATE_NEED_RETURN);
}
]// if (!binder_has_thread_work(thread))
ret = -EAGAIN;
} else
ret = wait_event_interruptible(thread->wait, binder_has_thread_work(thread));
[// if (non_block)
如果non_block为1，则判断线程是否有要处理的任务，如果没有则直接返回到用户空间去了，否则，则等待在线程的wait上去。
]// if (non_block)
}
mutex_lock(&binder_lock);
if (wait_for_proc_work)
proc->ready_threads--;
[// if (wait_for_proc_work)
这里将进程的ready_threads减1，因为这个线程要去处理任务了
]// if (wait_for_proc_work)
thread->looper &= ~BINDER_LOOPER_STATE_WAITING;
[// thread->looper &= ~BINDER_LOOPER_STATE_WAITING
这里清空线程的BINDER_LOOPER_STATE_WAITING字段，表示该线有任务在身
]// thread->looper &= ~BINDER_LOOPER_STATE_WAITING

if (ret)
return ret;
[// if (ret)
如果ret不为0，则直接返回到用户空间
]// if (ret)

while (1) {
uint32_t cmd;
struct binder_transaction_data tr;
struct binder_work *w;
struct binder_transaction *t = NULL;

if (!list_empty(&thread->todo))
w = list_first_entry(&thread->todo, struct binder_work, entry);
else if (!list_empty(&proc->todo) && wait_for_proc_work)
w = list_first_entry(&proc->todo, struct binder_work, entry);
else {
if (ptr - buffer == 4 && !(thread->looper & BINDER_LOOPER_STATE_NEED_RETURN)) /* no data added */
goto retry;
break;
}

if (end - ptr < sizeof(tr) + 4)
break;

switch (w->type) {
case BINDER_WORK_TRANSACTION: {
t = container_of(w, struct binder_transaction, work);
} break;
case BINDER_WORK_TRANSACTION_COMPLETE: {
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,
"binder: %d:%d BR_TRANSACTION_COMPLETE\n",
proc->pid, thread->pid);

list_del(&w->entry);
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);
uint32_t cmd = BR_NOOP;
const char *cmd_name;
int strong = node->internal_strong_refs || node->local_strong_refs;
int weak = !hlist_empty(&node->refs) || node->local_weak_refs || strong;
if (weak && !node->has_weak_ref) {
cmd = BR_INCREFS;
cmd_name = "BR_INCREFS";
node->has_weak_ref = 1;
node->pending_weak_ref = 1;
node->local_weak_refs++;
} else if (strong && !node->has_strong_ref) {
cmd = BR_ACQUIRE;
cmd_name = "BR_ACQUIRE";
node->has_strong_ref = 1;
node->pending_strong_ref = 1;
node->local_strong_refs++;
} else if (!strong && node->has_strong_ref) {
cmd = BR_RELEASE;
cmd_name = "BR_RELEASE";
node->has_strong_ref = 0;
} else if (!weak && node->has_weak_ref) {
cmd = BR_DECREFS;
cmd_name = "BR_DECREFS";
node->has_weak_ref = 0;
}
if (cmd != BR_NOOP) {
if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (put_user(node->ptr, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);
if (put_user(node->cookie, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);

binder_stat_br(proc, thread, cmd);
binder_debug(BINDER_DEBUG_USER_REFS,
"binder: %d:%d %s %d u%p c%p\n",
proc->pid, thread->pid, cmd_name, node->debug_id, node->ptr, node->cookie);
} else {
list_del_init(&w->entry);
if (!weak && !strong) {
binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"binder: %d:%d node %d u%p c%p deleted\n",
proc->pid, thread->pid, node->debug_id,
node->ptr, node->cookie);
rb_erase(&node->rb_node, &proc->nodes);
kfree(node);
binder_stats_deleted(BINDER_STAT_NODE);
} else {
binder_debug(BINDER_DEBUG_INTERNAL_REFS,
"binder: %d:%d node %d u%p c%p state unchanged\n",
proc->pid, thread->pid, node->debug_id, node->ptr,
node->cookie);
}
}
} 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;

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;
if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (put_user(death->cookie, (void * __user *)ptr))
return -EFAULT;
ptr += sizeof(void *);
binder_debug(BINDER_DEBUG_DEATH_NOTIFICATION,
"binder: %d:%d %s %p\n",
  proc->pid, thread->pid,
  cmd == BR_DEAD_BINDER ?
  "BR_DEAD_BINDER" :
  "BR_CLEAR_DEATH_NOTIFICATION_DONE",
  death->cookie);

if (w->type == BINDER_WORK_CLEAR_DEATH_NOTIFICATION) {
list_del(&w->entry);
kfree(death);
binder_stats_deleted(BINDER_STAT_DEATH);
} else
list_move(&w->entry, &proc->delivered_death);
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;
tr.target.ptr = target_node->ptr;
tr.cookie =  target_node->cookie;
t->saved_priority = task_nice(current);
if (t->priority < target_node->min_priority &&
!(t->flags & TF_ONE_WAY))
binder_set_nice(t->priority);
else if (!(t->flags & TF_ONE_WAY) ||
t->saved_priority > target_node->min_priority)
binder_set_nice(target_node->min_priority);
cmd = BR_TRANSACTION;
} else {
tr.target.ptr = NULL;
tr.cookie = NULL;
cmd = BR_REPLY;
}
tr.code = t->code;
tr.flags = t->flags;
tr.sender_euid = t->sender_euid;

if (t->from) {
struct task_struct *sender = t->from->proc->tsk;
tr.sender_pid = task_tgid_nr_ns(sender,
current->nsproxy->pid_ns);
} else {
tr.sender_pid = 0;
}

tr.data_size = t->buffer->data_size;
tr.offsets_size = t->buffer->offsets_size;
tr.data.ptr.buffer = (void *)t->buffer->data +
proc->user_buffer_offset;
tr.data.ptr.offsets = tr.data.ptr.buffer +
ALIGN(t->buffer->data_size,
sizeof(void *));

if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
if (copy_to_user(ptr, &tr, sizeof(tr)))
return -EFAULT;
ptr += sizeof(tr);

binder_stat_br(proc, thread, cmd);
binder_debug(BINDER_DEBUG_TRANSACTION,
"binder: %d:%d %s %d %d:%d, cmd %d"
"size %zd-%zd ptr %p-%p\n",
proc->pid, thread->pid,
(cmd == BR_TRANSACTION) ? "BR_TRANSACTION" :
"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,
tr.data.ptr.buffer, tr.data.ptr.offsets);

list_del(&t->work.entry);
t->buffer->allow_user_free = 1;
if (cmd == BR_TRANSACTION && !(t->flags & TF_ONE_WAY)) {
t->to_parent = thread->transaction_stack;
t->to_thread = thread;
thread->transaction_stack = t;
} else {
t->buffer->transaction = NULL;
kfree(t);
binder_stats_deleted(BINDER_STAT_TRANSACTION);
}
break;
}

done:
*consumed = ptr - buffer;
if (proc->requested_threads + proc->ready_threads == 0 &&
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 */) {
[// if (proc->requested_threads + proc->ready_threads == 0 &&
这个if语句判断是否需要请求当前线程所属的进程增加一个新的Binder线程来处理进程间通信请求。
]// if (proc->requested_threads + proc->ready_threads == 0 &&
proc->requested_threads++;
binder_debug(BINDER_DEBUG_THREADS,
"binder: %d:%d BR_SPAWN_LOOPER\n",
proc->pid, thread->pid);
if (put_user(BR_SPAWN_LOOPER, (uint32_t __user *)buffer))
return -EFAULT;
}

return 0;
}
]// ret = binder_thread_read(proc, thread, (void __user *)bwr.read_buffer, bwr.read_size, &bwr.read_consumed, filp->f_flags & O_NONBLOCK)

if (!list_empty(&proc->todo))
wake_up_interruptible(&proc->wait);
if (ret < 0) {
if (copy_to_user(ubuf, &bwr, sizeof(bwr)))
ret = -EFAULT;
goto err;
}
}
binder_debug(BINDER_DEBUG_READ_WRITE,
"binder: %d:%d wrote %ld of %ld, read return %ld of %ld\n",
proc->pid, thread->pid, bwr.write_consumed, bwr.write_size,
bwr.read_consumed, bwr.read_size);
if (copy_to_user(ubuf, &bwr, sizeof(bwr))) {
ret = -EFAULT;
goto err;
}
break;
}