说明

thread封装了pthread, 完成的功能是, 使用fixed_queue作为workquque, 将需要被执行的thread function放入其中(enqueue), 使用thread_post来enqueue,enqueue完成后semophore发送信号给dequeue, 然后使用reactor中的epoll_wait监控到dequeue semaphore变更, 就读出queue中的数据, 而queue中的item是thread function与args, 于是运行这个function, 完成任务执行功能. 

结构体

struct thread_t { bool is_joined; pthread_t pthread; pid_t tid; char name[THREAD_NAME_MAX + 1]; reactor_t *reactor; // 对dequeue semophore fd进行监听 fixed_queue_t *work_queue; //存放work_item }; struct start_arg { thread_t *thread; semaphore_t *start_sem; int error; }; typedef struct { //用于thread_post传递需要的执行的function以及function需要的args thread_fn func; void *context; } work_item_t;

函数分析

创建thread以及reactor

thread_t *thread_new_sized(const char *name, size_t work_queue_capacity) { assert(name != NULL); assert(work_queue_capacity != 0); thread_t *ret = osi_calloc(sizeof(thread_t)); if (!ret) goto error; ret->reactor = reactor_new(); if (!ret->reactor) goto error; ret->work_queue = fixed_queue_new(work_queue_capacity); if (!ret->work_queue) goto error; // Start is on the stack, but we use a semaphore, so it's safe struct start_arg start; start.start_sem = semaphore_new(0); if (!start.start_sem) goto error; strncpy(ret->name, name, THREAD_NAME_MAX); start.thread = ret; start.error = 0; pthread_create(&ret->pthread, NULL, run_thread, &start); semaphore_wait(start.start_sem); // A1:等待run_thread执行后,且使用prctl更改名字成功才返回 等待thread_post中进行唤醒才会退出,在那之前包装pthread_create创建出来的thread function可以一直执行, 这里返回即为主线程的退出 semaphore_free(start.start_sem); if (start.error) //error值在run_pthread中设置的,见下面的B1 goto error; return ret; error:; if (ret) { fixed_queue_free(ret->work_queue, osi_free); reactor_free(ret->reactor); } osi_free(ret); return NULL; }

thread_post

完成thread的main_loop函数设置

bool thread_post(thread_t *thread, thread_fn func, void *context) { assert(thread != NULL); assert(func != NULL); // TODO(sharvil): if the current thread == |thread| and we've run out // of queue space, we should abort this operation, otherwise we'll // deadlock. // Queue item is freed either when the queue itself is destroyed // or when the item is removed from the queue for dispatch. work_item_t *item = (work_item_t *)osi_malloc(sizeof(work_item_t)); if (!item) { LOG_ERROR("%s unable to allocate memory: %s", __func__, strerror(errno)); return false; } item->func = func; //设置回调函数 item->context = context; fixed_queue_enqueue(thread->work_queue, item);//A4: enqueue后dequeue的semophore会从epoll_wait中回来, 然后就会去dequeue.对应B4 return true; }

run_thread阻塞等待poll_wait

static void *run_thread(void *start_arg) { assert(start_arg != NULL); struct start_arg *start = start_arg; thread_t *thread = start->thread; assert(thread != NULL); if (prctl(PR_SET_NAME, (unsigned long)thread->name) == -1) { LOG_ERROR("%s unable to set thread name: %s", __func__, strerror(errno)); start->error = errno; // B1:设置thread name失败 semaphore_post(start->start_sem);//B2:设置好了error变量可以让new_thread返回退出了. return NULL; } thread->tid = gettid(); semaphore_post(start->start_sem); //B3: 同B2 int fd = fixed_queue_get_dequeue_fd(thread->work_queue); void *context = thread->work_queue; reactor_object_t *work_queue_object = reactor_register(thread->reactor, fd, context, work_queue_read_cb, NULL);//B4:注意里面fd是dequeue的fd,因此在enqueue后actor会执行workqueue_read_cb读取queue的数据进行处理 reactor_start(thread->reactor); //B5: poll_wait,等待enqueue来唤醒自己,在没有enqueue之前都是休眠,有了enqueue就是有需要执行的任务(item->func)需要执行了. reactor_unregister(work_queue_object); // Make sure we dispatch all queued work items before exiting the thread. // This allows a caller to safely tear down by enqueuing a teardown // work item and then joining the thread. size_t count = 0; work_item_t *item = fixed_queue_try_dequeue(thread->work_queue); while (item && count <= fixed_queue_capacity(thread->work_queue)) { item->func(item->context); //取出callback函数进行执行 osi_free(item); item = fixed_queue_try_dequeue(thread->work_queue);//逐个取出 ++count; } if (count > fixed_queue_capacity(thread->work_queue)) LOG_DEBUG("%s growing event queue on shutdown.", __func__); return NULL; }

使用

下面以hci_layer.c中的thread为例说明一下使用.

1. 使用thread_new创建thread

这里仅仅传入thread name:

thread = thread_new("hci_thread"); if (!thread) { LOG_ERROR("%s unable to create thread.", __func__); goto error; } 这里面静默创建了reactor与fixed_queue.  

2. 使用thread_post注册thread需要处理的function,即enqueue item function,然后唤醒run_thread dequeue来执行

下面这个就是event_finish_startup为需要执行的函数

thread_post(thread, event_finish_startup, NULL);

这个注册的函数定义如下, 这里面可以看到调用到了HAL层的open, 即libbt-vendor.so中的open, 在switch中的"case BT_VND_OP_USERIAL_OPEN".

static void event_finish_startup(UNUSED_ATTR void *context) { LOG_INFO("%s", __func__); hal->open(); vendor->send_async_command(VENDOR_CONFIGURE_FIRMWARE, NULL); }

对于case BT_VND_OP_USERIAL_OPEN, 可以查看文件hardware/broadcom/libbt/src/bt_vendor_brcm.c中的代码, 这里面调用到了硬件操作, 例如:

case BT_VND_OP_USERIAL_OPEN: { int (*fd_array)[] = (int (*)[]) param; int fd, idx; ALOGW("--------- BT_VND_OP_USERIAL_OPEN Done ------------"); fd = userial_vendor_open((tUSERIAL_CFG *) &userial_init_cfg); //Open硬件操作 if (fd != -1) { for (idx=0; idx < CH_MAX; idx++) (*fd_array)[idx] = fd; retval = 1; } /* retval contains numbers of open fd of HCI channels */ } break; dequeue取出后执行这个函数, 然后返回.