: wakerfd_(::eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC)), loop_(loop),

wakerchannel_(std::make_unique<Channel>(loop, wakerfd_)) {

if (wakerfd_ < 0) {

KBACK_LOG_SYSERR("Failed in eventfd");

abort();

}

wakerchannel_->setReadCallback([this](Timestamp) { handleRead(); });

wakerchannel_->enableReading();

loop_->assertInLoopThread();

// 和wakeup函数对应，wakeup函数实际上是写事件，handleRead为对应的读事件

uint64_t one = 1;

ssize_t n = ::read(wakerfd_, &one, sizeof one);

// 判断读取的字节是不是 one对应的字节数

if (n != sizeof one) {

KBACK_LOG_ERROR("AsyncWaker::handleRead() reads %zd bytes instead of 8",

n);

}

uint64_t one = 1;

ssize_t n = ::write(wakerfd_, &one, sizeof one);

// 判断写入的字节是不是 one对应的字节数

if (n != sizeof one && errno != EAGAIN) {

KBACK_LOG_ERROR("AsyncWaker::wakeup() writes %zd bytes instead of 8", n);

}