status_t BufferQueueProducer::queueBuffer(int slot,

        const QueueBufferInput &input, QueueBufferOutput *output) {

    ATRACE_CALL();

    ...

    BufferItem item;

    { // Autolock scope

    ...

        output->width = mCore->mDefaultWidth;

        output->height = mCore->mDefaultHeight;

        output->transformHint = mCore->mTransformHintInUse = mCore->mTransformHint;

        output->numPendingBuffers = static_cast<uint32_t>(mCore->mQueue.size());

        output->nextFrameNumber = mCore->mFrameCounter + 1;

        ATRACE_INT(mCore->mConsumerName.string(),

                static_cast<int32_t>(mCore->mQueue.size()));//知识点1

        ...

    } // Autolock scope

    // Wait without lock held

    if (connectedApi == NATIVE_WINDOW_API_EGL) {

        // Waiting here allows for two full buffers to be queued but not a

        // third. In the event that frames take varying time, this makes a

        // small trade-off in favor of latency rather than throughput.

        lastQueuedFence->waitForever("Throttling EGL Production");//知识点2

    }

    return NO_ERROR;

}