WhyCan Forum(哇酷开发者社区)

用的是V3s 4.13的版本，已经在menuconfig中设置了Kernel debugging，Kernel low-level debugging functions
在usb_disconnect这个函数中加了几句话，如下

void usb_disconnect(struct usb_device **pdev)
{
    struct usb_port *port_dev = NULL;
    struct usb_device *udev = *pdev;
    struct usb_hub *hub = NULL;
    int port1 = 1;
    printk(KERN_NOTICE, "usb_disconnect begin\n");

    /* mark the device as inactive, so any further urb submissions for
     * this device (and any of its children) will fail immediately.
     * this quiesces everything except pending urbs.
     */
    usb_set_device_state(udev, USB_STATE_NOTATTACHED);
    dev_info(&udev->dev, "AAUSB disconnect, device number %d\n",
            udev->devnum);
    _dev_info(&udev->dev, "BBBBUSB disconnect, device number %d\n",
            udev->devnum);
    printk(KERN_INFO, "---KERN_INFO usb_disconnect begin\n");
    printk(KERN_ALERT, "--- KERN_ALERTalert usb_disconnect begin\n");
    printk(KERN_WARNING, "---KERN_WARNING usb_disconnect begin\n");
    printk(KERN_NOTICE, "---KERN_WARNING usb_disconnect begin\n");
    printk(KERN_DEBUG, "---KERN_DEBUG usb_disconnect begin\n");
.....
}

输出结果为：
[   35.141543] usb 2-1: AAUSB disconnect, device number 3
[   35.146689] usb 2-1: BBBBUSB disconnect, device number 3

就是说dev_info，_dev_info两个函数可以输出，而printk函数没有输出，这是怎么回事啊？