usb摄像头驱动不能卸载

按照usbintel编写了摄像头驱动，正常使用是可以卸载的，但是在读取图像的时候，突然拔掉摄像头，上层应用程序不能退出线程，怀疑会有irp或srb在pending状态。在usb拔掉后，捕获到SRB_SURPRISE_REMOVAL，ddk文档说
usbcamd对SRB_SURPRISE_REMOVAL 的处理如下
USBCAMD: Cancel pending data SRBs and return the SRBs with STATUS_CANCELLED.
USBCAMD: Call CamStopCaptureEx/CamFreeBandwidthEx on all opened streams
USBCAMD: Return STATUS_CANCELLED on any read/write SRBs that come down after SRB_SURPRISE_REMOVAL.
但不知道为什么没有cancel成功呢？
下面是我的log

'INTELCAM:
'rawFrameBuffer:  84a80000
'INTELCAM:
'RawFrameLength:  8000
'INTELCAM:
'JpegStart:  84a80000
'INTELCAM:
'JpegLength:  2969
'INTELCAM:
'INTELCAM_ReceiveDataPacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'SRB_SURPRISE_REMOVAL!!
'INTELCAM:
'INTELCAM_StopVideoCaptureEx
'INTELCAM:
'INTELCAM_StopVideoCapture
'INTELCAM:
'INTELCAM_FreeBandwidthEx
'INTELCAM:
'INTELCAM_FreeBandwidth

这时候线程就死在这里了，强制退出程序后，有如下log

'INTELCAM:
'INTELCAM_ProcessRawVideoFrameEx
'INTELCAM:
'INTELCAM_ProcessRawVideoFrame
'INTELCAM:
'FrameLength:0  RawFrameLength:0
'INTELCAM:
'================================!
'INTELCAM:
'INTELCAM_ProcessRawVideoFrameEx
'INTELCAM:
'INTELCAM_ProcessRawVideoFrame
'INTELCAM:
'FrameLength:0  RawFrameLength:0
'INTELCAM:
'================================!
'INTELCAM:
'INTELCAM_ProcessRawVideoFrameEx
'INTELCAM:
'INTELCAM_ProcessRawVideoFrame
'INTELCAM:
'FrameLength:0  RawFrameLength:0
'INTELCAM:
'================================!
'INTELCAM:
'INTELCAM_ProcessRawVideoFrameEx
'INTELCAM:
'INTELCAM_ProcessRawVideoFrame
'INTELCAM:
'FrameLength:0  RawFrameLength:0
'INTELCAM:
'================================!
'INTELCAM:
'INTELCAM_ProcessRawVideoFrameEx
'INTELCAM:
'INTELCAM_ProcessRawVideoFrame
'INTELCAM:
'FrameLength:0  RawFrameLength:0
'INTELCAM:
'================================!
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
INTELCAM_UnInitialize
'INTELCAM:
UnInitialize
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'Driver Entry
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'INTELCAM_HwInitialize
'INTELCAM:
'INTELCAM_ConfigureEx
'INTELCAM:
'INTELCAM_Configure
'INTELCAM:
''Configure 0x0
'INTELCAM:
'PipeConfigListSize:2
'INTELCAM:
INTELCAM_Initialize
'INTELCAM:
InitializeHardware 0x0
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
GetStreamFormatsArray
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
INTELCAM_CompleteInitialization
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket
'INTELCAM:
'AdapterReceivePacket

线程被退出，驱动被卸载

多谢gutian98兄指点
我也知道是没有cancel掉，我是这样做的，但还不成
在INTELCAM_CompleteInitialization中会得到一个USBCAMD_INTERFACE，并把它保存在DeviceContext->pDeviceObject中。
截获SRB_SURPRISE_REMOVAL(也就是拔掉usb设备的消息)，并进行deviceContext->UsbcamdInterface.USBCAMD_CancelBulkReadWrite(deviceContext,0);
也就是对我的第0个管道进行cancel读取。不知道这样的思路对不对。
现在是有十次插拔，能有一两次能正确卸载，大多数还是不能卸载。
我想大概是每次读取的srb，usbcamd会对他们进行排队，不知道有什么方法可以将这些排队的srb,逐个cancel掉。