为什么pIrp的值是NULL

pIrp是0的话，会导致我下面的程序出问题吗？

VOID TestWdmTimerDpc(
   IN PKDPC pDpc,
   IN PVOID pContext,
   IN PVOID SysArg1,
   IN PVOID SysArg2)
{
   DbgPrint(\"Starting TestWdmTimerDpc.\\n\");
   PDEVICE_OBJECT pDevObj = (PDEVICE_OBJECT)pContext;
   PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pDevObj->DeviceExtension;

   PIRP pIrp = pDevObj->CurrentIrp;
   RtlCopyMemory(pIrp->AssociatedIrp.SystemBuffer,\"1234567890\",10); // add
   pIrp->IoStatus.Information = 10L;           // 缓冲的长度         // add
   pIrp->IoStatus.Status = STATUS_SUCCESS;
}

当然

pIrp是0的话，会导致我下面的程序出问题吗？

VOID TestWdmTimerDpc(
   IN PKDPC pDpc,
   IN PVOID pContext,
   IN PVOID SysArg1,
   IN PVOID SysArg2)
{
   DbgPrint(\"Starting TestWdmTimerDpc.\\n\");
   PDEVICE_OBJECT pDevObj = (PDEVICE_OBJECT)pContext;
   PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pDevObj->DeviceExtension;

   PIRP pIrp = pDevObj->CurrentIrp;
   RtlCopyMemory(pIrp->AssociatedIrp.SystemBuffer,\"1234567890\",10); // add
   pIrp->IoStatus.Information = 10L;           // 缓冲的长度         // add
   pIrp->IoStatus.Status = STATUS_SUCCESS;
}