Windows System Software -- Consulting, Training, Development -- Unique Expertise, Guaranteed Results


Before Posting...

Please check out the Community Guidelines in the Announcements and Administration Category.

More Info on Driver Writing and Debugging

The free OSR Learning Library has more than 50 articles on a wide variety of topics about writing and debugging device drivers and Minifilters. From introductory level to advanced. All the articles have been recently reviewed and updated, and are written using the clear and definitive style you've come to expect from OSR over the years.

Check out The OSR Learning Library at:

Completion Routine & Worker Thread Issue

0mWindyBug0mWindyBug Member Posts: 29
edited February 12 in NTDEV

Hey , I'm working on a filter driver that does some processing in a completion routine and in some common conditions needs to append a new item to a linked list protected with a Mutex
due to IRQL constraints I cant run the append part from the completion routine so I tried to queue a work item , something like this :
`NTSTATUS FilterReadCompletion(PDEVICE_OBJECT DeviceObject, PIRP Irp, PVOID Context)

auto status = Irp->IoStatus.Status;
if (Irp->PendingReturned)
if (Irp->IoStatus.Status == STATUS_SUCCESS)
    PKEYBOARD_INPUT_DATA InputData = (PKEYBOARD_INPUT_DATA)Irp->AssociatedIrp.SystemBuffer;
    int NumberOfKeysRead = Irp->IoStatus.Information / sizeof(KEYBOARD_INPUT_DATA);
    PWORK_QUEUE_ITEM workItem = new(NonPagedPool, TAG)WORK_QUEUE_ITEM;
    PKEYBOARD_INPUT_DATA Data = (PKEYBOARD_INPUT_DATA)ExAllocatePoolWithTag(NonPagedPool, sizeof(KEYBOARD_INPUT_DATA) * NumberOfKeysRead, TAG);
    if (Data && workItem && Context)
        // we have to copy the system buffer as by the time the worker will process it the IRP is likely to already be completed 
        RtlCopyMemory(Data, InputData, sizeof(KEYBOARD_INPUT_DATA) * NumberOfKeysRead);

        Context->Count = NumberOfKeysRead;
        Context->Data = Data;
        if (workItem)
            ExInitializeWorkItem(workItem, (PWORKER_THREAD_ROUTINE)FilterWorker, Context);
            ExQueueWorkItem(workItem, DelayedWorkQueue);

return status;


and the work item itself :
void FilterWorker(PDEVICE_OBJECT DeviceObject,PVOID Context) {
int NumberOfKeysRead = CompletionData->Count;

for (int i = 0; i < NumberOfKeysRead; i++)
    // record key only if it is a key press or a special key press / release
    if (InputData[i].Flags == KEY_MAKE || IsSpecialMakecode(InputData[i].MakeCode))
        Recording.Append(InputData[i].MakeCode, InputData[i].Flags);
ExFreePoolWithTag(InputData, TAG);
delete CompletionData;


Now , even if I only try to
DbgPrint("[*] Data 0x%p , Count %d\n",InputData,NumberOfKeysRead")
I get a bugcheck , any clear issue with what im doing ?
on another note, any lock that is possible to use at dispatch level ? im using a mutex but KeWaitForSingleObject is not allowed in some cases , it also triggered a bugcheck (SWITCH_FROM_DPC..)

Post edited by Scott_Noone_(OSR) on
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. Sign in or register to get started.

Upcoming OSR Seminars
OSR has suspended in-person seminars due to the Covid-19 outbreak. But, don't miss your training! Attend via the internet instead!
Kernel Debugging 13-17 May 2024 Live, Online
Developing Minifilters 1-5 Apr 2024 Live, Online
Internals & Software Drivers 11-15 Mar 2024 Live, Online
Writing WDF Drivers 20-24 May 2024 Live, Online