From: Chris Telting [telting-ml@mindspring.com]
Sent: Thursday, October 26, 2000 1:11 PM
To: NT Developers Interest List
Subject: [ntdev] Re: Can any one tell me what's wrong with this filter
code?

> However technically you can't do:
> 
> > > >    KeSetEvent(event, 0, FALSE) ;
> > > > 
> > > >    if (NT_SUCCESS(Irp->IoStatus.Status))
> > > >       DbgPrint("Transfer Success\n") ;
> > > >       else DbgPrint("Transfer Error\n") ;
> 
> in your completion handler as once you call KeSetEvent then the IRP can be
> completed in your dispatch routine before you get to your "if" statement
> that references the IRP.

Good point.

But that's only debug code I put in after the fact to try to
figure stuff out.  I WOULD know if it triggered a page fault
which is the worst it could do.

> Actually it just hit me what the problem is here. I was looking at the fact
> that you comment out the IrpPending test, and I was thinking that this could
> be a source of the problem. Then I re-examined the dispatch side and:

I left that commented code in just to show that I was aware of it
and had tried it.

> 
> > > >          status = IoCallDriver(devExt->NextDevice, Irp) ;
> > > >          KeWaitForSingleObject(&event, Executive, 
> > KernelMode, FALSE, NULL) ;
> > > >          DbgPrint("Continue and Complete\n") ;
> > > > 
> > > >          IoCompleteRequest(Irp, IO_NO_INCREMENT) ;
> > > > 
> > > >          return status ;
> 
> The problem is that you are returning the value produced by the call to
> IoCallDriver. Bad news if IoCallDriver returned STATUS_PENDING! You should
> instead be setting status to Irp->IoStatus.Status, ASSERTing that status
> does not equal STATUS_PENDING and returning that value.

Ok I'll try that though I think I use to return Irp->IoStatus.Status
in a previous incarnation but it wouldn't hurt to try it again.  Here
goes... (Trying not to get my hopes up so it doesn't jinx it)

      case URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER:
         {
         KIRQL Irql ;
         KEVENT event ;

         DbgPrint("URB Function: URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER\n") ;

         Irql = KeGetCurrentIrql() ;
         if (Irql == PASSIVE_LEVEL)
            DbgPrint("IRQL: PASSIVE_LEVEL (%u)\n", Irql) ;
            else if (Irql == APC_LEVEL)
            DbgPrint("IRQL: APC_LEVEL (%u)\n", Irql) ;
            else if (Irql == DISPATCH_LEVEL)
            DbgPrint("IRQL: DISPATCH_LEVEL (%u)\n", Irql) ;
            else DbgPrint("IRQL: %u\n", Irql) ;

         KeInitializeEvent(&event, NotificationEvent, FALSE) ;
         IoCopyCurrentIrpStackLocationToNext(Irp) ;
         IoSetCompletionRoutine(Irp, (PIO_COMPLETION_ROUTINE)InterruptTransferComplete, &event, TRUE, TRUE, TRUE) ;
         status = IoCallDriver(devExt->NextDevice, Irp) ;
         KeWaitForSingleObject(&event, Executive, KernelMode, FALSE, NULL) ;
         DbgPrint("Continue and Complete\n") ;
         status = Irp->IoStatus.Status ;
         ASSERT(status != STATUS_PENDING) ;

         IoCompleteRequest(Irp, IO_NO_INCREMENT) ;

         return status ;
         } ;

NTSTATUS InterruptTransferComplete(PDEVICE_OBJECT DeviceObject, PIRP Irp, PVOID Data)
   {
2   PKEVENT  event ;

   DbgPrint("InterruptTrandferComplete\n") ;

// Shouldn't matter because we are signaling an event to continue in
// the dispatch function.
//
//   if (Irp->PendingReturned)
//      {
//      DbgPrint("IoMarkIrpPending\n") ;
//      IoMarkIrpPending(Irp) ;
//      } ;

   if (NT_SUCCESS(Irp->IoStatus.Status))
      DbgPrint("Transfer Success\n") ;
      else DbgPrint("Transfer Error\n") ;

   event = (PKEVENT)Data ;

   KeSetEvent(event, 0, FALSE) ;

   return STATUS_MORE_PROCESSING_REQUIRED ;
   } ;


(Says the lord prayer and crosses himself)

...

(softice)
Break due to KeBugCheckEx (Unhandled kernel mode exception)
Error=7F(UNEXPECTED_KERNEL_MODE_TRAP) P1=8 P2=0 P3=0 P4=0

Same on blue screen on go

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