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From: RayU on 18 Apr 2008 10:39
Yes, I have tried every possible combination of the execution level and
synchronization scope. Why would there be any difference from XP? I worked
around this problem in the last project by altering the design for our DMA
based device. Now I am working on a new driver for XPx64 and wanted to see
if anyone had any ideas because this device will "require" IOCTL and
Read/Write based usage. Thus until I can resolve this issue I guess the WDM
will be required. I really wanted to develop this new driver with the KMDF
framework. I wanted to build the previous driver with the WDK 6001 RTM
Server 2008 product and see if this issue simply disapeared? but they need
this new drive in a month, and I do not believe I can wait until the Server
2008 WDK appears once again. First they said mid March, then Mid April and
still it is not avaiable.

"Doron Holan [MSFT]" wrote:

> did you set a sync scope or execution level?
>
> --
> Please do not send e-mail directly to this alias. this alias is for
> newsgroup purposes only.
> This posting is provided "AS IS" with no warranties, and confers no rights.
>
>
> "RayU" <rayu(a)discussions.microsoft.com> wrote in message
> news:164CC3CE-3FA2-408B-9468-A7C63B02709F(a)microsoft.com...
> > With XP the dispatch of DeviceIoControl from default device queue WDFQUEUE
> > functions correctly. With XPx64 when a user mode thread is at realtime
> > thread priority, and is issuing IOCTL's to the KMDF framework there is a
> > delay associated with the user mode thread recieving the frames from a
> > video
> > capture pci device operating at a meager ~16 m.s. rate. I do not
> > understand
> > why the design functions correctly under XP and not XPx64. Basically the
> > default deviceiocontrol callback inserts the request in a manual queue via
> > WdfRequestForwardToIoQueue and then makes and attemp to start a dma
> > operation
> > by dequeue from manual, spinlock some hardware registers, and then execute
> > the dma transaction via KMDF dma methodologies. The Request is completed
> > later when the dma is completed. However if I define a WDM preprocess
> > callback an raise the IRQ level the design works the same as it does under
> > XP. WHY??
> >
> > This is the magic which makes the XPx64 build of the exact same source
> > which
> > works fine under XP.
> >
> > NTSTATUS
> > SeWdmDeviceCntrlPreprocessCallback(
> > IN WDFDEVICE Device,
> > IN PIRP Irp
> > )
> > {
> > NTSTATUS status = STATUS_SUCCESS;
> >
> > IoSkipCurrentIrpStackLocation(Irp);
> >
> > KIRQL OldIrql = KeRaiseIrqlToDpcLevel();
> >
> > status = WdfDeviceWdmDispatchPreprocessedIrp(Device, Irp);
> >
> > KeLowerIrql( OldIrql );
> > return status;
> > }
> >
> > The problem occurs when the CPU load is at 100%. The thread issueing the
> > IOCTL's is elivated to realtime.
> >
> >
> >
>
>
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