Re-entrancy in Filter Driver

NTFSD
1

Hi,
Are there any issues with using thread-id to identify re-entrance in
Filter Driver. The one was listed in IFS FAQ as if any driver does a stack
switch. Beside that, are there any issues which need to be taken care.

Thanks
Ashish

2

>Are there any issues with using thread-id to identify re-entrance in Filter

Driver

The problem with that is it will only identify re-entrancy by the same
thread. There are filters that will post a recursive operation to another
thread and then block in the original thread, which will fool your thread ID
check.

-scott

–
Scott Noone
Consulting Associate
OSR Open Systems Resources, Inc.
http://www.osronline.com

“Ashish Goyal” wrote in message
news:xxxxx@ntfsd…
Hi,
Are there any issues with using thread-id to identify re-entrance in
Filter Driver. The one was listed in IFS FAQ as if any driver does a stack
switch. Beside that, are there any issues which need to be taken care.

Thanks
Ashish

3

Thanks Scott…If we are not bothered about request initiated by filter
drivers and only applications (say file open by word) then is it safe to use
this technique…

Thanks
Ashish

On Thu, Nov 5, 2009 at 9:07 PM, Scott Noone wrote:

> >Are there any issues with using thread-id to identify re-entrance in
> Filter
> >Driver
>
> The problem with that is it will only identify re-entrancy by the same
> thread. There are filters that will post a recursive operation to another
> thread and then block in the original thread, which will fool your thread
> ID
> check.
>
> -scott
>
> –
> Scott Noone
> Consulting Associate
> OSR Open Systems Resources, Inc.
> http://www.osronline.com
>
>
> “Ashish Goyal” wrote in message
> news:xxxxx@ntfsd…
> Hi,
> Are there any issues with using thread-id to identify re-entrance in
> Filter Driver. The one was listed in IFS FAQ as if any driver does a stack
> switch. Beside that, are there any issues which need to be taken care.
>
> Thanks
> Ashish
>
>
>
> —
> NTFSD is sponsored by OSR
>
> For our schedule of debugging and file system seminars
> (including our new fs mini-filter seminar) visit:
> http://www.osr.com/seminars
>
> To unsubscribe, visit the List Server section of OSR Online at
> http://www.osronline.com/page.cfm?name=ListServer
>

4

Ashish Goyal wrote:

Thanks Scott…If we are not bothered about request initiated by filter
drivers and only applications (say file open by word) then is it safe to
use this technique…

What Scott is referring to does not require the request to be initiated
by another filter. It can be any request which some filter offloads to a
worker thread and it will break the thread id model.

Pete

Thanks
Ashish

On Thu, Nov 5, 2009 at 9:07 PM, Scott Noone > mailto:xxxxx> wrote:
>
> >Are there any issues with using thread-id to identify re-entrance
> in Filter
> >Driver
>
> The problem with that is it will only identify re-entrancy by the same
> thread. There are filters that will post a recursive operation to
> another
> thread and then block in the original thread, which will fool your
> thread ID
> check.
>
> -scott
>
> –
> Scott Noone
> Consulting Associate
> OSR Open Systems Resources, Inc.
> http://www.osronline.com http:</http:>
>
>
> “Ashish Goyal” > mailto:xxxxx> wrote in message
> news:xxxxx@ntfsd…
> Hi,
> Are there any issues with using thread-id to identify re-entrance in
> Filter Driver. The one was listed in IFS FAQ as if any driver does a
> stack
> switch. Beside that, are there any issues which need to be taken care.
>
> Thanks
> Ashish
>
>
>
> —
> NTFSD is sponsored by OSR
>
> For our schedule of debugging and file system seminars
> (including our new fs mini-filter seminar) visit:
> http://www.osr.com/seminars
>
> To unsubscribe, visit the List Server section of OSR Online at
> http://www.osronline.com/page.cfm?name=ListServer
>
>
> — NTFSD is sponsored by OSR For our schedule of debugging and file
> system seminars (including our new fs mini-filter seminar) visit:
> http://www.osr.com/seminars To unsubscribe, visit the List Server
> section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer

–
Kernel Drivers
Windows File System and Device Driver Consulting
www.KernelDrivers.com
866.263.9295</mailto:xxxxx></mailto:xxxxx>