NIFgen/NIScope on RedHat 5.x

[kcc1967]

Hi,

I used NIFgen/NIScope on OpenSuSE 10.3 for a while and it works OK.

Recently, I have a customer who use RedHat Enterprise 5.x and want to use

NIFgen/NIScope ... however, these boards is not supported by NI.

Change Linux distribution is not an option for my customer ... so my question is

if  it is worthy to try NIFgen/NIScope on RH5.x by myself.

Is it possible to make NIFgen/NIScope work on RH5.x by change kernel parameters

and rebuild the kernel ?  If this approach is OK, we can maintain the customized kernel

for our customers by ourselves.

Please give me some technical suggestion, Thanks a lot.

Regards

KC

[Chris_W.]

Hi KC,

Unfortunately there has not been testing done on Red Hat for those drivers. What versions of the two drivers are you using? I am assuming that it is NI-Scope 2.9 and NI-FGEN 2.4.1. The thing is that if you do end up getting those drivers working on a Red Hat distribution, you have to be aware that any scope or fgen board that is not supported in those versions of the drivers would not be recognized on that new OS. This would likely include a lot of the newer boards. It is really up to you whether this would be worth the time to get it up and running, if it's possible and it would be at your own risk unfortunately.

Here is a knowledgebase article that addresses the install of those drivers on RHEL 5. Make sure you read the message at the bottom of the article associated with the "x" that is in the table for RHEL 5 for NI-Scope and NI-Fgen. There are numerous issues with RHEL 5 and those drivers, which result in possible system crashes and such. I hope this helps.

Chris W

[kcc1967]

Hi Chris,

Thanks for reply.

However, your suggestion is more policy base instead of knowledge base suggestion to me.

And base on that, I believe everyone will simply say ... No, I will not use RH5x.

Well, that's not the answer I expected.  Is it possible you can tell me why RH 5x can't work with NIScope/NIFgen ?

It's hard to believe that the same driver can work on OpenSuSE 10.3 but fail to port to RH5x !!  Or require

a lot of effort to port to RH5x or other distribution.

I also believe it's 100% possible to move the Linux kernel/distribution support issue from NI to Linux community

or 3rd party without release the complete source code of NI's drivers to public if the interface between

kernel and NI's driver is open.  The NI-KAL is very close to this concept ... and probably just one more

step from NI will be enough.   Hopefully, I will see that happen.

Thanks

KC

[Shawn B.]

Hey KC,

The main thing that keeps NI-FGEN, and NI-SCOPE from working on RHEL 5 is that Red Hat builds their kernels with a 4K kernel stack instead of the default 8K that almost every other distribution uses.  When we say that a driver is officially supported on a Linux distribution it means that we have exercised the driver using our automated and manual test suites and found no major issues.  When testing on RHEL 5 we encountered kernel stack overflows that we felt would take too much effort to fix.

What does this mean for you or your customer?  Well, if you are familiar with the concept of a stack overflow, then you know that the stack depth depends on the code path being exercised.  So depending on the code paths and features used in the driver it is possible that you may never see a crash.  If you have an application that you expect will not change you can always test it to see if you can get the machine to crash.

You mentioned modifying RHEL's kernel to allow NI-FGEN, and NI-SCOPE to work.  This is possible especially if you have a little experience building kernels.  You can try rebuilding the stock RHEL 5 kernel by simply turning off the 4K kernel stack option.  I haven't tried this recently (on the newest kernels), but in the older kernels sometimes it was easy and sometimes it was difficult.  Red Hat applies many patches to their kernels and I have seen them apply patches that disable the ability to turn off 4K stacks, and/or apply patches that assume the kernel was built with 4K stacks.  So in some cases you may need to revert some of the patches applied to their kernel.

You could go grab a copy of Linus' kernel from kernel.org and build it yourself with the default 8K kernel stack of course.  If you do this I wouldn't use 2.6.29 yet since I know that NI-KAL 1.9 + NI-SCOPE/FGEN won't work.

You could also try one of the linuxant kernels for RHEL 5, since they have rebuilt the kernels to have a 16K stack.

Keep in mind with any of the solutions above NI has not run our test suites to verify everything works so you would need to perform the testing to ensure everything works to your satisfaction.

Shawn Bohrer

National Instruments

[kcc1967]

Hi Shawn,

Your reply is exactly what I'm looking for.   Thanks a lot.

If the 4K stack is the key issue, I think it's worthy to try NIScope/NIFgen

on RH5x, since we already use patched hard real-time kernel on RH5x for our customer.

Regards

KC