Changing real time priority of interrupt handler thread

Changing real time priority of interrupt handler thread

[Raphael Hertzog]

[ Please cc me on answer, I'm not subscribed to the list, I tried to ask
this question on the #linux-rt channel but got no answers so I try on the
list ]

Hello,

with 2.6.33.2-rt13 the IRQ handler thread for serial devices is
no longer persistent after its creation. Up to now I had a startup
script opening the serial device in order to create the IRQ handler
thread that would run chrt on $(pidof IRQ-4) and the setting would be
persistent until next reboot.

This is no longer possible, I would have to run chrt every time that I
open the serial port and I would like to avoid modifying all my
applications to do this.

Is there any other alternative like making the thread persistent with some
options (/sys or /proc tuning)?

Or is there a kernel config option for this ?

In case it was not clear, I want to run the IRQ handler of the serial
ports at a higher priority than the other ones (like network, disk,
etc.) to avoid buffer overruns.

Cheers,
-- 
Raphaël Hertzog -+- http://www.ouaza.com

Freexian : des développeurs Debian au service des entreprises
http://www.freexian.com
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Re: Changing real time priority of interrupt handler thread

[Nivedita Singhvi]

Raphael Hertzog wrote:

> In case it was not clear, I want to run the IRQ handler of the serial
> ports at a higher priority than the other ones (like network, disk,
> etc.) to avoid buffer overruns.

Have you tried using the rtctl utility and the /etc/rtgroups file?


thanks,
Nivedita

Re: Changing real time priority of interrupt handler thread

[Steven Rostedt]

On Wed, 2010-05-05 at 11:37 -0700, Nivedita Singhvi wrote:
> Raphael Hertzog wrote:
> 
> > In case it was not clear, I want to run the IRQ handler of the serial
> > ports at a higher priority than the other ones (like network, disk,
> > etc.) to avoid buffer overruns.
> 
> Have you tried using the rtctl utility and the /etc/rtgroups file?

Also try out tuna. If you have fedora:

 yum install tuna

-- Steve

Re: Changing real time priority of interrupt handler thread

[Darcy L. Watkins]

On Thu, 2010-05-06 at 10:54 -0700, Steven Rostedt wrote:
> On Wed, 2010-05-05 at 11:37 -0700, Nivedita Singhvi wrote:
> > Raphael Hertzog wrote:
> >
> > > In case it was not clear, I want to run the IRQ handler of the
> serial
> > > ports at a higher priority than the other ones (like network,
> disk,
> > > etc.) to avoid buffer overruns.
> >
> > Have you tried using the rtctl utility and the /etc/rtgroups file?

Where are the source tarball projects for these located so I can try
porting/using them [at least some of it] on my embedded linux?  ... or
is this a proprietary Redhat utility only in RPM binaries?  Google
search seems to mainly land me at IBM and Redhat user docs and FAQs.

Perhaps my issue earlier with serial buffer overruns is just a tune up
issue.

I want to tune up RT on PowerPC 405 and ARM11 MX.31 based embedded
systems where the rootfs is built (cross compiled) using
buildroot/uclibc, etc and not x86 binaries from a full feature distro
such as Fedora, Debian, etc.


Darcy

> 
> Also try out tuna. If you have fedora:
> 
>  yum install tuna
> 
> -- Steve

Re: Changing real time priority of interrupt handler thread

[Nivedita Singhvi]

Darcy L. Watkins wrote:

>>> Have you tried using the rtctl utility and the /etc/rtgroups file?
> 
> Where are the source tarball projects for these located so I can try
> porting/using them [at least some of it] on my embedded linux?  ... or
> is this a proprietary Redhat utility only in RPM binaries?  Google
> search seems to mainly land me at IBM and Redhat user docs and FAQs.

rtctl is GPL, not proprietary. A quick google search brought
up the following:

http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/

http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/rtctl-1.7-1.el5rt.src.rpm

> Perhaps my issue earlier with serial buffer overruns is just a tune up
> issue.
> 
> I want to tune up RT on PowerPC 405 and ARM11 MX.31 based embedded
> systems where the rootfs is built (cross compiled) using
> buildroot/uclibc, etc and not x86 binaries from a full feature distro
> such as Fedora, Debian, etc.

Setting thread priorities for your environment will certainly
be a good thing in general.

thanks,
Nivedita

Re: Changing real time priority of interrupt handler thread

[Darcy L. Watkins]

On Tue, 2010-05-18 at 08:04 -0700, Nivedita Singhvi wrote:
> Darcy L. Watkins wrote:
> 
> >>> Have you tried using the rtctl utility and the /etc/rtgroups file?
> >
> > Where are the source tarball projects for these located so I can try
> > porting/using them [at least some of it] on my embedded linux?  ...
> or
> > is this a proprietary Redhat utility only in RPM binaries?  Google
> > search seems to mainly land me at IBM and Redhat user docs and FAQs.
> 
> rtctl is GPL, not proprietary. A quick google search brought
> up the following:

Excellent!  and thanks!  I see SRPMs for rt-setup, tuna, etc there as
well.  Is this FTP site the usual place to pick up SRPMs for these
utilities as they are updated / released?


Darcy

> 
> http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/
> 
> http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/rtctl-1.7-1.el5rt.src.rpm
> 
> > Perhaps my issue earlier with serial buffer overruns is just a tune
> up
> > issue.
> >
> > I want to tune up RT on PowerPC 405 and ARM11 MX.31 based embedded
> > systems where the rootfs is built (cross compiled) using
> > buildroot/uclibc, etc and not x86 binaries from a full feature
> distro
> > such as Fedora, Debian, etc.
> 
> Setting thread priorities for your environment will certainly
> be a good thing in general.
> 
> thanks,
> Nivedita

Re: Changing real time priority of interrupt handler thread

[Nivedita Singhvi]

Darcy L. Watkins wrote:

>>> is this a proprietary Redhat utility only in RPM binaries?  Google
>>> search seems to mainly land me at IBM and Redhat user docs and FAQs.
>> rtctl is GPL, not proprietary. A quick google search brought
>> up the following:
> 
> Excellent!  and thanks!  I see SRPMs for rt-setup, tuna, etc there as
> well.  Is this FTP site the usual place to pick up SRPMs for these
> utilities as they are updated / released?

I am definitely not authoritative on that - it was something
I happened to look up. You should definitely get the correct
info from RH folks (as it's theirs).

> Darcy
> 
>> http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/
>>
>> http://ftp.riken.go.jp/pub/Linux/cern/mrg/slc5X/SRPMS/rtctl-1.7-1.el5rt.src.rpm


thanks,
Nivedita

Re: Changing real time priority of interrupt handler thread

[Raphael Hertzog]

Hi,

Le mercredi 05 mai 2010, Nivedita Singhvi a écrit :
> Raphael Hertzog wrote:
> 
> >In case it was not clear, I want to run the IRQ handler of the serial
> >ports at a higher priority than the other ones (like network, disk,
> >etc.) to avoid buffer overruns.
> 
> Have you tried using the rtctl utility and the /etc/rtgroups file?

Nope, not yet. I was not aware of it.

Le jeudi 06 mai 2010, Steven Rostedt a écrit :
> Also try out tuna. If you have fedora:
> 
>  yum install tuna

I have Debian and none of the two tools quoted above seem to be packaged.
But thanks for your answers, I will check them out.

BTW I can't find a "rtctl" project, are the SRPM the official upstream
sources? For tuna there's a least a git repo.

Cheers,
-- 
Raphaël Hertzog -+- http://www.ouaza.com

Freexian : des développeurs Debian au service des entreprises
http://www.freexian.com
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Re: Changing real time priority of interrupt handler thread

[Steven Rostedt]

On Tue, 2010-05-25 at 15:02 +0200, Raphael Hertzog wrote:
> Hi,
> 
> Le mercredi 05 mai 2010, Nivedita Singhvi a écrit :
> > Raphael Hertzog wrote:
> > 
> > >In case it was not clear, I want to run the IRQ handler of the serial
> > >ports at a higher priority than the other ones (like network, disk,
> > >etc.) to avoid buffer overruns.
> > 
> > Have you tried using the rtctl utility and the /etc/rtgroups file?
> 
> Nope, not yet. I was not aware of it.
> 
> Le jeudi 06 mai 2010, Steven Rostedt a écrit :
> > Also try out tuna. If you have fedora:
> > 
> >  yum install tuna
> 
> I have Debian and none of the two tools quoted above seem to be packaged.
> But thanks for your answers, I will check them out.
> 

I have installed and used tuna on a Debian machine. It takes a bit to
get all the dependencies straight, but it is possible.

> BTW I can't find a "rtctl" project, are the SRPM the official upstream
> sources? For tuna there's a least a git repo.

I added Clark Williams to the Cc. He should be able to answer that
question.

-- Steve


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Re: Changing real time priority of interrupt handler thread

[Clark Williams]

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On Tue, 25 May 2010 09:25:41 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 2010-05-25 at 15:02 +0200, Raphael Hertzog wrote:
> > Hi,
> > 
> > Le mercredi 05 mai 2010, Nivedita Singhvi a écrit :
> > > Raphael Hertzog wrote:
> > > 
> > > >In case it was not clear, I want to run the IRQ handler of the serial
> > > >ports at a higher priority than the other ones (like network, disk,
> > > >etc.) to avoid buffer overruns.
> > > 
> > > Have you tried using the rtctl utility and the /etc/rtgroups file?
> > 
> > Nope, not yet. I was not aware of it.
> > 
> > Le jeudi 06 mai 2010, Steven Rostedt a écrit :
> > > Also try out tuna. If you have fedora:
> > > 
> > >  yum install tuna
> > 
> > I have Debian and none of the two tools quoted above seem to be packaged.
> > But thanks for your answers, I will check them out.
> > 
> 
> I have installed and used tuna on a Debian machine. It takes a bit to
> get all the dependencies straight, but it is possible.
> 
> > BTW I can't find a "rtctl" project, are the SRPM the official upstream
> > sources? For tuna there's a least a git repo.
> 
> I added Clark Williams to the Cc. He should be able to answer that
> question.
>

Hey Niv and Raphael,

Yeah  the official upstream for rtctl is currently the SRPM. Never
really anticipated that anyone would want it :)

Clark

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