Experimental Physics and
Industrial Control System

<[email protected]> · Thu, 23 Apr 2009 05:46:55 +0900

Hi Andrew,

Thank you VERY MUCH for your information. I got it.

I'm thinking of using the priority-based sheduling on a
dedicated embedded controller on the control network.
So, running EPICS as root should be OK.

(Acutually, we have already been running EPICS as root on
the controller...)

I surely look into epicsTreadPriorityTest to see how it
works.

Thank you again for your help.

Jun-ichi

----- Original Message -----
> Hi Jun-ichi,
> 
> On Wednesday 22 April 2009 07:47:51 [email protected] wrote:
> >
> > Thank you very much for the information.
> >
> > Just say "YES"...
> > Is that all what I have to do?
> 
> Well, almost.  Linux only allows processes to use the pthreads real-
time 
> priorities if the process is sufficiently privileged (because it's 
easy to 
> code a Denial of Service attack to bring down the OS if you have that 
> privilege).  There's probably a Capability (CAP_xx) that controls this,
 but I 
> don't know what it is.  The easiest way to provide that is to run the 
IOC as 
> root, which I don't recommend on a general-use system for security 
reasons 
> but should be Ok on a dedicated machine.
> 
> There is a test program called epicsThreadPriorityTest that you can 
run from 
> your base/src/libCom/test/O.<arch> directory which tells you whether 
the 
> threads are being scheduled strictly by priority or not, so you should 
be 
> able to use that to experiment.
> 
> HTH,
> 
> - Andrew
> 
> > ----- Original Message -----
> >
> > > [email protected] wrote:
> > > > Dear All;
> > > >
> > > > I've recently come to notice that the real-time performance of 
Linux
> > > > kernel is incredibly improving (against my expectations).
> > > >
> > > > http://www.osadl.org/Single-View.111+M5b96e97f67b.0.html
> > > >
> > > > I'd like to know if the implementation of OSD-library is 
implemented
> >
> > in
> >
> > > > such a manner that the kernel-level threads can reflect the 
priority
> > > > given by the user to the scheduling of epicsThreads?
> > > >
> > > > In other words, can I benefit from the improvement of Linux 
kernel
> > > > without making any changes in EPICS source codes?
> > >
> > > in file base/configure/CONFIG_SITE
> > >
> > > change
> > >
> > > USE_POSIX_THREAD_PRIORITY_SCHEDULING = NO
> > >
> > > to
> > >
> > > USE_POSIX_THREAD_PRIORITY_SCHEDULING = YES
> > >
> > > Also you must start the IOC as root.
> > >
> > > Marty
> 
> 
> 
> -- 
> The best FOSS code is written to be read by other humans -- Harold 
Welte
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System