Experimental Physics and
Industrial Control System

Jeff Hill <[email protected]> · Wed, 11 Mar 1998 09:37:35 -0700

On Tuesday, March 10, 1998 8:46 AM, Andrew Johnson [SMTP:[email protected]] wrote:
> Benjamin Franksen wrote:
> 
> > another proposal (suggested by Goetz Pfeiffer): Currently there is a
> > 'Symb' device support for ai, ao, longin, longout, stringin and
> > stringout records.
> ...
> > (1) To protect the data transport, simply add some
> > 
> >         intLock()
> >         ...
> >         intUnlock()
> 
> This is unnecessary as long as the value is read in a single cycle - for
> longs certainly, and possibly for doubles too (I'd need to check the
> compiler output to be sure of this one).  It may be worth doing this for
> strings and waveforms though (added by me, see below).
> 

I agree that this is normally only required for multi-element data such
as waveforms and strings.

It is almost always preferable to use a semTake()/semGive() of a vxWorks 
mutual exclusion semaphore instead of the intLock()/intUnlock() in task
level code. I prefer not to cause time critical ISRs to wait while we are 
copying an array in task level code. Frequently, it is also preferable to 
specify the task delete safe and priority inheritance options when creating 
a mutex semaphore in a code that will be used at many different sites.

Jeff

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System