Experimental Physics and
Industrial Control System

Dear folks,  Emmanuel Mayssat inspired me to play with links, and I
found something interesting.  The calcout record in EPICS 3.14.7 (and
maybe other versions as well -- probably all versions since the record
acquired asynchronous device support) has a problem that results in an
infinite loop if two calcout records forward link to each other.
The scalcout record also has had this problem since synApps 5.1.

Here's the offending code in calcoutRecord.c.  (The corresponding
section of scalcoutRecord.c is almost identical):

static long process(...)
{
	...
	if(doOutput) {
		if (pcalc->odly > 0.0) {
			...
		} else {
			pcalc->pact = FALSE;
			execOutput(pcalc);
			if (pcalc->pact) return(0);
			<<< PACT should be set to TRUE here, but it isn't >>>
		}
	}
	...
	recGblFwdLink(pcalc);
	...

record(calcout,"a") {
	field(FLNK,"b")
}
record(calcout,"b") {
	field(FLNK,"a")
}

--
Tim Mooney ([email protected]) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab.

Replies:

Re: calcout/scalcout record problem in EPICS 3.14.7 Andrew Johnson

References:

labCA crashes with bad PV Dennis Nicklaus

Re: labCA crashes with bad PV Till Straumann

Re: labCA crashes with bad PV Dennis Nicklaus

FLNK loop Emmanuel Mayssat

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