Calcout using CA output link sometimes gets INVALID severity

["J. Lewis Muir" <jlmuir@imca-cat.org>]

I've got a problem with a calcout record where, if I do a dbpf
after iocInit on an ao record that has a forward link to the
calcout record which in turn reads the ao record VAL field and
writes a calculated value to an ai record using a Channel Access
output link, sometimes the calcout record's SEVR field will be
INVALID, and it does not write the calculated value to the ai
record.  This doesn't happen every time, but I can usually get
it to happen within 5 tries.  If I change the output link type
from CA to PP, the problem goes away.  Does anyone know what's
wrong?

To reproduce this, load the attached calcout-test.db into a
soft IOC like this:

  dbLoadRecords("calcout-test.db", "P=ioc23:")

And immediately after iocInit do a dbpf like this:

  dbpf("ioc23:Preset", "300.0")

Check the SEVR field from a Terminal like this:

  $ caget ioc23:PresetHistoryAdd.SEVR

Check the calculated value from a Terminal like this:

  $ caget -a ioc23:PresetHistory

Repeatedly stop and start the IOC until you succeed in
reproducing the problem.

Environment:
* Processor: 2.3 GHz Intel Core i7
* Memory: 8 GB
* OS: Mac OS X 10.8.2
* EPICS Base 3.14.12.2 (+ Known Problems patches)
  Architecture: darwin-x86
  OS Class: x86_64

Thanks,

Lewis

#
# If load this database and on the IOC console do a dbpf to $(P)Preset
# immediately after iocInit, sometimes $(P)PresetHistoryAdd.SEVR will be
# INVALID and $(P)PresetHistory will not get set to the value of $(P)Preset.
#
# Parameters:
#   $(P)    PV name prefix (e.g. "ioc23:")
#

record(ao, "$(P)Preset") {
  field(FLNK, "$(P)PresetHistoryAdd")
}

record(calcout, "$(P)PresetHistoryAdd") {
  field(INPA, "$(P)Preset.VAL NPPNMS")
  field(CALC, "A")
  field(OUT, "$(P)PresetHistory.VAL CA")
}

record(ai, "$(P)PresetHistory") {
}