Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Thu, 7 Mar 2002 18:02:15 -0700

This is an EPICS bug alert.

Effected versions: 
	EPICS R3.13.5 only. 

Likely symptom: 
	A Channel Access client, such as medm, does not receive its
first 
	monitor subscription update when using very large numbers of
process variables. An "events lost" message will show up on the
IOC's console and in the log server.

Resolution:
	I have committed a patch to CVS. The APS will be making a new
EPICS
 	R3.13 release available soon.

Cause:
	This bug was discovered during regression testing of EPICS
R3.14. A 	patch made to EPICS R3.14 was also back patched into
EPICS R3.13.5. 
	This patch was flawed so that Channel Access monitor
subscription 
	updates may be lost if a client uninstalls many monitor
subscriptions and then immediately installs many new monitor 
	subscriptions. The CA server's event queue always retains space 
	for at least one update for each subscription that is installed.

	During subscription uninstall dummy entries could end up in the 
	event queue and these entries were using event queue space after
there associated monitor subscriptions were released. This could
cause a new subscription to be attached to an event queue when there
was not enough space for the first subscription update.

Jeff
__________________________________________________________
Jeff Hill                     Internet     [email protected]
LANL MS H820                  Voice        505 665 1831
Los Alamos NM 87545 USA       FAX          505 665 5107

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System