Experimental Physics and
Industrial Control System

"Redman, Russell O." <[email protected]> · Thu, 27 Nov 2003 17:54:29 -0500

I am using sequencer v1.9.5 with EPICS R3.13.5 on a MVME2400.  

I have set up an event flag queue to monitor a process variable:
	double pos;
	assign  pos to "{axis}:px";
	evflag  posFlag;
	syncQ   pos posFlag; 
	monitor pos;  
This appears to work, but when I leave the IOC running overnight it always
crashes with messages of the form
	0x316f380 (EV_seqAux): proc_db_events_queued: 
			pos queue memory allocation failure

It will surprise no one that I have tracked this to a memory allocation bug.
In proc_db_events_queued() in seq_ca.c memory is allocated for each QENTRY:
		pEntry = (QENTRY *) calloc(sizeof(QENTRY), 1);
		...
		ellAdd(&pSP->pQueues[pDB->queueIndex], (ELLNODE *) pEntry);
and the QENTRYs are popped from the queue and processed in seq_pvGetQ() in
seq_if.c
		pEntry = (QENTRY *) ellGet(&pSP->pQueues[pDB->queueIndex]);

		/* If none, "impossible" */
		if (pEntry == NULL)
		{
		...
		}

		/* Extract information from entry (code from seq_ca.c)
		   (pDB changed to refer to channel for which monitor
		   was posted) */
		else
		{
		...
		}		...

However, the QENTRYs are never free'ed.  I have compared this with the code
from v2.0.7 where the else clause ends with

		else
		{
		...
			/* Free queue entry */
			free(pEntry);
		}

I am not sure whether the queues are even supposed to work in v1.9.5, but
this is the only bug I have encountered.  Since it is so easy to fix, it
would be desirable to release one more bug fix for those of us still working
with EPICS R3.13!

Cheers,
Dr. Russell O. Redman
Tel: (250) 363-6917 | Fax: (250) 363-0045
<mailto:[email protected]>
National Research Council Canada | Conseil national de recherches Canada
5071 West Saanich Road           | 5071 West Saanich Road
Victoria, B. C. V9E 2E7          | Victoria, C.-B. V9E 2E7
Government of Canada             | Gouvernement du Canada

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System