diff --git a/src/ioc/db/callback.c b/src/ioc/db/callback.c
index 56a399ff6..897279ff9 100644
--- a/src/ioc/db/callback.c
+++ b/src/ioc/db/callback.c
@@ -54,6 +54,7 @@ typedef struct cbQueueSet {
     epicsEventId semWakeUp;
     epicsRingPointerId queue;
     int queueOverflow;
+    int shutdown;
     int threadsConfigured;
     int threadsRunning;
 } cbQueueSet;
@@ -73,7 +74,6 @@ static epicsTimerQueueId timerQueue;
 enum ctl {ctlInit, ctlRun, ctlPause, ctlExit};
 static volatile enum ctl cbCtl;
 static epicsEventId startStopEvent;
-static void *exitCallback;
 
 /* Static data */
 static char *threadNamePrefix[NUM_CALLBACK_PRIORITIES] = {
@@ -149,12 +149,13 @@ int callbackParallelThreads(int count, const char *prio)
 
 static void callbackTask(void *arg)
 {
-    cbQueueSet *mySet = &callbackQueue[*(int*)arg];
+    int prio = *(int*)arg;
+    cbQueueSet *mySet = &callbackQueue[prio];
 
     taskwdInsert(0, NULL, NULL);
     epicsEventSignal(startStopEvent);
 
-    while(TRUE) {
+    while(!mySet->shutdown) {
         void *ptr;
         if (epicsRingPointerIsEmpty(mySet->queue))
             epicsEventMustWait(mySet->semWakeUp);
@@ -163,39 +164,50 @@ static void callbackTask(void *arg)
             CALLBACK *pcallback = (CALLBACK *)ptr;
             if(!epicsRingPointerIsEmpty(mySet->queue))
                 epicsEventMustTrigger(mySet->semWakeUp);
-            if (ptr == &exitCallback) goto shutdown;
             mySet->queueOverflow = FALSE;
             (*pcallback->callback)(pcallback);
         }
     }
 
-shutdown:
-    mySet->threadsRunning--;
+    if(!epicsAtomicDecrIntT(&mySet->threadsRunning))
+        epicsEventSignal(startStopEvent);
     taskwdRemove(0);
-    epicsEventSignal(startStopEvent);
 }
 
-void callbackShutdown(void)
+void callbackStop(void)
 {
     int i;
 
     if (cbCtl == ctlExit) return;
     cbCtl = ctlExit;
 
-    /* sequential shutdown of workers */
     for (i = 0; i < NUM_CALLBACK_PRIORITIES; i++) {
-        while (callbackQueue[i].threadsRunning) {
-            if(epicsRingPointerPush(callbackQueue[i].queue, &exitCallback)) {
-                epicsEventSignal(callbackQueue[i].semWakeUp);
-                epicsEventWait(startStopEvent);
-            } else {
-                epicsThreadSleep(0.05);
-            }
-        }
-        assert(callbackQueue[i].threadsRunning==0);
-        epicsEventDestroy(callbackQueue[i].semWakeUp);
-        epicsRingPointerDelete(callbackQueue[i].queue);
+        callbackQueue[i].shutdown = 1;
+        epicsEventSignal(callbackQueue[i].semWakeUp);
     }
+
+    for (i = 0; i < NUM_CALLBACK_PRIORITIES; i++) {
+        cbQueueSet *mySet = &callbackQueue[i];
+
+        while (epicsAtomicGetIntT(&mySet->threadsRunning)) {
+            epicsEventSignal(mySet->semWakeUp);
+            epicsEventWaitWithTimeout(startStopEvent, 0.1);
+        }
+    }
+}
+
+void callbackCleanup(void)
+{
+    int i;
+
+    for (i = 0; i < NUM_CALLBACK_PRIORITIES; i++) {
+        cbQueueSet *mySet = &callbackQueue[i];
+
+        assert(epicsAtomicGetIntT(&mySet->threadsRunning)==0);
+        epicsEventDestroy(mySet->semWakeUp);
+        epicsRingPointerDelete(mySet->queue);
+    }
+
     epicsTimerQueueRelease(timerQueue);
     epicsEventDestroy(startStopEvent);
     startStopEvent = NULL;
@@ -239,7 +251,7 @@ void callbackInit(void)
                 cantProceed("Failed to spawn callback thread %s\n", threadName);
             } else {
                 epicsEventWait(startStopEvent);
-                callbackQueue[i].threadsRunning++;
+                epicsAtomicIncrIntT(&callbackQueue[i].threadsRunning);
             }
         }
     }
diff --git a/src/ioc/db/callback.h b/src/ioc/db/callback.h
index 2732f9d5e..096854fb3 100644
--- a/src/ioc/db/callback.h
+++ b/src/ioc/db/callback.h
@@ -57,7 +57,8 @@ typedef void    (*CALLBACKFUNC)(struct callbackPvt*);
 ( (USER) = (void *)((CALLBACK *)(PCALLBACK))->user )
 
 epicsShareFunc void callbackInit(void);
-epicsShareFunc void callbackShutdown(void);
+epicsShareFunc void callbackStop(void);
+epicsShareFunc void callbackCleanup(void);
 epicsShareFunc int callbackRequest(CALLBACK *pCallback);
 epicsShareFunc void callbackSetProcess(
     CALLBACK *pcallback, int Priority, void *pRec);
diff --git a/src/ioc/db/dbScan.c b/src/ioc/db/dbScan.c
index ba927a04b..9c1a1bef9 100644
--- a/src/ioc/db/dbScan.c
+++ b/src/ioc/db/dbScan.c
@@ -151,7 +151,7 @@ static void buildScanLists(void);
 static void addToList(struct dbCommon *precord, scan_list *psl);
 static void deleteFromList(struct dbCommon *precord, scan_list *psl);
 
-void scanShutdown(void)
+void scanStop(void)
 {
     int i;
 
@@ -168,6 +168,10 @@ void scanShutdown(void)
 
     scanOnce((dbCommon *)&exitOnce);
     epicsEventWait(startStopEvent);
+}
+
+void scanCleanup(void)
+{
 
     deletePeriodic();
     ioscanDestroy();
diff --git a/src/ioc/db/dbScan.h b/src/ioc/db/dbScan.h
index cd9666348..769a22893 100644
--- a/src/ioc/db/dbScan.h
+++ b/src/ioc/db/dbScan.h
@@ -46,7 +46,8 @@ struct dbCommon;
 epicsShareFunc long scanInit(void);
 epicsShareFunc void scanRun(void);
 epicsShareFunc void scanPause(void);
-epicsShareFunc void scanShutdown(void);
+epicsShareFunc void scanStop(void);
+epicsShareFunc void scanCleanup(void);
 
 epicsShareFunc EVENTPVT eventNameToHandle(const char* event);
 epicsShareFunc void postEvent(EVENTPVT epvt);
diff --git a/src/ioc/db/test/callbackParallelTest.c b/src/ioc/db/test/callbackParallelTest.c
index eeb6ddaee..6dda789e3 100644
--- a/src/ioc/db/test/callbackParallelTest.c
+++ b/src/ioc/db/test/callbackParallelTest.c
@@ -184,7 +184,8 @@ MAIN(callbackParallelTest)
         free(pcbt[i]);
     }
 
-    callbackShutdown();
+    callbackStop();
+    callbackCleanup();
 
     return testDone();
 }
diff --git a/src/ioc/db/test/callbackTest.c b/src/ioc/db/test/callbackTest.c
index c4c6b31d9..d733f99d7 100644
--- a/src/ioc/db/test/callbackTest.c
+++ b/src/ioc/db/test/callbackTest.c
@@ -181,7 +181,8 @@ MAIN(callbackTest)
         free(pcbt[i]);
     }
 
-    callbackShutdown();
+    callbackStop();
+    callbackCleanup();
 
     return testDone();
 }
diff --git a/src/ioc/misc/iocInit.c b/src/ioc/misc/iocInit.c
index a8dca3c9a..9759ba18f 100644
--- a/src/ioc/misc/iocInit.c
+++ b/src/ioc/misc/iocInit.c
@@ -607,7 +607,8 @@ static void initialProcess(void)
 
 
 /*
- * Shutdown processing.
+ * set DB_LINK and CA_LINK to PV_LINK
+ * Delete record scans
  */
 static void doCloseLinks(dbRecordType *pdbRecordType, dbCommon *precord,
     void *user)
@@ -678,8 +679,12 @@ int iocShutdown(void)
     if (iocState == iocVirgin || iocState == iocStopped) return 0;
     iterateRecords(doCloseLinks, NULL);
     if (iocBuildMode==buildIsolated) {
-        scanShutdown();
-        callbackShutdown();
+        /* stop and "join" threads */
+        scanStop();
+        callbackStop();
+        /* free resources */
+        scanCleanup();
+        callbackCleanup();
         iterateRecords(doFreeRecord, NULL);
         dbLockCleanupRecords(pdbbase);
         asShutdown();