fixed race condition

src/db/dbServiceIO.cpp

@@ -173,7 +173,7 @@ void dbServiceIO::callStateNotify ( struct dbAddr & addr,
     if ( status ) {
         notify.exception ( ECA_GETFAIL, 
             "db_get_field() completed unsuccessfuly",
-            type, count);
+            type, count );
     }
     else { 
         notify.current ( type, count, this->pEventCallbackCache );
@@ -186,8 +186,8 @@ extern "C" void cacAttachClientCtx ( void * pPrivate )
     assert ( status == ECA_NORMAL );
 }
 
-dbEventSubscription dbServiceIO::subscribe ( struct dbAddr &addr, dbChannelIO &chan,
-             dbSubscriptionIO &subscr, unsigned mask, cacChannel::ioid *pId )
+dbEventSubscription dbServiceIO::subscribe ( struct dbAddr & addr, dbChannelIO & chan,
+             dbSubscriptionIO & subscr, unsigned mask )
 {
     dbEventSubscription es;
     int status;
@@ -220,19 +220,12 @@ dbEventSubscription dbServiceIO::subscribe ( struct dbAddr &addr, dbChannelIO &c
 
     es = db_add_event ( this->ctx, &addr,
         dbSubscriptionEventCallback, (void *) &subscr, mask );
-    if ( es ) {
-        db_post_single_event ( es );
-    }
-    else {
+    if ( ! es ) {
         epicsAutoMutex locker ( this->mutex );
         chan.dbServicePrivateListOfIO::eventq.remove ( subscr );
         this->ioTable.remove ( subscr );
     }
 
-    if ( pId ) {
-        *pId = subscr.getId ();
-    }
-
     return es;
 }
 

src/db/dbSubscriptionIO.cpp

@@ -36,14 +36,20 @@ epicsMutex dbSubscriptionIO::freeListMutex;
 dbSubscriptionIO::dbSubscriptionIO ( dbServiceIO &serviceIO, dbChannelIO &chanIO, 
     dbAddr &addr, cacStateNotify &notifyIn, 
     unsigned typeIn, unsigned long countIn, unsigned maskIn,
-    cacChannel::ioid * pId ) :
+        cacChannel::ioid * pId ) :
     notify ( notifyIn ), chan ( chanIO ), es ( 0 ), 
         type ( typeIn ), count ( countIn ), id ( 0u )
 {
-    this->es = serviceIO.subscribe ( addr, chanIO, *this, maskIn, pId );
+    this->es = serviceIO.subscribe ( addr, chanIO, *this, maskIn );
     if ( ! this->es ) {
         throw std::bad_alloc ();
     }
+
+    if ( pId ) {
+        *pId = this->getId ();
+    }
+
+    db_post_single_event ( this->es );
 }
 
 dbSubscriptionIO::~dbSubscriptionIO ()