The following code produces exceptions as below in bursts after a few seconds. More generally, it seems Delay starts failing in situations where the system is somewhat loaded (such as during the event- and render-loops in our SDL/cairo bindings-in-progress).

Code:

Object subclass: DelayExperiment [
    run [
        [ (Delay forMilliseconds: 1) wait ] repeat.
    ]
].
DelayExperiment new run.

Expected output: nothing, forever.

Actual output:

$ gst delay-bug.st 
"Global garbage collection... done"
Object: nil error: did not understand #goodness:
MessageNotUnderstood(Exception)>>signal
UndefinedObject(Object)>>doesNotUnderstand: #goodness:
optimized [] in BlockClosure class>>exceptionHandlerSearchBlock
[] in Kernel.CoreException>>instantiateNextHandler:
MethodContext(ContextPart)>>scanBacktraceForAttribute:do:
Kernel.CoreException>>instantiateNextHandler:
SystemExceptions.PrimitiveFailed(Exception)>>signal
SystemExceptions.PrimitiveFailed class(Exception class)>>signal
ProcessorScheduler(Object)>>primitiveFailed
ProcessorScheduler>>signal:atMilliseconds:
Delay class>>handleDelayEvent
optimized [] in Delay class>>runDelayProcess
[] in BlockClosure>>ifCurtailed:
BlockClosure>>ensure:
BlockClosure>>ifCurtailed:
Delay class>>runDelayProcess
optimized [] in Delay class>>startDelayLoop
[] in Process>>onBlock:at:suspend:
BlockClosure>>on:do:
[] in Process>>onBlock:at:suspend:
BlockClosure>>ensure:
[] in Process>>onBlock:at:suspend:
[] in BlockClosure>>asContext:
BlockContext class>>fromClosure:parent:
Object: ProcessorScheduler new "<0x4030c820>" error: primitive operation failed
SystemExceptions.PrimitiveFailed(Exception)>>signal
SystemExceptions.PrimitiveFailed class(Exception class)>>signal
ProcessorScheduler(Object)>>primitiveFailed
ProcessorScheduler>>signal:atMilliseconds:
Delay class>>handleDelayEvent
optimized [] in Delay class>>runDelayProcess
[] in BlockClosure>>ifCurtailed:
BlockClosure>>ensure:
BlockClosure>>ifCurtailed:
Delay class>>runDelayProcess
optimized [] in Delay class>>startDelayLoop
[] in Process>>onBlock:at:suspend:
BlockClosure>>on:do:
[] in Process>>onBlock:at:suspend:
BlockClosure>>ensure:
[] in Process>>onBlock:at:suspend:
[] in BlockClosure>>asContext:
BlockContext class>>fromClosure:parent:
Object: ProcessorScheduler new "<0x4030c820>" error: primitive operation failed
SystemExceptions.PrimitiveFailed(Exception)>>signal
SystemExceptions.PrimitiveFailed class(Exception class)>>signal
ProcessorScheduler(Object)>>primitiveFailed
ProcessorScheduler>>signal:atMilliseconds:
Delay class>>handleDelayEvent
optimized [] in Delay class>>runDelayProcess
[] in BlockClosure>>ifCurtailed:
BlockClosure>>ensure:
BlockClosure>>ifCurtailed:
Delay class>>runDelayProcess
optimized [] in Delay class>>startDelayLoop
[] in Process>>onBlock:at:suspend:
BlockClosure>>on:do:
[] in Process>>onBlock:at:suspend:
BlockClosure>>ensure:
[] in Process>>onBlock:at:suspend:
[] in BlockClosure>>asContext:
BlockContext class>>fromClosure:parent:
Object: ProcessorScheduler new "<0x4030c820>" error: primitive operation failed
SystemExceptions.PrimitiveFailed(Exception)>>signal
SystemExceptions.PrimitiveFailed class(Exception class)>>signal
ProcessorScheduler(Object)>>primitiveFailed
ProcessorScheduler>>signal:atMilliseconds:
Delay class>>handleDelayEvent
optimized [] in Delay class>>runDelayProcess
[] in BlockClosure>>ifCurtailed:
BlockClosure>>ensure:
BlockClosure>>ifCurtailed:
Delay class>>runDelayProcess
optimized [] in Delay class>>startDelayLoop
[] in Process>>onBlock:at:suspend:
BlockClosure>>on:do:
[] in Process>>onBlock:at:suspend:
BlockClosure>>ensure:
[] in Process>>onBlock:at:suspend:
[] in BlockClosure>>asContext:
BlockContext class>>fromClosure:parent:
...
...
...

         _gst_enable_interrupts ();
       }
      else

    }

  UNPOP (2);

diff --git a/libgst/prims.def b/libgst/prims.def
index 745d902..a243af4 100644
--- a/libgst/prims.def
+++ b/libgst/prims.def
@@ -3000,10 +3000,8 @@ primitive VMpr_Processor_signalAtMilliseconds [succeed,fail,check_interrupt]
          _gst_enable_interrupts ();
        }
       else
-       {
-         _gst_async_timed_wait (oop1, arg2);
-         PRIM_SUCCEEDED;
-       }
+       _gst_async_timed_wait (oop1, arg2);
+      PRIM_SUCCEEDED;
     }
 
   UNPOP (2);