Fix idleness computation when pipeline length is 0

src/drivers/cuda/driver_cuda.c

@@ -753,7 +753,7 @@ int _starpu_cuda_driver_run_once(struct _starpu_worker_set *worker_set)
 #endif
 		}
 
-		if (worker->ntasks < worker->pipeline_length)
+		if (!worker->pipeline_length || worker->ntasks < worker->pipeline_length)
 			idle++;
 	}
 

src/drivers/opencl/driver_opencl.c

@@ -733,7 +733,7 @@ int _starpu_opencl_driver_run_once(struct _starpu_worker *worker)
 			_STARPU_TRACE_END_EXECUTING();
 		}
 	}
-	if (worker->ntasks < worker->pipeline_length)
+	if (!worker->pipeline_length || worker->ntasks < worker->pipeline_length)
 		idle++;
 
 #if defined(STARPU_NON_BLOCKING_DRIVERS) && !defined(STARPU_SIMGRID)