Can s-function run in simulink REAL-TIME model?

I am running the PMSM block and the S-function block (sfun_pwm) in a Simulink REAL-TIME model, and the solver of the model is a fixed step. An error occurs.

Block 'PWMSfunction1/S-Function' has a controllable sample time, but the model 'PWMSfunction1' is not using single tasking mode. Currently, controllable sample times can only be used in single tasking mode.