What's the correct scheduling of calling C functions of a Simulink model after Simulink Coder conversion?

I've used Simulink to build a subsystem and converted it into C using Simulink Coder. Then I will write my main function where the subsystem's C functions (mdlOutput(), mdlUpdate(), etc) will be called, as follows:

/* scheduling 1*/
main()
{
...  
for (i=0;i<100;i++)
{
   mdlOutput();
   mdl_U = 1-mdl_Y; /* updating input using output */
   mdlUpdate();
}
...
}

You can see that a feedback is formed in the main function. However, I've seen many examples where mdl_U is put ahead of mdlOuput(), like:

/* scheduling 2*/
main()
{
...
for (i=0;i<100;i++)
{
   mdl_U = 1-mdl_Y; /* updating input using output */
   mdlOutput();  
   mdlUpdate();
 }
...
}

Above two schedulings give different results. I'm wondering which one is correct? Many thanks for any help.