Multi-core CPUs and OS schedulers

[K.I.L.E.R]

I want to clear this up ASAP.
When programs are executed on a multi core system, are they really assigned a CPU by the OS scheduler? Is there a scheduler for each core?

I believed that a program will get a time slice of the next available CPU, that would be determined by a data structure that would auto-sort based on how busy each core would be.

 

[Humus]

Unless the process has an affinity mask it can run on any core at any timeslice on the discretion of the OS. It's not uncommon that a process jumps back and forth between different cores.

 

[K.I.L.E.R]

Thanks.

Could an affinity mask even be set for a multi-core cpu? I'm under the assumption that the number of cores are invisible to the OS on the scheduling level.