On Alpha and Integrity server systems, allows modification of the
    CPU affinity set for a specified kernel thread.

    This service accepts 64-bit addresses.

    Format

      SYS$PROCESS_AFFINITY  [pidadr], [prcnam], [select_mask],

                            [modify_mask], [prev_mask], [flags]

                            [,[mask_length]]

    C Prototype

      int sys$process_affinity  (unsigned int *pidadr, void *prcnam,

                                struct _generic_64 *select_mask,

                                struct _generic_64 *modify_mask,

                                struct _generic_64 *prev_mask, struct

                                _generic_64 *flags,...);