Listing 2. struct root_domain

struct root_domain {
    atomic_t   refcount;  /* reference count for the domain */
    cpumask_t  span;      /* span of member cpus of the domain*/
    cpumask_t  online;    /* number of online cpus in the domain*/
    cpumask_t  rto_mask;  /* mask of overloaded cpus in the domain*/
    atomic_t   rto_count; /* number of overloaded cpus */
   ....
};