struct task_struct {...int prio, static_prio, normal_prio;unsigned int rt_priority;...
}

/* linux-kernel 2.6.34 /include/linux/sched.h *//** Priority of a process goes from 0..MAX_PRIO-1, valid RT* priority is 0..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH* tasks are in the range MAX_RT_PRIO..MAX_PRIO-1. Priority* values are inverted: lower p->prio value means higher priority.** The MAX_USER_RT_PRIO value allows the actual maximum* RT priority to be separate from the value exported to* user-space.  This allows kernel threads to set their* priority to a value higher than any user task. Note:* MAX_RT_PRIO must not be smaller than MAX_USER_RT_PRIO.*/#define MAX_USER_RT_PRIO     100
#define MAX_RT_PRIO          MAX_USER_RT_PRIO#define MAX_PRIO            (MAX_RT_PRIO + 40)
#define DEFAULT_PRIO        (MAX_RT_PRIO + 20)　　　　// 默认优先级，对应 nice 值为 0 的静态优先级

/* linux-kernel 2.6.34  /kernel/sched.c  */#include "sched_idletask.c"
#include "sched_fair.c"
#include "sched_rt.c"
#ifdef CONFIG_SCHED_DEBUG
#include "sched_debug.c"
#endif/** __normal_prio - return the priority that is based on the static prio*/
static inline int __normal_prio(struct task_struct *p)　　　　// _normal_prio 函数，返回静态优先级值
{return p->static_prio;
}/** Calculate the expected normal priority: i.e. priority* without taking RT-inheritance into account. Might be* boosted by interactivity modifiers. Changes upon fork,* setprio syscalls, and whenever the interactivity* estimator recalculates.*/
static inline int normal_prio(struct task_struct *p)　　　　// normal_prio 函数
{int prio;if (task_has_rt_policy(p))　　　　　　　　　　　　　　　　　// task_has_rt_policy 函数，判断进程是否为实时进程，若为实时进程，则返回1，否则返回0prio = MAX_RT_PRIO-1 - p->rt_priority;　　　　　　　 // 进程为实时进程，prio 值为实时优先级值做相关运算得到： prio = MAX_RT_PRIO -1 - p->rt_priorityelseprio = __normal_prio(p);　　　　　　　　　　　　　　　　// 进程为非实时进程，则 prio 值为静态优先级值，即 prio = p->static_prioreturn prio;
}/** Calculate the current priority, i.e. the priority* taken into account by the scheduler. This value might* be boosted by RT tasks, or might be boosted by* interactivity modifiers. Will be RT if the task got* RT-boosted. If not then it returns p->normal_prio.*/
static int effective_prio(struct task_struct *p)　　　　　　　// effective_prio 函数，计算进程的有效优先级，即prio值，这个值是最终调度器所使用的优先级值
{p->normal_prio = normal_prio(p);　　　　　　　　　　　　　　// 计算 normal_prio 的值/** If we are RT tasks or we were boosted to RT priority,* keep the priority unchanged. Otherwise, update priority* to the normal priority:*/if (!rt_prio(p->prio))return p->normal_prio;　　　　　　　　　　　　　　　　　　// 若进程是非实时进程，则返回 normal_prio 值，这时的 normal_prio = static_prioreturn p->prio;　　　　　　　　　　　　　　　　　　　　　　　　 // 否则，返回值不变，依然为 prio 值，此时 prio = MAX_RT_PRIO -1 - p->rt_priority
} /*********************** 函数 set_user_nice ****************************************/
void set_user_nice(struct task_struct *p, long nice)
{....p->prio = effective_prio(p);　　　　　　　　　　　　　　     // 在函数 set_user_nice 中，调用 effective_prio 函数来设置进程的 prio 值
　　　　　....
}

/** Convert user-nice values [ -20 ... 0 ... 19 ]* to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],* and back.*/
#define NICE_TO_PRIO(nice)    (MAX_RT_PRIO + (nice) + 20)
#define PRIO_TO_NICE(prio)    ((prio) - MAX_RT_PRIO - 20)
#define TASK_NICE(p)        PRIO_TO_NICE((p)->static_prio)/** 'User priority' is the nice value converted to something we* can work with better when scaling various scheduler parameters,* it's a [ 0 ... 39 ] range.*/
#define USER_PRIO(p)        ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p)    USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO        (USER_PRIO(MAX_PRIO))/********************* 函数 set_user_nice *****************************/
p->static_prio = NICE_TO_PRIO(nice);    　　　　// 当有需要时，系统会通过调用 NICE_TO_PRIO() 来修改 static_prio 的值

static inline int normal_prio(struct task_struct *p)　　　　// normal_prio 函数
{int prio;if (task_has_rt_policy(p))　　　　　　　　　　　　　　　　　// task_has_rt_policy 函数，判断进程是否为实时进程，若为实时进程，则返回1，否则返回0prio = MAX_RT_PRIO-1 - p->rt_priority;　　　　　　　 // 进程为实时进程，prio 值为实时优先级值做相关运算得到： prio = MAX_RT_PRIO -1 - p->rt_priorityelseprio = __normal_prio(p);　　　　　　　　　　　　　　　　// 进程为非实时进程，则 prio 值为静态优先级值，即 prio = p->static_prioreturn prio;
}