Linux源码阅读笔记10-进程NICE案例分析2

void set_user_nice(struct task_struct *p, long nice)
{
  bool queued, running;
  int old_prio;
  struct rq_flags rf;
  struct rq *rq;
  if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
    return;
  /*
   * We have to be careful, if called from sys_setpriority(),
   * the task might be in the middle of scheduling on another CPU.
   */
  rq = task_rq_lock(p, &rf);
  update_rq_clock(rq);
  /*
   * The RT priorities are set via sched_setscheduler(), but we still
   * allow the 'normal' nice value to be set - but as expected
   * it wont have any effect on scheduling until the task is
   * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
   */
  if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
    p->static_prio = NICE_TO_PRIO(nice);
    goto out_unlock;
  }
  queued = task_on_rq_queued(p);
  running = task_current(rq, p);
  if (queued)
    dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
  if (running)
    put_prev_task(rq, p);
  p->static_prio = NICE_TO_PRIO(nice);
  set_load_weight(p, true);
  old_prio = p->prio;
  p->prio = effective_prio(p);
  if (queued)
    enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
  if (running)
    set_next_task(rq, p);
  /*
   * If the task increased its priority or is running and
   * lowered its priority, then reschedule its CPU:
   */
  p->sched_class->prio_changed(rq, p, old_prio);
out_unlock:
  task_rq_unlock(rq, p, &rf);
}
EXPORT_SYMBOL(set_user_nice);

#include <linux/module.h>
#include <linux/pid.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kthread.h>
static int MyThreadFunc(void* argc) {
  printk("Prompt:kernel thread PID : %d.\n", current->pid);
  printk("Prompt:kernel thread static_prio : %d.\n", current->static_prio);
  printk("Prompt:kernel thread nice : %d.\n", task_nice(current));
  return 0;
}
static int __init SetUserNiceInit(void) {
  struct task_struct* new_task = NULL;
  new_task = kthread_create_on_node(MyThreadFunc, NULL, -1, "setusernice.c");
  printk("Prompt:new thread nice : %d.\n", task_nice(new_task));
  printk("Prompt:new thread static_prio : %d.\n", new_task->static_prio);
  printk("Prompt:new thread prio : %d.\n", new_task->prio);
  set_user_nice(new_task, 16);
  printk("Prompt:new thread nice : %d.\n", task_nice(new_task));
  printk("Prompt:new thread static_prio : %d.\n", new_task->static_prio);
  printk("Prompt:new thread prio : %d.\n", new_task->prio);
  return 0;
}
static void __exit SetUserNiceExit(void) {
  printk("Prompt:exit kernel.\n");
}
module_init(SetUserNiceInit);
module_exit(SetUserNiceExit);