小编goo*_*sse的帖子

stop_sched_class在Kernel中有什么用？在pick_next_task功能上，调度程序将首先选择下一个任务stop_sched_class。我sched_class为内核删除此文件有什么问题吗？

#define for_each_class(class) \
   for (class = sched_class_highest; class; class = class->next)


#define sched_class_highest (&stop_sched_class)
extern const struct sched_class stop_sched_class;

/*
 * Simple, special scheduling class for the per-CPU stop tasks:
*/
const struct sched_class stop_sched_class = {
   .next                   = &rt_sched_class,

   .enqueue_task           = enqueue_task_stop,
   .dequeue_task           = dequeue_task_stop,
   .yield_task             = yield_task_stop,

   .check_preempt_curr     = check_preempt_curr_stop,

   .pick_next_task         = pick_next_task_stop,
   .put_prev_task          = put_prev_task_stop,

 #ifdef CONFIG_SMP
   .select_task_rq         = select_task_rq_stop,
 #endif

  .set_curr_task          = set_curr_task_stop,
  .task_tick              = task_tick_stop,

  .get_rr_interval        = …

CPU何时以及如何从内核模式切换到用户模式在X86上:它到底是做什么用的？它是如何实现这种转变的？