Linux: sched: might_sleep； 一个调试函数，演变为真实的睡眠函数，实至名归
#define might_sleep() do { might_resched(); } while (0)
#ifdef CONFIG_PREEMPT_VOLUNTARY
extern int _cond_resched(void);
# define might_resched() _cond_resched(
#define might_sleep() do { might_resched(); } while (0)
#ifdef CONFIG_PREEMPT_VOLUNTARY
extern int _cond_resched(void);
# define might_resched() _cond_resched(