用户空间:
#include <unistd.h>
1、unsigned int sleep(unsigned int seconds);
秒级
2、int usleep(useconds_t usec);
微秒级
内核空间:
include <linux/delay.h>
1、void ndelay(unsigned long nsecs);
纳秒级
2、void udelay(unsigned long usecs);
微秒级
3、void mdelay(unsigned long msecs);
毫秒级