Linux 内核延时

内核延时
10.6.1 短延时
纳秒、微秒、毫秒延时(无谓耗费CPU资源)
void ndelay(unsigned long nsecs);
void udelay(unsigned long usecs);
void mdelay(unsigned long msecs);


对于毫秒级以上时延内核提供以下函数
void msleep(unsigned int millisecs);
unsigned long msleep_interruptible(unsigned int millisecs);
void ssleep(unsigned int seconds);


长延时
//延时100个jiffies;
unsigned long delay = jiffies + 100;
while(time_before(jiffies, delay));


//再延时2s
unsigned long delay = jiffes + 2*HZ;
while (time_before(jiffes, delay));


//jiffies
unsigned long msecs_to_jiffies(const unsigned int m)
unsigned long usecs_to_jiffies(const unsigned int u)




10.6.3 睡着延迟
schedule_timeout()


/////////////////////////////////////////////////////////////
//
linux/rtc.h
extern int rtc_month_days(unsigned int month, unsigned int year);
extern int rtc_year_days(unsigned int day, unsigned int month, unsigned int year);
extern int rtc_valid_tm(struct rtc_time *tm);
extern int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time);
extern void rtc_time_to_tm(unsigned long time, struct rtc_time *tm);


extern int rtc_read_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern int rtc_set_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern int rtc_initialize_alarm(struct rtc_device *rtc,
struct rtc_wkalrm *alrm);
extern void rtc_update_irq(struct rtc_device *rtc,
unsigned long num, unsigned long events);






linux/time.h


extern void do_gettimeofday(struct timeval *tv);
extern int do_settimeofday(const struct timespec *tv);
extern int do_sys_settimeofday(const struct timespec *tv,
      const struct timezone *tz);
#define do_posix_clock_monotonic_gettime(ts) ktime_get_ts(ts)
extern long do_utimes(int dfd, const char __user *filename, struct timespec *times, int flags);
struct itimerval;
extern int do_setitimer(int which, struct itimerval *value,
struct itimerval *ovalue);
extern unsigned int alarm_setitimer(unsigned int seconds);
extern int do_getitimer(int which, struct itimerval *value);
extern int __getnstimeofday(struct timespec *tv);
extern void getnstimeofday(struct timespec *tv);
extern void getrawmonotonic(struct timespec *ts);
extern void getnstime_raw_and_real(struct timespec *ts_raw,
struct timespec *ts_real);
extern void getboottime(struct timespec *ts);
extern void monotonic_to_bootbased(struct timespec *ts);
extern void get_monotonic_boottime(struct timespec *ts);


extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
extern u64 timekeeping_max_deferment(void);
extern int timekeeping_inject_offset(struct timespec *ts);
extern s32 timekeeping_get_tai_offset(void);
extern void timekeeping_set_tai_offset(s32 tai_offset);
extern void timekeeping_clocktai(struct timespec *ts);


struct tms;

extern void do_sys_times(struct tms *);