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current_kernel_time

struct timespec current_kernel_time(void){    struct timespec now;    unsigned long seq;    do {        seq = read_seqbegin(&xtime_lock);        now = xtime;    } while (read_seqretry(&xtime_lock, seq));    return now;}

do_gettimeofday

struct timespec {    __kernel_time_t tv_sec;         /* seconds */    long        tv_nsec;        /* nanoseconds */};void do_gettimeofday(struct timeval *tv){    struct timespec now;    getnstimeofday(&now);    tv->tv_sec = now.tv_sec;    tv->tv_usec = now.tv_nsec/1000;}void getnstimeofday(struct timespec *ts){    unsigned long seq;    s64 nsecs;    WARN_ON(timekeeping_suspended);    do {        seq = read_seqbegin(&xtime_lock);        *ts = xtime;        nsecs = timekeeping_get_ns();        /* If arch requires, add in gettimeoffset() */        nsecs += arch_gettimeoffset();    } while (read_seqretry(&xtime_lock, seq));    timespec_add_ns(ts, nsecs);}

rtc_time_to_tm

struct rtc_time {    int tm_sec;    int tm_min;    int tm_hour;    int tm_mday;    int tm_mon;    int tm_year;    int tm_wday;    int tm_yday;    int tm_isdst;};int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time){    *time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,            tm->tm_hour, tm->tm_min, tm->tm_sec);    return 0;}

rtc_time_to_tm

void rtc_time_to_tm(unsigned long time, struct rtc_time *tm){    unsigned int month, year;    int days;    days = time / 86400;    time -= (unsigned int) days * 86400;    /* day of the week, 1970-01-01 was a Thursday */    tm->tm_wday = (days + 4) % 7;    year = 1970 + days / 365;    days -= (year - 1970) * 365        + LEAPS_THRU_END_OF(year - 1)        - LEAPS_THRU_END_OF(1970 - 1);    if (days < 0) {        year -= 1;        days += 365 + is_leap_year(year);    }    tm->tm_year = year - 1900;    tm->tm_yday = days + 1;    for (month = 0; month < 11; month++) {        int newdays;        newdays = days - rtc_month_days(month, year);        if (newdays < 0)            break;        days = newdays;    }    tm->tm_mon = month;    tm->tm_mday = days + 1;    tm->tm_hour = time / 3600;    time -= tm->tm_hour * 3600;    tm->tm_min = time / 60;    tm->tm_sec = time - tm->tm_min * 60;}