time.h

来自「Linux Kernel 2.6.9 for OMAP1710」· C头文件 代码 · 共 429 行

#ifndef _LINUX_TIME_H
#define _LINUX_TIME_H

#include <asm/param.h>
#include <linux/types.h>

#ifndef _STRUCT_TIMESPEC
#define _STRUCT_TIMESPEC
struct timespec {
	time_t	tv_sec;		/* seconds */
	long	tv_nsec;	/* nanoseconds */
};
#endif /* _STRUCT_TIMESPEC */

struct timeval {
	time_t		tv_sec;		/* seconds */
	suseconds_t	tv_usec;	/* microseconds */
};

struct timezone {
	int	tz_minuteswest;	/* minutes west of Greenwich */
	int	tz_dsttime;	/* type of dst correction */
};

#ifdef __KERNEL__

#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/timex.h>
#include <asm/div64.h>
#ifndef div_long_long_rem

#define div_long_long_rem(dividend,divisor,remainder) ({ \
		       u64 result = dividend;		\
		       *remainder = do_div(result,divisor); \
		       result; })

#endif

/*
 * Have the 32 bit jiffies value wrap 5 minutes after boot
 * so jiffies wrap bugs show up earlier.
 */
#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))

/*
 * Change timeval to jiffies, trying to avoid the
 * most obvious overflows..
 *
 * And some not so obvious.
 *
 * Note that we don't want to return MAX_LONG, because
 * for various timeout reasons we often end up having
 * to wait "jiffies+1" in order to guarantee that we wait
 * at _least_ "jiffies" - so "jiffies+1" had better still
 * be positive.
 */
#define MAX_JIFFY_OFFSET ((~0UL >> 1)-1)

/* Parameters used to convert the timespec values */
#ifndef USEC_PER_SEC
#define USEC_PER_SEC (1000000L)
#endif

#ifndef NSEC_PER_SEC
#define NSEC_PER_SEC (1000000000L)
#endif

#ifndef NSEC_PER_USEC
#define NSEC_PER_USEC (1000L)
#endif

/*
 * We want to do realistic conversions of time so we need to use the same
 * values the update wall clock code uses as the jiffies size.  This value
 * is: TICK_NSEC (which is defined in timex.h).  This
 * is a constant and is in nanoseconds.  We will used scaled math
 * with a set of scales defined here as SEC_JIFFIE_SC,  USEC_JIFFIE_SC and
 * NSEC_JIFFIE_SC.  Note that these defines contain nothing but
 * constants and so are computed at compile time.  SHIFT_HZ (computed in
 * timex.h) adjusts the scaling for different HZ values.

 * Scaled math???  What is that?
 *
 * Scaled math is a way to do integer math on values that would,
 * otherwise, either overflow, underflow, or cause undesired div
 * instructions to appear in the execution path.  In short, we "scale"
 * up the operands so they take more bits (more precision, less
 * underflow), do the desired operation and then "scale" the result back
 * by the same amount.  If we do the scaling by shifting we avoid the
 * costly mpy and the dastardly div instructions.

 * Suppose, for example, we want to convert from seconds to jiffies
 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE.  The
 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
 * might calculate at compile time, however, the result will only have
 * about 3-4 bits of precision (less for smaller values of HZ).
 *
 * So, we scale as follows:
 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
 * Then we make SCALE a power of two so:
 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
 * Now we define:
 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
 * jiff = (sec * SEC_CONV) >> SCALE;
 *
 * Often the math we use will expand beyond 32-bits so we tell C how to
 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
 * which should take the result back to 32-bits.  We want this expansion
 * to capture as much precision as possible.  At the same time we don't
 * want to overflow so we pick the SCALE to avoid this.  In this file,
 * that means using a different scale for each range of HZ values (as
 * defined in timex.h).
 *
 * For those who want to know, gcc will give a 64-bit result from a "*"
 * operator if the result is a long long AND at least one of the
 * operands is cast to long long (usually just prior to the "*" so as
 * not to confuse it into thinking it really has a 64-bit operand,
 * which, buy the way, it can do, but it take more code and at least 2
 * mpys).

 * We also need to be aware that one second in nanoseconds is only a
 * couple of bits away from overflowing a 32-bit word, so we MUST use
 * 64-bits to get the full range time in nanoseconds.

 */

/*
 * Here are the scales we will use.  One for seconds, nanoseconds and
 * microseconds.
 *
 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
 * check if the sign bit is set.  If not, we bump the shift count by 1.
 * (Gets an extra bit of precision where we can use it.)
 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
 * Haven't tested others.

 * Limits of cpp (for #if expressions) only long (no long long), but
 * then we only need the most signicant bit.
 */

#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
#undef SEC_JIFFIE_SC
#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
#endif
#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
                                TICK_NSEC -1) / (u64)TICK_NSEC))

#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
                                        TICK_NSEC -1) / (u64)TICK_NSEC))
#define USEC_CONVERSION  \
                    ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
                                        TICK_NSEC -1) / (u64)TICK_NSEC))
/*
 * USEC_ROUND is used in the timeval to jiffie conversion.  See there
 * for more details.  It is the scaled resolution rounding value.  Note
 * that it is a 64-bit value.  Since, when it is applied, we are already
 * in jiffies (albit scaled), it is nothing but the bits we will shift
 * off.
 */
#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
/*
 * The maximum jiffie value is (MAX_INT >> 1).  Here we translate that
 * into seconds.  The 64-bit case will overflow if we are not careful,
 * so use the messy SH_DIV macro to do it.  Still all constants.
 */
#if BITS_PER_LONG < 64
# define MAX_SEC_IN_JIFFIES \
	(long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
#else	/* take care of overflow on 64 bits machines */
# define MAX_SEC_IN_JIFFIES \
	(SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)

#endif

/*
 * Convert jiffies to milliseconds and back.
 *
 * Avoid unnecessary multiplications/divisions in the
 * two most common HZ cases:
 */
static inline unsigned int jiffies_to_msecs(const unsigned long j)
{
#if HZ <= 1000 && !(1000 % HZ)
	return (1000 / HZ) * j;
#elif HZ > 1000 && !(HZ % 1000)
	return (j + (HZ / 1000) - 1)/(HZ / 1000);
#else
	return (j * 1000) / HZ;
#endif
}

static inline unsigned int jiffies_to_usecs(const unsigned long j)
{
#if HZ <= 1000 && !(1000 % HZ)
	return (1000000 / HZ) * j;
#elif HZ > 1000 && !(HZ % 1000)
	return (j*1000 + (HZ - 1000))/(HZ / 1000);
#else
	return (j * 1000000) / HZ;
#endif
}

static inline unsigned long msecs_to_jiffies(const unsigned int m)
{
	if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
		return MAX_JIFFY_OFFSET;
#if HZ <= 1000 && !(1000 % HZ)
	return (m + (1000 / HZ) - 1) / (1000 / HZ);
#elif HZ > 1000 && !(HZ % 1000)
	return m * (HZ / 1000);
#else
	return (m * HZ + 999) / 1000;
#endif
}

/*
 * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
 * that a remainder subtract here would not do the right thing as the
 * resolution values don't fall on second boundries.  I.e. the line:
 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
 *
 * Rather, we just shift the bits off the right.
 *
 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
 * value to a scaled second value.
 */
static __inline__ unsigned long
timespec_to_jiffies(const struct timespec *value)
{
	unsigned long sec = value->tv_sec;
	long nsec = value->tv_nsec + TICK_NSEC - 1;

	if (sec >= MAX_SEC_IN_JIFFIES){
		sec = MAX_SEC_IN_JIFFIES;
		nsec = 0;
	}
	return (((u64)sec * SEC_CONVERSION) +
		(((u64)nsec * NSEC_CONVERSION) >>
		 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;

}

static __inline__ void
jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
{
	/*
	 * Convert jiffies to nanoseconds and separate with
	 * one divide.
	 */
	u64 nsec = (u64)jiffies * TICK_NSEC; 
	value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
}

/* Same for "timeval"
 *
 * Well, almost.  The problem here is that the real system resolution is
 * in nanoseconds and the value being converted is in micro seconds.
 * Also for some machines (those that use HZ = 1024, in-particular),
 * there is a LARGE error in the tick size in microseconds.

 * The solution we use is to do the rounding AFTER we convert the
 * microsecond part.  Thus the USEC_ROUND, the bits to be shifted off.
 * Instruction wise, this should cost only an additional add with carry
 * instruction above the way it was done above.
 */
static __inline__ unsigned long
timeval_to_jiffies(const struct timeval *value)
{
	unsigned long sec = value->tv_sec;
	long usec = value->tv_usec;

	if (sec >= MAX_SEC_IN_JIFFIES){
		sec = MAX_SEC_IN_JIFFIES;
		usec = 0;
	}
	return (((u64)sec * SEC_CONVERSION) +
		(((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
		 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
}

static __inline__ void
jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
{
	/*
	 * Convert jiffies to nanoseconds and separate with
	 * one divide.
	 */
	u64 nsec = (u64)jiffies * TICK_NSEC; 
	value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_usec);
	value->tv_usec /= NSEC_PER_USEC;
}

static __inline__ int timespec_equal(struct timespec *a, struct timespec *b) 
{ 
	return (a->tv_sec == b->tv_sec) && (a->tv_nsec == b->tv_nsec);
} 

/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 *
 * [For the Julian calendar (which was used in Russia before 1917,
 * Britain & colonies before 1752, anywhere else before 1582,
 * and is still in use by some communities) leave out the
 * -year/100+year/400 terms, and add 10.]
 *
 * This algorithm was first published by Gauss (I think).
 *
 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 * machines were long is 32-bit! (However, as time_t is signed, we
 * will already get problems at other places on 2038-01-19 03:14:08)
 */
static inline unsigned long
mktime (unsigned int year, unsigned int mon,
	unsigned int day, unsigned int hour,
	unsigned int min, unsigned int sec)
{
	if (0 >= (int) (mon -= 2)) {	/* 1..12 -> 11,12,1..10 */
		mon += 12;		/* Puts Feb last since it has leap day */
		year -= 1;
	}

	return (((
		(unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
			year*365 - 719499
	    )*24 + hour /* now have hours */
	  )*60 + min /* now have minutes */
	)*60 + sec; /* finally seconds */
}

extern struct timespec xtime;
extern struct timespec wall_to_monotonic;
extern seqlock_t xtime_lock;

static inline unsigned long get_seconds(void)
{ 
	return xtime.tv_sec;
}

struct timespec current_kernel_time(void);

#define CURRENT_TIME (current_kernel_time())

#endif /* __KERNEL__ */

#define NFDBITS			__NFDBITS

#ifdef __KERNEL__
extern void do_gettimeofday(struct timeval *tv);
extern int do_settimeofday(struct timespec *tv);
extern int do_sys_settimeofday(struct timespec *tv, struct timezone *tz);
extern void clock_was_set(void); // call when ever the clock is set
extern int do_posix_clock_monotonic_gettime(struct timespec *tp);
extern long do_nanosleep(struct timespec *t);
extern long do_utimes(char __user * filename, struct timeval * times);
struct itimerval;
extern int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue);
extern int do_getitimer(int which, struct itimerval *value);
extern void getnstimeofday (struct timespec *tv);

static inline void
set_normalized_timespec (struct timespec *ts, time_t sec, long nsec)
{
	while (nsec > NSEC_PER_SEC) {
		nsec -= NSEC_PER_SEC;
		++sec;
	}
	while (unlikely(nsec < 0)) {
		nsec += NSEC_PER_SEC;
		--sec;
	}
	ts->tv_sec = sec;
	ts->tv_nsec = nsec;
}
#define timespec_norm(a) set_normalized_timespec((a), (a)->tv_sec, (a)->tv_nsec)
#endif

#define FD_SETSIZE		__FD_SETSIZE
#define FD_SET(fd,fdsetp)	__FD_SET(fd,fdsetp)
#define FD_CLR(fd,fdsetp)	__FD_CLR(fd,fdsetp)
#define FD_ISSET(fd,fdsetp)	__FD_ISSET(fd,fdsetp)
#define FD_ZERO(fdsetp)		__FD_ZERO(fdsetp)

/*
 * Names of the interval timers, and structure
 * defining a timer setting.
 */
#define	ITIMER_REAL	0
#define	ITIMER_VIRTUAL	1
#define	ITIMER_PROF	2

struct  itimerspec {
        struct  timespec it_interval;    /* timer period */
        struct  timespec it_value;       /* timer expiration */
};

struct	itimerval {
	struct	timeval it_interval;	/* timer interval */
	struct	timeval it_value;	/* current value */
};


/*
 * The IDs of the various system clocks (for POSIX.1b interval timers).
 */
#define CLOCK_REALTIME		  0
#define CLOCK_MONOTONIC	  1
#define CLOCK_PROCESS_CPUTIME_ID 2
#define CLOCK_THREAD_CPUTIME_ID	 3
#define CLOCK_REALTIME_HR	 4
#define CLOCK_MONOTONIC_HR	  5

#define MAX_CLOCKS 6

/*
 * The various flags for setting POSIX.1b interval timers.
 */

#define TIMER_ABSTIME 0x01


#endif