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Annotation of OSKit-Mach/kern/timer.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
        !             4:  * All Rights Reserved.
        !             5:  *
        !             6:  * Permission to use, copy, modify and distribute this software and its
        !             7:  * documentation is hereby granted, provided that both the copyright
        !             8:  * notice and this permission notice appear in all copies of the
        !             9:  * software, derivative works or modified versions, and any portions
        !            10:  * thereof, and that both notices appear in supporting documentation.
        !            11:  *
        !            12:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            13:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            14:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            15:  *
        !            16:  * Carnegie Mellon requests users of this software to return to
        !            17:  *
        !            18:  *  Software Distribution Coordinator  or  [email protected]
        !            19:  *  School of Computer Science
        !            20:  *  Carnegie Mellon University
        !            21:  *  Pittsburgh PA 15213-3890
        !            22:  *
        !            23:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            24:  * the rights to redistribute these changes.
        !            25:  */
        !            26: 
        !            27: #ifndef        _KERN_TIMER_H_
        !            28: #define _KERN_TIMER_H_
        !            29: 
        !            30: #include <cpus.h>
        !            31: #include <stat_time.h>
        !            32: 
        !            33: #include <kern/macro_help.h>
        !            34: 
        !            35: #if    STAT_TIME
        !            36: /*
        !            37:  *     Statistical timer definitions - use microseconds in timer, seconds
        !            38:  *     in high unit field.  No adjustment needed to convert to time_value_t
        !            39:  *     as a result.  Service timers once an hour.
        !            40:  */
        !            41: 
        !            42: #define TIMER_RATE     1000000
        !            43: #define TIMER_HIGH_UNIT        TIMER_RATE
        !            44: #undef TIMER_ADJUST
        !            45: 
        !            46: #else  /* STAT_TIME */
        !            47: /*
        !            48:  *     Machine dependent definitions based on hardware support.
        !            49:  */
        !            50: 
        !            51: #include <machine/timer.h>
        !            52: 
        !            53: #endif /* STAT_TIME */
        !            54: 
        !            55: /*
        !            56:  *     Definitions for accurate timers.  high_bits_check is a copy of
        !            57:  *     high_bits that allows reader to verify that values read are ok.
        !            58:  */
        !            59: 
        !            60: struct timer {
        !            61:        unsigned        low_bits;
        !            62:        unsigned        high_bits;
        !            63:        unsigned        high_bits_check;
        !            64:        unsigned        tstamp;
        !            65: };
        !            66: 
        !            67: typedef struct timer           timer_data_t;
        !            68: typedef        struct timer            *timer_t;
        !            69: 
        !            70: /*
        !            71:  *     Mask to check if low_bits is in danger of overflowing
        !            72:  */
        !            73: 
        !            74: #define        TIMER_LOW_FULL  0x80000000U
        !            75: 
        !            76: /*
        !            77:  *     Kernel timers and current timer array.  [Exported]
        !            78:  */
        !            79: 
        !            80: extern timer_t         current_timer[NCPUS];
        !            81: extern timer_data_t    kernel_timer[NCPUS];
        !            82: 
        !            83: /*
        !            84:  *     save structure for timer readings.  This is used to save timer
        !            85:  *     readings for elapsed time computations.
        !            86:  */
        !            87: 
        !            88: struct timer_save {
        !            89:        unsigned        low;
        !            90:        unsigned        high;
        !            91: };
        !            92: 
        !            93: typedef struct timer_save      timer_save_data_t, *timer_save_t;
        !            94: 
        !            95: /*
        !            96:  *     Exported kernel interface to timers
        !            97:  */
        !            98: 
        !            99: #if    STAT_TIME
        !           100: #define start_timer(timer)
        !           101: #define timer_switch(timer)
        !           102: #else  /* STAT_TIME */
        !           103: extern void    start_timer();
        !           104: extern void    timer_switch();
        !           105: #endif /* STAT_TIME */
        !           106: 
        !           107: extern void            timer_read();
        !           108: extern void            thread_read_times();
        !           109: extern unsigned                timer_delta();
        !           110: 
        !           111: #if    STAT_TIME
        !           112: /*
        !           113:  *     Macro to bump timer values.
        !           114:  */
        !           115: #define timer_bump(timer, usec)                                        \
        !           116: MACRO_BEGIN                                                    \
        !           117:        (timer)->low_bits += usec;                              \
        !           118:        if ((timer)->low_bits & TIMER_LOW_FULL) {               \
        !           119:                timer_normalize(timer);                         \
        !           120:        }                                                       \
        !           121: MACRO_END
        !           122: 
        !           123: #else  /* STAT_TIME */
        !           124: /*
        !           125:  *     Exported hardware interface to timers
        !           126:  */
        !           127: extern void    time_trap_uentry();
        !           128: extern void    time_trap_uexit();
        !           129: extern timer_t time_int_entry();
        !           130: extern void    time_int_exit();
        !           131: #endif /* STAT_TIME */
        !           132: 
        !           133: /*
        !           134:  *     TIMER_DELTA finds the difference between a timer and a saved value,
        !           135:  *     and updates the saved value.  Look at high_bits check field after
        !           136:  *     reading low because that's the first written by a normalize
        !           137:  *     operation; this isn't necessary for current usage because
        !           138:  *     this macro is only used when the timer can't be normalized:
        !           139:  *     thread is not running, or running thread calls it on itself at
        !           140:  *     splsched().
        !           141:  */
        !           142: 
        !           143: #define TIMER_DELTA(timer, save, result)                       \
        !           144: MACRO_BEGIN                                                    \
        !           145:        register unsigned       temp;                           \
        !           146:                                                                \
        !           147:        temp = (timer).low_bits;                                \
        !           148:        if ((save).high != (timer).high_bits_check) {           \
        !           149:                result += timer_delta(&(timer), &(save));       \
        !           150:        }                                                       \
        !           151:        else {                                                  \
        !           152:                result += temp - (save).low;                    \
        !           153:                (save).low = temp;                              \
        !           154:        }                                                       \
        !           155: MACRO_END
        !           156: 
        !           157: #endif /* _KERN_TIMER_H_ */

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