FreeBSD/Linux Kernel Cross Reference
sys/kern/timer.h

     /* 
      * Mach Operating System
      * Copyright (c) 1993-1987 Carnegie Mellon University
      * All Rights Reserved.
      * 
      * Permission to use, copy, modify and distribute this software and its
      * documentation is hereby granted, provided that both the copyright
      * notice and this permission notice appear in all copies of the
      * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     * 
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
     * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     * 
     * Carnegie Mellon requests users of this software to return to
     * 
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     * 
     * any improvements or extensions that they make and grant Carnegie Mellon
     * the rights to redistribute these changes.
     */
    /*
     * HISTORY
     * $Log:        timer.h,v $
     * Revision 2.6  93/11/17  17:33:00  dbg
     *      If no machine-dependent timer is used: maintain timer in seconds
     *      and nanoseconds, and use microseconds (or the nearest binary
     *      approximation thereof) for the scheduling units.
     *      [93/01/25            dbg]
     * 
     * Revision 2.5  92/05/21  17:17:07  jfriedl
     *      Appended 'U' to constants that would otherwise be signed.
     *      [92/05/16            jfriedl]
     * 
     * Revision 2.4  91/05/14  16:50:00  mrt
     *      Correcting copyright
     * 
     * Revision 2.3  91/02/05  17:31:10  mrt
     *      Changed to new Mach copyright
     *      [91/02/01  16:21:08  mrt]
     * 
     * Revision 2.2  90/08/07  18:00:13  rpd
     *      Picked up new timer representation.
     * 
     * Revision 2.1  89/08/03  15:57:34  rwd
     * Created.
     * 
     * 27-Oct-88  David Black (dlb) at Carnegie-Mellon University
     *      Added TIMER_LOW_FULL mask to check for possible overflow of
     *      low_bits field.  Removed TIMER_SERVICE flag.
     *
     * Revision 2.3  88/08/24  02:49:17  mwyoung
     *      Adjusted include file references.
     *      [88/08/17  02:25:43  mwyoung]
     * 
     *
     *  7-Apr-88  David Black (dlb) at Carnegie-Mellon University
     *      Added interface definitions and null routines for STAT_TIME.
     *
     * 19-Feb-88  David Black (dlb) at Carnegie-Mellon University
     *      Renamed fields, added timer_save structure.
     *
     * 31-May-87  Avadis Tevanian (avie) at Carnegie-Mellon University
     *      machine/machtimer.h -> machine/timer.h
     *
     * 23-Feb-87  David L. Black (dlb) at Carnegie-Mellon University
     *      Created.
     */ 
    
    #ifndef _KERN_TIMER_H_
    #define _KERN_TIMER_H_
    
    #include <cpus.h>
    #include <stat_time.h>
    
    #include <mach/time_spec.h>
    #include <kern/macro_help.h>
    
    #if     STAT_TIME
    /*
     *      Statistical timer definitions - use nanoseconds in timer, seconds
     *      in high unit field.  Use microseconds as scheduling unit: or,
     *      since we use a shift, 10**9/1024.
     */
    
    /*
     *      Timers themselves are counted in seconds and nanoseconds.
     */
    #define TIMER_HIGH_UNIT NANOSEC_PER_SEC
    
    /*
     *      USAGE_RATE is the unit for cpu_usage and sched_usage.
     *      It is nanoseconds >> 10 (10**9 / 1024).
     */
    #define USAGE_RATE      (TIMER_HIGH_UNIT >> 10)
                                   /* (10**9)/(2**10) == 976562.5 */
   
   #define TIMER_LOW_TO_USAGE(nanos)       ((nanos) >> 10)
   #define TIMER_HIGH_TO_USAGE(secs)       ((secs) * USAGE_RATE)
   
           /* (((secs)*TIMER_HIGH_UNIT)>>10), but this will overflow */
   
   #undef  TIMER_TO_TIMESPEC               /* timers == time_specs */
   
   #else   /* STAT_TIME */
   /*
    *      Machine dependent definitions based on hardware support.
    */
   
   #include <machine/timer.h>
   
   #endif  /* STAT_TIME */
   
   /*
    *      Definitions for accurate timers.  high_bits_check is a copy of
    *      high_bits that allows reader to verify that values read are ok.
    */
   
   struct timer {
           unsigned int    low_bits;
           unsigned int    high_bits;
           unsigned int    high_bits_check;
           unsigned int    tstamp;
   };
   
   typedef struct timer            timer_data_t;
   typedef struct timer            *timer_t;
   
   /*
    *      Mask to check if low_bits is in danger of overflowing
    */
   
   #define TIMER_LOW_FULL  0x80000000U             /* assumes 32 bits! */
   
   /*
    *      Kernel timers and current timer array.  [Exported]
    */
   
   extern timer_t          current_timer[NCPUS];
   extern timer_data_t     kernel_timer[NCPUS];
   
   /*
    *      save structure for timer readings.  This is used to save timer
    *      readings for elapsed time computations.
    */
   
   struct timer_save {
           unsigned int    low;
           unsigned int    high;
   };
   
   typedef struct timer_save       timer_save_data_t, *timer_save_t;
   
   /*
    *      Exported kernel interface to timers
    */
   
   extern void     init_timers(void);
   
   #if     STAT_TIME
   #define start_timer(timer)
   #define timer_switch(timer)
   #else   /* STAT_TIME */
   extern void     start_timer(timer_t timer);
   extern void     timer_switch(timer_t new_timer);
   #endif  /* STAT_TIME */
   
   extern void             timer_init(
                   timer_t         timer);
   
   extern void             timer_read(
                   timer_t         timer,
                   time_spec_t     *tv);
   
   extern void             thread_read_times(
                   thread_t        thread,
                   time_spec_t     *user_time_p,
                   time_spec_t     *system_time_p);
   
   extern unsigned int     timer_delta(
                   timer_t         timer,
                   timer_save_t    save);
   
   #if     STAT_TIME
   /*
    *      Macro to bump timer values.
    */     
   #define timer_bump(timer, nsec)                                 \
   MACRO_BEGIN                                                     \
           (timer)->low_bits += nsec;                              \
           if ((timer)->low_bits & TIMER_LOW_FULL) {               \
                   timer_normalize(timer);                         \
           }                                                       \
   MACRO_END
   
   extern void
   timer_normalize(timer_t);
   
   #else   /* STAT_TIME */
   /*
    *      Exported hardware interface to timers
    */
   extern void     time_trap_uentry(unsigned int timestamp);
   extern void     time_trap_uexit(unsigned int timestamp);
   extern timer_t  time_int_entry(unsigned int timestamp, timer_t new_timer);
   extern void     time_int_exit(unsigned int timestamp, timer_t old_timer);
   #endif  /* STAT_TIME */
   
   /*
    *      TIMER_DELTA finds the difference between a timer and a saved value,
    *      and updates the saved value.  Look at high_bits check field after
    *      reading low because that's the first written by a normalize
    *      operation; this isn't necessary for current usage because
    *      this macro is only used when the timer can't be normalized:
    *      thread is not running, or running thread calls it on itself at
    *      splsched().
    */
   
   #define TIMER_DELTA(timer, save, result)                        \
   MACRO_BEGIN                                                     \
           register unsigned int   temp;                           \
                                                                   \
           temp = (timer).low_bits;                                \
           if ((save).high != (timer).high_bits_check) {           \
               result += timer_delta(&(timer), &(save));           \
           }                                                       \
           else {                                                  \
               result += TIMER_LOW_TO_USAGE(temp - (save).low);    \
               (save).low = temp;                                  \
           }                                                       \
   MACRO_END
   
   #endif  /* _KERN_TIMER_H_ */

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