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

     /* 
      * Mach Operating System
      * Copyright (c) 1991,1990,1989,1988,1987 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 2.5  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 <kern/macro_help.h>
    
    #if     STAT_TIME
    /*
     *      Statistical timer definitions - use microseconds in timer, seconds
     *      in high unit field.  No adjustment needed to convert to time_value_t
     *      as a result.  Service timers once an hour.
     */
    
    #define TIMER_RATE      1000000
    #define TIMER_HIGH_UNIT TIMER_RATE
    #undef  TIMER_ADJUST
    
    #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        low_bits;
           unsigned        high_bits;
           unsigned        high_bits_check;
           unsigned        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
   
   /*
    *      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        low;
           unsigned        high;
   };
   
   typedef struct timer_save       timer_save_data_t, *timer_save_t;
   
   /*
    *      Exported kernel interface to timers
    */
   
   #if     STAT_TIME
   #define start_timer(timer)
   #define timer_switch(timer)
   #else   STAT_TIME
   extern void     start_timer();
   extern void     timer_switch();
   #endif  STAT_TIME
   
   extern void             timer_read();
   extern void             thread_read_times();
   extern unsigned         timer_delta();
   
   #if     STAT_TIME
   /*
    *      Macro to bump timer values.
    */     
   #define timer_bump(timer, usec)                                 \
   MACRO_BEGIN                                                     \
           (timer)->low_bits += usec;                              \
           if ((timer)->low_bits & TIMER_LOW_FULL) {               \
                   timer_normalize(timer);                         \
           }                                                       \
   MACRO_END
   
   #else   STAT_TIME
   /*
    *      Exported hardware interface to timers
    */
   extern void     time_trap_uentry();
   extern void     time_trap_uexit();
   extern timer_t  time_int_entry();
   extern void     time_int_exit();
   #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       temp;                           \
                                                                   \
           temp = (timer).low_bits;                                \
           if ((save).high != (timer).high_bits_check) {           \
                   result += timer_delta(&(timer), &(save));       \
           }                                                       \
           else {                                                  \
                   result += temp - (save).low;                    \
                   (save).low = temp;                              \
           }                                                       \
   MACRO_END
   
   #endif  _KERN_TIMER_H_

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