sysdeps/unix/clock_gettime.c

   1 /* Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <errno.h>
  20 #include <stdint.h>
  21 #include <time.h>
  22 #include <sys/time.h>
  23 #include <libc-internal.h>
  24 #include <hp-timing.h>
  25
  26
  27 #if HP_TIMING_AVAIL
  28 /* Clock frequency of the processor.  We make it a 64-bit variable
  29    because some jokers are already playing with processors with more
  30    than 4GHz.  */
  31 static hp_timing_t freq;
  32
  33
  34 /* We need the starting time for the process.  */
  35 extern hp_timing_t _dl_cpuclock_offset;
  36
  37
  38 /* This function is defined in the thread library.  */
  39 extern int __pthread_clock_gettime (hp_timing_t freq, struct timespec *tp)
  40      __attribute__ ((__weak__));
  41 #endif
  42
  43
  44 /* Get current value of CLOCK and store it in TP.  */
  45 int
  46 clock_gettime (clockid_t clock_id, struct timespec *tp)
  47 {
  48   struct timeval tv;
  49   int retval = -1;
  50
  51   switch (clock_id)
  52     {
  53     case CLOCK_REALTIME:
  54       retval = gettimeofday (&tv, NULL);
  55       if (retval == 0)
  56         /* Convert into `timespec'.  */
  57         TIMEVAL_TO_TIMESPEC (&tv, tp);
  58       break;
  59
  60 #if HP_TIMING_AVAIL
  61     case CLOCK_PROCESS_CPUTIME_ID:
  62     case CLOCK_THREAD_CPUTIME_ID:
  63       {
  64         hp_timing_t tsc;
  65
  66         if (__builtin_expect (freq == 0, 0))
  67           {
  68             /* This can only happen if we haven't initialized the `freq'
  69                variable yet.  Do this now. We don't have to protect this
  70                code against multiple execution since all of them should
  71                lead to the same result.  */
  72             freq = __get_clockfreq ();
  73             if (__builtin_expect (freq == 0, 0))
  74               /* Something went wrong.  */
  75               break;
  76           }
  77
  78         if (clock_id == CLOCK_THREAD_CPUTIME_ID
  79             && __pthread_clock_gettime != NULL)
  80           {
  81             retval = __pthread_clock_gettime (freq, tp);
  82             break;
  83           }
  84
  85         /* Get the current counter.  */
  86         HP_TIMING_NOW (tsc);
  87
  88         /* Compute the offset since the start time of the process.  */
  89         tsc -= _dl_cpuclock_offset;
  90
  91         /* Compute the seconds.  */
  92         tp->tv_sec = tsc / freq;
  93
  94         /* And the nanoseconds.  This computation should be stable until
  95            we get machines with about 16GHz frequency.  */
  96         tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
  97
  98         retval = 0;
  99       }
 100     break;
 101 #endif
 102
 103     default:
 104       __set_errno (EINVAL);
 105       break;
 106     }
 107
 108   return retval;
 109 }