sysdeps/unix/clock_gettime.c

   1 /* Copyright (C) 1999, 2000, 2001, 2002 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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 <ldsodefs.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 /* This function is defined in the thread library.  */
  35 extern int __pthread_clock_gettime (hp_timing_t freq, struct timespec *tp)
  36      __attribute__ ((__weak__));
  37 #endif
  38
  39
  40 /* Get current value of CLOCK and store it in TP.  */
  41 int
  42 clock_gettime (clockid_t clock_id, struct timespec *tp)
  43 {
  44   struct timeval tv;
  45   int retval = -1;
  46
  47   switch (clock_id)
  48     {
  49     case CLOCK_REALTIME:
  50       retval = gettimeofday (&tv, NULL);
  51       if (retval == 0)
  52         /* Convert into `timespec'.  */
  53         TIMEVAL_TO_TIMESPEC (&tv, tp);
  54       break;
  55
  56 #if HP_TIMING_AVAIL
  57     case CLOCK_PROCESS_CPUTIME_ID:
  58     case CLOCK_THREAD_CPUTIME_ID:
  59       {
  60         hp_timing_t tsc;
  61
  62         if (__builtin_expect (freq == 0, 0))
  63           {
  64             /* This can only happen if we haven't initialized the `freq'
  65                variable yet.  Do this now. We don't have to protect this
  66                code against multiple execution since all of them should
  67                lead to the same result.  */
  68             freq = __get_clockfreq ();
  69             if (__builtin_expect (freq == 0, 0))
  70               /* Something went wrong.  */
  71               break;
  72           }
  73
  74         if (clock_id == CLOCK_THREAD_CPUTIME_ID
  75             && __pthread_clock_gettime != NULL)
  76           {
  77             retval = __pthread_clock_gettime (freq, tp);
  78             break;
  79           }
  80
  81         /* Get the current counter.  */
  82         HP_TIMING_NOW (tsc);
  83
  84         /* Compute the offset since the start time of the process.  */
  85         tsc -= GL(dl_cpuclock_offset);
  86
  87         /* Compute the seconds.  */
  88         tp->tv_sec = tsc / freq;
  89
  90         /* And the nanoseconds.  This computation should be stable until
  91            we get machines with about 16GHz frequency.  */
  92         tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
  93
  94         retval = 0;
  95       }
  96     break;
  97 #endif
  98
  99     default:
 100       __set_errno (EINVAL);
 101       break;
 102     }
 103
 104   return retval;
 105 }