sysdeps/unix/clock_gettime.c

   1 /* Copyright (C) 1999, 2000, 2001, 2002, 2003 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 (clockid_t clock_id, hp_timing_t freq,
  36                                     struct timespec *tp)
  37      __attribute__ ((__weak__));
  38 #endif
  39
  40
  41 /* Get current value of CLOCK and store it in TP.  */
  42 int
  43 clock_gettime (clockid_t clock_id, struct timespec *tp)
  44 {
  45   int retval = -1;
  46
  47   switch (clock_id)
  48     {
  49 #define HANDLE_REALTIME \
  50       do {                                                                    \
  51         struct timeval tv;                                                    \
  52         retval = gettimeofday (&tv, NULL);                                    \
  53         if (retval == 0)                                                      \
  54           /* Convert into `timespec'.  */                                     \
  55           TIMEVAL_TO_TIMESPEC (&tv, tp);                                      \
  56       } while (0)
  57
  58 #ifdef SYSDEP_GETTIME
  59       SYSDEP_GETTIME;
  60 #endif
  61
  62 #ifndef HANDLED_REALTIME
  63     case CLOCK_REALTIME:
  64       HANDLE_REALTIME;
  65       break;
  66 #endif
  67
  68     default:
  69 #if HP_TIMING_AVAIL
  70       if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
  71           != CLOCK_THREAD_CPUTIME_ID)
  72 #endif
  73         {
  74           __set_errno (EINVAL);
  75           break;
  76         }
  77
  78 #if HP_TIMING_AVAIL
  79       /* FALLTHROUGH.  */
  80     case CLOCK_PROCESS_CPUTIME_ID:
  81       {
  82         hp_timing_t tsc;
  83
  84         if (__builtin_expect (freq == 0, 0))
  85           {
  86             /* This can only happen if we haven't initialized the `freq'
  87                variable yet.  Do this now. We don't have to protect this
  88                code against multiple execution since all of them should
  89                lead to the same result.  */
  90             freq = __get_clockfreq ();
  91             if (__builtin_expect (freq == 0, 0))
  92               /* Something went wrong.  */
  93               break;
  94           }
  95
  96         if (clock_id != CLOCK_PROCESS_CPUTIME_ID
  97             && __pthread_clock_gettime != NULL)
  98           {
  99             retval = __pthread_clock_gettime (clock_id, freq, tp);
 100             break;
 101           }
 102
 103         /* Get the current counter.  */
 104         HP_TIMING_NOW (tsc);
 105
 106         /* Compute the offset since the start time of the process.  */
 107         tsc -= GL(dl_cpuclock_offset);
 108
 109         /* Compute the seconds.  */
 110         tp->tv_sec = tsc / freq;
 111
 112         /* And the nanoseconds.  This computation should be stable until
 113            we get machines with about 16GHz frequency.  */
 114         tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
 115
 116         retval = 0;
 117       }
 118     break;
 119 #endif
 120     }
 121
 122   return retval;
 123 }