sysdeps/unix/clock_gettime.c

   1 /* clock_gettime -- Get the current time from a POSIX clockid_t.  Unix version.
   2    Copyright (C) 1999-2004, 2005 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <stdint.h>
  22 #include <time.h>
  23 #include <sys/time.h>
  24 #include <libc-internal.h>
  25 #include <ldsodefs.h>
  26
  27
  28 #if HP_TIMING_AVAIL
  29 /* Clock frequency of the processor.  We make it a 64-bit variable
  30    because some jokers are already playing with processors with more
  31    than 4GHz.  */
  32 static hp_timing_t freq;
  33
  34
  35 /* This function is defined in the thread library.  */
  36 extern int __pthread_clock_gettime (clockid_t clock_id, hp_timing_t freq,
  37                                     struct timespec *tp)
  38      __attribute__ ((__weak__));
  39
  40 static int
  41 hp_timing_gettime (clockid_t clock_id, struct timespec *tp)
  42 {
  43   hp_timing_t tsc;
  44
  45   if (__builtin_expect (freq == 0, 0))
  46     {
  47       /* This can only happen if we haven't initialized the `freq'
  48          variable yet.  Do this now. We don't have to protect this
  49          code against multiple execution since all of them should
  50          lead to the same result.  */
  51       freq = __get_clockfreq ();
  52       if (__builtin_expect (freq == 0, 0))
  53         /* Something went wrong.  */
  54         return -1;
  55     }
  56
  57   if (clock_id != CLOCK_PROCESS_CPUTIME_ID
  58       && __pthread_clock_gettime != NULL)
  59     return __pthread_clock_gettime (clock_id, freq, tp);
  60
  61   /* Get the current counter.  */
  62   HP_TIMING_NOW (tsc);
  63
  64   /* Compute the offset since the start time of the process.  */
  65   tsc -= GL(dl_cpuclock_offset);
  66
  67   /* Compute the seconds.  */
  68   tp->tv_sec = tsc / freq;
  69
  70   /* And the nanoseconds.  This computation should be stable until
  71      we get machines with about 16GHz frequency.  */
  72   tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
  73
  74   return 0;
  75 }
  76 #endif
  77
  78
  79 static inline int
  80 realtime_gettime (struct timespec *tp)
  81 {
  82   struct timeval tv;
  83   int retval = gettimeofday (&tv, NULL);
  84   if (retval == 0)
  85     /* Convert into `timespec'.  */
  86     TIMEVAL_TO_TIMESPEC (&tv, tp);
  87   return retval;
  88 }
  89
  90
  91 /* Get current value of CLOCK and store it in TP.  */
  92 int
  93 clock_gettime (clockid_t clock_id, struct timespec *tp)
  94 {
  95   int retval = -1;
  96   struct timeval tv;
  97
  98   switch (clock_id)
  99     {
 100 #ifdef SYSDEP_GETTIME
 101       SYSDEP_GETTIME;
 102 #endif
 103
 104 #ifndef HANDLED_REALTIME
 105     case CLOCK_REALTIME:
 106       retval = gettimeofday (&tv, NULL);
 107       if (retval == 0)
 108         TIMEVAL_TO_TIMESPEC (&tv, tp);
 109       break;
 110 #endif
 111
 112     default:
 113 #ifdef SYSDEP_GETTIME_CPU
 114       SYSDEP_GETTIME_CPU;
 115 #endif
 116 #if HP_TIMING_AVAIL
 117       if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
 118           == CLOCK_THREAD_CPUTIME_ID)
 119         retval = hp_timing_gettime (clock_id, tp);
 120       else
 121 #endif
 122         __set_errno (EINVAL);
 123       break;
 124
 125 #if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
 126     case CLOCK_PROCESS_CPUTIME_ID:
 127       retval = hp_timing_gettime (clock_id, tp);
 128       break;
 129 #endif
 130     }
 131
 132   return retval;
 133 }