sysdeps/unix/clock_gettime.c

   1 /* clock_gettime -- Get the current time from a POSIX clockid_t.  Unix version.
   2    Copyright (C) 1999-2016 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, see
  17    <http://www.gnu.org/licenses/>.  */
  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
  39 static int
  40 hp_timing_gettime (clockid_t clock_id, struct timespec *tp)
  41 {
  42   hp_timing_t tsc;
  43
  44   if (__glibc_unlikely (freq == 0))
  45     {
  46       /* This can only happen if we haven't initialized the `freq'
  47          variable yet.  Do this now. We don't have to protect this
  48          code against multiple execution since all of them should
  49          lead to the same result.  */
  50       freq = __get_clockfreq ();
  51       if (__glibc_unlikely (freq == 0))
  52         /* Something went wrong.  */
  53         return -1;
  54     }
  55
  56   if (clock_id != CLOCK_PROCESS_CPUTIME_ID
  57       && __pthread_clock_gettime != NULL)
  58     return __pthread_clock_gettime (clock_id, freq, tp);
  59
  60   /* Get the current counter.  */
  61   HP_TIMING_NOW (tsc);
  62
  63   /* Compute the offset since the start time of the process.  */
  64   tsc -= GL(dl_cpuclock_offset);
  65
  66   /* Compute the seconds.  */
  67   tp->tv_sec = tsc / freq;
  68
  69   /* And the nanoseconds.  This computation should be stable until
  70      we get machines with about 16GHz frequency.  */
  71   tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
  72
  73   return 0;
  74 }
  75 #endif
  76
  77
  78 static inline int
  79 realtime_gettime (struct timespec *tp)
  80 {
  81   struct timeval tv;
  82   int retval = gettimeofday (&tv, NULL);
  83   if (retval == 0)
  84     /* Convert into `timespec'.  */
  85     TIMEVAL_TO_TIMESPEC (&tv, tp);
  86   return retval;
  87 }
  88
  89
  90 /* Get current value of CLOCK and store it in TP.  */
  91 int
  92 __clock_gettime (clockid_t clock_id, struct timespec *tp)
  93 {
  94   int retval = -1;
  95
  96   switch (clock_id)
  97     {
  98 #ifdef SYSDEP_GETTIME
  99       SYSDEP_GETTIME;
 100 #endif
 101
 102 #ifndef HANDLED_REALTIME
 103     case CLOCK_REALTIME:
 104       {
 105         struct timeval tv;
 106         retval = gettimeofday (&tv, NULL);
 107         if (retval == 0)
 108           TIMEVAL_TO_TIMESPEC (&tv, tp);
 109       }
 110       break;
 111 #endif
 112
 113     default:
 114 #ifdef SYSDEP_GETTIME_CPU
 115       SYSDEP_GETTIME_CPU (clock_id, tp);
 116 #endif
 117 #if HP_TIMING_AVAIL
 118       if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
 119           == CLOCK_THREAD_CPUTIME_ID)
 120         retval = hp_timing_gettime (clock_id, tp);
 121       else
 122 #endif
 123         __set_errno (EINVAL);
 124       break;
 125
 126 #if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
 127     case CLOCK_PROCESS_CPUTIME_ID:
 128       retval = hp_timing_gettime (clock_id, tp);
 129       break;
 130 #endif
 131     }
 132
 133   return retval;
 134 }
 135 weak_alias (__clock_gettime, clock_gettime)
 136 libc_hidden_def (__clock_gettime)