librt/clock_gettime.c

   1 /* clock_gettime -- Get current time from a POSIX clockid_t.  Linux version.
   2    Copyright (C) 2003, 2004 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 <sysdep.h>
  20 #include <errno.h>
  21 #include <time.h>
  22 #include "kernel-posix-cpu-timers.h"
  23 #include <bits/kernel-features.h>
  24
  25
  26 #define SYSCALL_GETTIME \
  27   retval = INLINE_SYSCALL (clock_gettime, 2, clock_id, tp); \
  28   break
  29
  30 #ifdef __ASSUME_POSIX_TIMERS
  31
  32 /* This means the REALTIME and MONOTONIC clock are definitely
  33    supported in the kernel.  */
  34 # define SYSDEP_GETTIME                                                       \
  35   SYSDEP_GETTIME_CPUTIME                                                      \
  36   case CLOCK_REALTIME:                                                        \
  37   case CLOCK_MONOTONIC:                                                       \
  38     SYSCALL_GETTIME
  39
  40 # define __libc_missing_posix_timers 0
  41 #elif defined __NR_clock_gettime
  42 /* Is the syscall known to exist?  */
  43 int __libc_missing_posix_timers attribute_hidden;
  44
  45 static inline int
  46 maybe_syscall_gettime (clockid_t clock_id, struct timespec *tp)
  47 {
  48   int e = EINVAL;
  49
  50   if (!__libc_missing_posix_timers)
  51     {
  52       INTERNAL_SYSCALL_DECL (err);
  53       int r = INTERNAL_SYSCALL (clock_gettime, err, 2, clock_id, tp);
  54       if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  55         return 0;
  56
  57       e = INTERNAL_SYSCALL_ERRNO (r, err);
  58       if (e == ENOSYS)
  59         {
  60           __libc_missing_posix_timers = 1;
  61           e = EINVAL;
  62         }
  63     }
  64
  65   return e;
  66 }
  67
  68 /* The REALTIME and MONOTONIC clock might be available.  Try the
  69    syscall first.  */
  70 # define SYSDEP_GETTIME                                                       \
  71   SYSDEP_GETTIME_CPUTIME                                                      \
  72   case CLOCK_REALTIME:                                                        \
  73   case CLOCK_MONOTONIC:                                                       \
  74     retval = maybe_syscall_gettime (clock_id, tp);                            \
  75     if (retval == 0)                                                          \
  76       break;                                                                  \
  77     /* Fallback code.  */                                                     \
  78     if (retval == EINVAL && clock_id == CLOCK_REALTIME)                       \
  79       retval = realtime_gettime (tp);                                         \
  80     else                                                                      \
  81       {                                                                       \
  82         __set_errno (retval);                                                 \
  83         retval = -1;                                                          \
  84       }                                                                       \
  85     break;
  86 #endif
  87
  88 #ifdef __NR_clock_gettime
  89 /* We handled the REALTIME clock here.  */
  90 # define HANDLED_REALTIME       1
  91 # define HANDLED_CPUTIME        1
  92
  93 # if __ASSUME_POSIX_CPU_TIMERS > 0
  94
  95 #  define SYSDEP_GETTIME_CPU SYSCALL_GETTIME
  96 #  define SYSDEP_GETTIME_CPUTIME        /* Default catches them too.  */
  97
  98 # else
  99
 100 int __libc_missing_posix_cpu_timers attribute_hidden;
 101
 102 static int
 103 maybe_syscall_gettime_cpu (clockid_t clock_id, struct timespec *tp)
 104 {
 105   int e = EINVAL;
 106
 107   if (!__libc_missing_posix_cpu_timers)
 108     {
 109       INTERNAL_SYSCALL_DECL (err);
 110       int r = INTERNAL_SYSCALL (clock_gettime, err, 2, clock_id, tp);
 111       if (!INTERNAL_SYSCALL_ERROR_P (r, err))
 112         return 0;
 113
 114       e = INTERNAL_SYSCALL_ERRNO (r, err);
 115 # ifndef __ASSUME_POSIX_TIMERS
 116       if (e == ENOSYS)
 117         {
 118           __libc_missing_posix_timers = 1;
 119           __libc_missing_posix_cpu_timers = 1;
 120           e = EINVAL;
 121         }
 122       else
 123 # endif
 124         {
 125           if (e == EINVAL)
 126             {
 127               /* Check whether the kernel supports CPU clocks at all.
 128                  If not, record it for the future.  */
 129               r = INTERNAL_SYSCALL (clock_getres, err, 2,
 130                                     MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED),
 131                                     NULL);
 132               if (INTERNAL_SYSCALL_ERROR_P (r, err))
 133                 __libc_missing_posix_cpu_timers = 1;
 134             }
 135         }
 136     }
 137
 138   return e;
 139 }
 140
 141 #  define SYSDEP_GETTIME_CPU                                                  \
 142   retval = maybe_syscall_gettime_cpu (clock_id, tp);                          \
 143   if (retval == 0)                                                            \
 144     break;                                                                    \
 145   if (retval != EINVAL || !__libc_missing_posix_cpu_timers)                   \
 146     {                                                                         \
 147       __set_errno (retval);                                                   \
 148       retval = -1;                                                            \
 149       break;                                                                  \
 150     }                                                                         \
 151   retval = -1 /* Otherwise continue on to the HP_TIMING version.  */;
 152
 153 static inline int
 154 maybe_syscall_gettime_cputime (clockid_t clock_id, struct timespec *tp)
 155 {
 156   return maybe_syscall_gettime_cpu
 157     (clock_id == CLOCK_THREAD_CPUTIME_ID
 158      ? MAKE_THREAD_CPUCLOCK (0, CPUCLOCK_SCHED)
 159      : MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED),
 160      tp);
 161 }
 162
 163 #  define SYSDEP_GETTIME_CPUTIME                                              \
 164     case CLOCK_PROCESS_CPUTIME_ID:                                            \
 165     case CLOCK_THREAD_CPUTIME_ID:                                             \
 166       retval = maybe_syscall_gettime_cputime (clock_id, tp);                  \
 167       if (retval == 0)                                                        \
 168         break;                                                                \
 169       if (retval != EINVAL || !__libc_missing_posix_cpu_timers)               \
 170         {                                                                     \
 171           __set_errno (retval);                                               \
 172           retval = -1;                                                        \
 173           break;                                                              \
 174         }                                                                     \
 175       retval = hp_timing_gettime (clock_id, tp);                              \
 176       break;
 177 #  if !HP_TIMING_AVAIL
 178 #   define hp_timing_gettime(clock_id, tp) (__set_errno (EINVAL), -1)
 179 #  endif
 180
 181 # endif
 182 #endif
 183
 184 #include <errno.h>
 185 #include <stdint.h>
 186 #include <time.h>
 187 #include <sys/time.h>
 188 #include <ldsodefs.h>
 189
 190
 191 #if HP_TIMING_AVAIL
 192 /* Clock frequency of the processor.  We make it a 64-bit variable
 193    because some jokers are already playing with processors with more
 194    than 4GHz.  */
 195 static hp_timing_t freq;
 196
 197
 198 /* This function is defined in the thread library.  */
 199 extern int __pthread_clock_gettime (clockid_t clock_id, hp_timing_t freq,
 200                                     struct timespec *tp)
 201      __attribute__ ((__weak__));
 202
 203 static int
 204 hp_timing_gettime (clockid_t clock_id, struct timespec *tp)
 205 {
 206   hp_timing_t tsc;
 207
 208   if (__builtin_expect (freq == 0, 0))
 209     {
 210       /* This can only happen if we haven't initialized the `freq'
 211          variable yet.  Do this now. We don't have to protect this
 212          code against multiple execution since all of them should
 213          lead to the same result.  */
 214       freq = __get_clockfreq ();
 215       if (__builtin_expect (freq == 0, 0))
 216         /* Something went wrong.  */
 217         return -1;
 218     }
 219
 220   if (clock_id != CLOCK_PROCESS_CPUTIME_ID
 221       && __pthread_clock_gettime != NULL)
 222     return __pthread_clock_gettime (clock_id, freq, tp);
 223
 224   /* Get the current counter.  */
 225   HP_TIMING_NOW (tsc);
 226
 227   /* Compute the offset since the start time of the process.  */
 228   tsc -= GL(dl_cpuclock_offset);
 229
 230   /* Compute the seconds.  */
 231   tp->tv_sec = tsc / freq;
 232
 233   /* And the nanoseconds.  This computation should be stable until
 234      we get machines with about 16GHz frequency.  */
 235   tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;
 236
 237   return 0;
 238 }
 239 #endif
 240
 241
 242 static inline int
 243 realtime_gettime (struct timespec *tp)
 244 {
 245   struct timeval tv;
 246   int retval = gettimeofday (&tv, NULL);
 247   if (retval == 0)
 248     /* Convert into `timespec'.  */
 249     TIMEVAL_TO_TIMESPEC (&tv, tp);
 250   return retval;
 251 }
 252
 253 librt_hidden_proto (clock_gettime)
 254 /* Get current value of CLOCK and store it in TP.  */
 255 int
 256 clock_gettime (clockid_t clock_id, struct timespec *tp)
 257 {
 258   int retval = -1;
 259 #ifndef HANDLED_REALTIME
 260   struct timeval tv;
 261 #endif
 262
 263   switch (clock_id)
 264     {
 265 #ifdef SYSDEP_GETTIME
 266       SYSDEP_GETTIME;
 267 #endif
 268
 269 #ifndef HANDLED_REALTIME
 270     case CLOCK_REALTIME:
 271       retval = gettimeofday (&tv, NULL);
 272       if (retval == 0)
 273         TIMEVAL_TO_TIMESPEC (&tv, tp);
 274       break;
 275 #endif
 276
 277     default:
 278 #ifdef SYSDEP_GETTIME_CPU
 279       SYSDEP_GETTIME_CPU;
 280 #endif
 281 #if HP_TIMING_AVAIL
 282       if ((clock_id & ((1 << CLOCK_IDFIELD_SIZE) - 1))
 283           == CLOCK_THREAD_CPUTIME_ID)
 284         retval = hp_timing_gettime (clock_id, tp);
 285       else
 286 #endif
 287         __set_errno (EINVAL);
 288       break;
 289
 290 #if HP_TIMING_AVAIL && !defined HANDLED_CPUTIME
 291     case CLOCK_PROCESS_CPUTIME_ID:
 292       retval = hp_timing_gettime (clock_id, tp);
 293       break;
 294 #endif
 295     }
 296
 297   return retval;
 298 }
 299 librt_hidden_def (clock_gettime)