nptl/pthread_clock_gettime.c

   1 /* Copyright (C) 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 License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    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; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <errno.h>
  20 #include <stdlib.h>
  21 #include <time.h>
  22 #include <libc-internal.h>
  23 #include "pthreadP.h"
  24
  25
  26 #if HP_TIMING_AVAIL
  27 int
  28 __pthread_clock_gettime (clockid_t clock_id, hp_timing_t freq,
  29                          struct timespec *tp)
  30 {
  31   hp_timing_t tsc;
  32
  33   /* Get the current counter.  */
  34   HP_TIMING_NOW (tsc);
  35
  36   /* This is the ID of the thread we are looking for.  */
  37   pid_t tid = ((unsigned int) clock_id) >> CLOCK_IDFIELD_SIZE;
  38
  39   /* Compute the offset since the start time of the process.  */
  40   if (tid == 0 || tid == THREAD_GETMEM (THREAD_SELF, tid))
  41     /* Our own clock.  */
  42     tsc -= THREAD_GETMEM (THREAD_SELF, cpuclock_offset);
  43   else
  44     {
  45       /* This is more complicated.  We have to locate the thread based
  46          on the ID.  This means walking the list of existing
  47          threads.  */
  48       struct pthread *thread = __find_thread_by_id (tid);
  49       if (thread == NULL)
  50         {
  51           __set_errno (EINVAL);
  52           return -1;
  53         }
  54
  55       /* There is a race here.  The thread might terminate and the stack
  56          become unusable.  But this is the user's problem.  */
  57       tsc -= thread->cpuclock_offset;
  58     }
  59
  60   /* Compute the seconds.  */
  61   tp->tv_sec = tsc / freq;
  62
  63   /* And the nanoseconds.  This computation should be stable until
  64      we get machines with about 16GHz frequency.  */
  65   tp->tv_nsec = ((tsc % freq) * 1000000000ull) / freq;
  66
  67   return 0;
  68 }
  69 #endif