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glibc  2.9
pthread_clock_gettime.c
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00001 /* Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public License as
00006    published by the Free Software Foundation; either version 2.1 of the
00007    License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; see the file COPYING.LIB.  If not,
00016    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
00017    Boston, MA 02111-1307, USA.  */
00018 
00019 #include <errno.h>
00020 #include <stdlib.h>
00021 #include <time.h>
00022 #include <libc-internal.h>
00023 #include "pthreadP.h"
00024 
00025 
00026 #if HP_TIMING_AVAIL
00027 int
00028 __pthread_clock_gettime (clockid_t clock_id, hp_timing_t freq,
00029                       struct timespec *tp)
00030 {
00031   hp_timing_t tsc;
00032 
00033   /* Get the current counter.  */
00034   HP_TIMING_NOW (tsc);
00035 
00036   /* This is the ID of the thread we are looking for.  */
00037   pid_t tid = ((unsigned int) clock_id) >> CLOCK_IDFIELD_SIZE;
00038 
00039   /* Compute the offset since the start time of the process.  */
00040   if (tid == 0 || tid == THREAD_GETMEM (THREAD_SELF, tid))
00041     /* Our own clock.  */
00042     tsc -= THREAD_GETMEM (THREAD_SELF, cpuclock_offset);
00043   else
00044     {
00045       /* This is more complicated.  We have to locate the thread based
00046         on the ID.  This means walking the list of existing
00047         threads.  */
00048       struct pthread *thread = __find_thread_by_id (tid);
00049       if (thread == NULL)
00050        {
00051          __set_errno (EINVAL);
00052          return -1;
00053        }
00054 
00055       /* There is a race here.  The thread might terminate and the stack
00056         become unusable.  But this is the user's problem.  */
00057       tsc -= thread->cpuclock_offset;
00058     }
00059 
00060   /* Compute the seconds.  */
00061   tp->tv_sec = tsc / freq;
00062 
00063   /* And the nanoseconds.  This computation should be stable until
00064      we get machines with about 16GHz frequency.  */
00065   tp->tv_nsec = ((tsc % freq) * 1000000000ull) / freq;
00066 
00067   return 0;
00068 }
00069 #endif