sysdeps/unix/sysv/linux/prof-freq.c

   1 /* Determine realtime clock frequency.
   2    Copyright (C) 2003, 2004, 2006 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 <sys/time.h>
  21 #include <libc-internal.h>
  22 #include <kernel-features.h>
  23 #include <ldsodefs.h>
  24
  25
  26 int
  27 __profile_frequency (void)
  28 {
  29 #ifdef __ASSUME_AT_CLKTCK
  30   return GLRO(dl_clktck);
  31 #else
  32   if (GLRO(dl_clktck) != 0)
  33     return GLRO(dl_clktck);
  34
  35   struct itimerval tim;
  36
  37   tim.it_interval.tv_sec = 0;
  38   tim.it_interval.tv_usec = 1;
  39   tim.it_value.tv_sec = 0;
  40   tim.it_value.tv_usec = 0;
  41
  42   __setitimer (ITIMER_REAL, &tim, 0);
  43   __setitimer (ITIMER_REAL, 0, &tim);
  44
  45   if (tim.it_interval.tv_usec < 2)
  46     return 0;
  47
  48   return 1000000 / tim.it_interval.tv_usec;
  49 #endif
  50 }
  51 libc_hidden_def (__profile_frequency)