nptl/pthread_condattr_setclock.c

   1 /* Copyright (C) 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
   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 <assert.h>
  20 #include <errno.h>
  21 #include <stdbool.h>
  22 #include <time.h>
  23 #include <sysdep.h>
  24 #include "pthreadP.h"
  25 #include <kernel-features.h>
  26
  27
  28 int
  29 pthread_condattr_setclock (attr, clock_id)
  30      pthread_condattr_t *attr;
  31      clockid_t clock_id;
  32 {
  33   /* Only a few clocks are allowed.  CLOCK_REALTIME is always allowed.
  34      CLOCK_MONOTONIC only if the kernel has the necessary support.  */
  35   if (clock_id == CLOCK_MONOTONIC)
  36     {
  37 #ifndef __ASSUME_POSIX_TIMERS
  38 # ifdef __NR_clock_getres
  39       /* Check whether the clock is available.  */
  40       static int avail;
  41
  42       if (avail == 0)
  43         {
  44           struct timespec ts;
  45
  46           INTERNAL_SYSCALL_DECL (err);
  47           int val;
  48           val = INTERNAL_SYSCALL (clock_getres, err, 2, CLOCK_MONOTONIC, &ts);
  49           avail = INTERNAL_SYSCALL_ERROR_P (val, err) ? -1 : 1;
  50         }
  51
  52       if (avail < 0)
  53 # endif
  54         /* Not available.  */
  55         return EINVAL;
  56 #endif
  57     }
  58   else if (clock_id != CLOCK_REALTIME)
  59     /* If more clocks are allowed some day the storing of the clock ID
  60        in the pthread_cond_t structure needs to be adjusted.  */
  61     return EINVAL;
  62
  63   /* Make sure the value fits in the bits we reserved.  */
  64   assert (clock_id < (1 << COND_NWAITERS_SHIFT));
  65
  66   int *valuep = &((struct pthread_condattr *) attr)->value;
  67
  68   *valuep = ((*valuep & ~(((1 << COND_NWAITERS_SHIFT) - 1) << 1))
  69              | (clock_id << 1));
  70
  71   return 0;
  72 }