sysdeps/mach/hurd/getitimer.c

   1 /* Copyright (C) 1994-2018 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
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stddef.h>
  19 #include <errno.h>
  20 #include <sys/time.h>
  21 #include <hurd.h>
  22
  23 /* XXX Temporary cheezoid implementation; see __setitmr.c.  */
  24
  25 /* These are defined in __setitmr.c.  */
  26 extern spin_lock_t _hurd_itimer_lock;
  27 extern struct itimerval _hurd_itimerval;
  28 extern struct timeval _hurd_itimer_started;
  29
  30 static inline void
  31 subtract_timeval (struct timeval *from, const struct timeval *subtract)
  32 {
  33   from->tv_usec -= subtract->tv_usec;
  34   from->tv_sec -= subtract->tv_sec;
  35   while (from->tv_usec < 0)
  36     {
  37       --from->tv_sec;
  38       from->tv_usec += 1000000;
  39     }
  40 }
  41
  42 /* Set *VALUE to the current setting of timer WHICH.
  43    Return 0 on success, -1 on errors.  */
  44 int
  45 __getitimer (enum __itimer_which which, struct itimerval *value)
  46 {
  47   struct itimerval val;
  48   struct timeval elapsed;
  49
  50   switch (which)
  51     {
  52     default:
  53       return __hurd_fail (EINVAL);
  54
  55     case ITIMER_VIRTUAL:
  56     case ITIMER_PROF:
  57       return __hurd_fail (ENOSYS);
  58
  59     case ITIMER_REAL:
  60       break;
  61     }
  62
  63   /* Get the time now.  */
  64   if (__gettimeofday (&elapsed, NULL) < 0)
  65     return -1;
  66
  67   /* Extract the current timer setting; and the time it was set, so we can
  68      calculate the time elapsed so far.  */
  69   HURD_CRITICAL_BEGIN;
  70   __spin_lock (&_hurd_itimer_lock);
  71   val = _hurd_itimerval;
  72   subtract_timeval (&elapsed, &_hurd_itimer_started);
  73   __spin_unlock (&_hurd_itimer_lock);
  74   HURD_CRITICAL_END;
  75
  76   if ((val.it_value.tv_sec | val.it_value.tv_usec) != 0)
  77     {
  78       /* There is a pending alarm set.  VAL indicates the interval it was
  79          set for, relative to the time recorded in _hurd_itimer_started.
  80          Now compensate for the time elapsed since to get the user's
  81          conception of the current value of the timer (as if the value
  82          stored decreased every microsecond).  */
  83       if (timercmp (&val.it_value, &elapsed, <))
  84         {
  85           /* Hmm.  The timer should have just gone off, but has not been
  86              reset.  This is a possible timing glitch.  The alarm will signal
  87              soon, so fabricate a value for how soon.  */
  88           val.it_value.tv_sec = 0;
  89           val.it_value.tv_usec = 10; /* Random.  */
  90         }
  91       else
  92         /* Subtract the time elapsed since the timer was set
  93            from the current timer value the user sees.  */
  94         subtract_timeval (&val.it_value, &elapsed);
  95     }
  96
  97   *value = val;
  98   return 0;
  99 }
 100
 101 weak_alias (__getitimer, getitimer)