sysdeps/mach/hurd/getitimer.c

   1 /* Copyright (C) 1994-2023 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    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <stddef.h>
  19 #include <errno.h>
  20 #include <sys/time.h>
  21 #include <hurd.h>
  22 #include <mach.h>
  23
  24 /* XXX Temporary cheezoid implementation; see setitimer.c.  */
  25
  26 /* These are defined in __setitmr.c.  */
  27 extern spin_lock_t _hurd_itimer_lock;
  28 extern struct itimerval _hurd_itimerval;
  29 extern struct timeval _hurd_itimer_started;
  30
  31 static inline void
  32 subtract_timeval (struct timeval *from, const struct timeval *subtract)
  33 {
  34   from->tv_usec -= subtract->tv_usec;
  35   from->tv_sec -= subtract->tv_sec;
  36   while (from->tv_usec < 0)
  37     {
  38       --from->tv_sec;
  39       from->tv_usec += 1000000;
  40     }
  41 }
  42
  43 /* Set *VALUE to the current setting of timer WHICH.
  44    Return 0 on success, -1 on errors.  */
  45 int
  46 __getitimer (enum __itimer_which which, struct itimerval *value)
  47 {
  48   struct itimerval val;
  49   struct timeval elapsed;
  50
  51   switch (which)
  52     {
  53     default:
  54       return __hurd_fail (EINVAL);
  55
  56     case ITIMER_VIRTUAL:
  57     case ITIMER_PROF:
  58       return __hurd_fail (ENOSYS);
  59
  60     case ITIMER_REAL:
  61       break;
  62     }
  63
  64   /* Get the time now.  */
  65   {
  66      time_value_t tv;
  67      __host_get_time (__mach_host_self (), &tv);
  68      elapsed.tv_sec = tv.seconds;
  69      elapsed.tv_usec = tv.microseconds;
  70   }
  71
  72   /* Extract the current timer setting; and the time it was set, so we can
  73      calculate the time elapsed so far.  */
  74   HURD_CRITICAL_BEGIN;
  75   __spin_lock (&_hurd_itimer_lock);
  76   val = _hurd_itimerval;
  77   subtract_timeval (&elapsed, &_hurd_itimer_started);
  78   __spin_unlock (&_hurd_itimer_lock);
  79   HURD_CRITICAL_END;
  80
  81   if ((val.it_value.tv_sec | val.it_value.tv_usec) != 0)
  82     {
  83       /* There is a pending alarm set.  VAL indicates the interval it was
  84          set for, relative to the time recorded in _hurd_itimer_started.
  85          Now compensate for the time elapsed since to get the user's
  86          conception of the current value of the timer (as if the value
  87          stored decreased every microsecond).  */
  88       if (timercmp (&val.it_value, &elapsed, <))
  89         {
  90           /* Hmm.  The timer should have just gone off, but has not been
  91              reset.  This is a possible timing glitch.  The alarm will signal
  92              soon, so fabricate a value for how soon.  */
  93           val.it_value.tv_sec = 0;
  94           val.it_value.tv_usec = 10; /* Random.  */
  95         }
  96       else
  97         /* Subtract the time elapsed since the timer was set
  98            from the current timer value the user sees.  */
  99         subtract_timeval (&val.it_value, &elapsed);
 100     }
 101
 102   *value = val;
 103   return 0;
 104 }
 105
 106 weak_alias (__getitimer, getitimer)