rt/timer_settime.c

   1 /* Copyright (C) 2000-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Kaz Kylheku <kaz@ashi.footprints.net>.
   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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If
  17    not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <pthread.h>
  21 #include <time.h>
  22
  23 #include "posix-timer.h"
  24
  25
  26 /* Set timer TIMERID to VALUE, returning old value in OVLAUE.  */
  27 int
  28 timer_settime (timer_t timerid, int flags, const struct itimerspec *value,
  29                struct itimerspec *ovalue)
  30 {
  31   struct timer_node *timer;
  32   struct thread_node *thread = NULL;
  33   struct timespec now;
  34   int have_now = 0, need_wakeup = 0;
  35   int retval = -1;
  36
  37   timer = timer_id2ptr (timerid);
  38   if (timer == NULL)
  39     {
  40       __set_errno (EINVAL);
  41       goto bail;
  42     }
  43
  44   if (! valid_nanoseconds (value->it_interval.tv_nsec)
  45       || ! valid_nanoseconds (value->it_value.tv_nsec))
  46     {
  47       __set_errno (EINVAL);
  48       goto bail;
  49     }
  50
  51   /* Will need to know current time since this is a relative timer;
  52      might as well make the system call outside of the lock now! */
  53
  54   if ((flags & TIMER_ABSTIME) == 0)
  55     {
  56       __clock_gettime (timer->clock, &now);
  57       have_now = 1;
  58     }
  59
  60   pthread_mutex_lock (&__timer_mutex);
  61   timer_addref (timer);
  62
  63   /* One final check of timer validity; this one is possible only
  64      until we have the mutex, because it accesses the inuse flag. */
  65
  66   if (! timer_valid(timer))
  67     {
  68       __set_errno (EINVAL);
  69       goto unlock_bail;
  70     }
  71
  72   if (ovalue != NULL)
  73     {
  74       ovalue->it_interval = timer->value.it_interval;
  75
  76       if (timer->armed)
  77         {
  78           if (! have_now)
  79             {
  80               pthread_mutex_unlock (&__timer_mutex);
  81               __clock_gettime (timer->clock, &now);
  82               have_now = 1;
  83               pthread_mutex_lock (&__timer_mutex);
  84               timer_addref (timer);
  85             }
  86
  87           timespec_sub (&ovalue->it_value, &timer->expirytime, &now);
  88         }
  89       else
  90         {
  91           ovalue->it_value.tv_sec = 0;
  92           ovalue->it_value.tv_nsec = 0;
  93         }
  94     }
  95
  96   timer->value = *value;
  97
  98   list_unlink_ip (&timer->links);
  99   timer->armed = 0;
 100
 101   thread = timer->thread;
 102
 103   /* A value of { 0, 0 } causes the timer to be stopped. */
 104   if (value->it_value.tv_sec != 0
 105       || __builtin_expect (value->it_value.tv_nsec != 0, 1))
 106     {
 107       if ((flags & TIMER_ABSTIME) != 0)
 108         /* The user specified the expiration time.  */
 109         timer->expirytime = value->it_value;
 110       else
 111         timespec_add (&timer->expirytime, &now, &value->it_value);
 112
 113       /* Only need to wake up the thread if timer is inserted
 114          at the head of the queue. */
 115       if (thread != NULL)
 116         need_wakeup = __timer_thread_queue_timer (thread, timer);
 117       timer->armed = 1;
 118     }
 119
 120   retval = 0;
 121
 122 unlock_bail:
 123   timer_delref (timer);
 124   pthread_mutex_unlock (&__timer_mutex);
 125
 126 bail:
 127   if (thread != NULL && need_wakeup)
 128     __timer_thread_wakeup (thread);
 129
 130   return retval;
 131 }