rt/timer_create.c

   1 /* Copyright (C) 2000-2023 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 License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    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; see the file COPYING.LIB.  If
  16    not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <signal.h>
  20 #include <pthread.h>
  21 #include <time.h>
  22 #include <unistd.h>
  23
  24 #include "posix-timer.h"
  25
  26
  27 /* Create new per-process timer using CLOCK.  */
  28 int
  29 timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
  30 {
  31   int retval = -1;
  32   struct timer_node *newtimer = NULL;
  33   struct thread_node *thread = NULL;
  34
  35   if (0
  36 #if defined _POSIX_CPUTIME && _POSIX_CPUTIME >= 0
  37       || clock_id == CLOCK_PROCESS_CPUTIME_ID
  38 #endif
  39 #if defined _POSIX_THREAD_CPUTIME && _POSIX_THREAD_CPUTIME >= 0
  40       || clock_id == CLOCK_THREAD_CPUTIME_ID
  41 #endif
  42       )
  43     {
  44       /* We don't allow timers for CPU clocks.  At least not in the
  45          moment.  */
  46       __set_errno (ENOTSUP);
  47       return -1;
  48     }
  49
  50   if (clock_id != CLOCK_REALTIME)
  51     {
  52       __set_errno (EINVAL);
  53       return -1;
  54     }
  55
  56   pthread_once (&__timer_init_once_control, __timer_init_once);
  57
  58   if (__timer_init_failed)
  59     {
  60       __set_errno (ENOMEM);
  61       return -1;
  62     }
  63
  64   pthread_mutex_lock (&__timer_mutex);
  65
  66   newtimer = __timer_alloc ();
  67   if (__glibc_unlikely (newtimer == NULL))
  68     {
  69       __set_errno (EAGAIN);
  70       goto unlock_bail;
  71     }
  72
  73   if (evp != NULL)
  74     newtimer->event = *evp;
  75   else
  76     {
  77       newtimer->event.sigev_notify = SIGEV_SIGNAL;
  78       newtimer->event.sigev_signo = SIGALRM;
  79       newtimer->event.sigev_value.sival_ptr = newtimer;
  80       newtimer->event.sigev_notify_function = 0;
  81     }
  82
  83   newtimer->event.sigev_notify_attributes = &newtimer->attr;
  84   newtimer->creator_pid = getpid ();
  85
  86   switch (__builtin_expect (newtimer->event.sigev_notify, SIGEV_SIGNAL))
  87     {
  88     case SIGEV_NONE:
  89     case SIGEV_SIGNAL:
  90       /* We have a global thread for delivering timed signals.
  91          If it is not running, try to start it up.  */
  92       thread = &__timer_signal_thread_rclk;
  93       if (! thread->exists)
  94         {
  95           if (__builtin_expect (__timer_thread_start (thread),
  96                                 1) < 0)
  97             {
  98               __set_errno (EAGAIN);
  99               goto unlock_bail;
 100             }
 101         }
 102       break;
 103
 104     case SIGEV_THREAD:
 105       /* Copy over thread attributes or set up default ones.  */
 106       if (evp->sigev_notify_attributes)
 107         newtimer->attr = *(pthread_attr_t *) evp->sigev_notify_attributes;
 108       else
 109         pthread_attr_init (&newtimer->attr);
 110
 111       /* Ensure thread attributes call for detached thread.  */
 112       pthread_attr_setdetachstate (&newtimer->attr, PTHREAD_CREATE_DETACHED);
 113
 114       /* Try to find existing thread having the right attributes.  */
 115       thread = __timer_thread_find_matching (&newtimer->attr, clock_id);
 116
 117       /* If no existing thread has these attributes, try to allocate one.  */
 118       if (thread == NULL)
 119         thread = __timer_thread_alloc (&newtimer->attr, clock_id);
 120
 121       /* Out of luck; no threads are available.  */
 122       if (__glibc_unlikely (thread == NULL))
 123         {
 124           __set_errno (EAGAIN);
 125           goto unlock_bail;
 126         }
 127
 128       /* If the thread is not running already, try to start it.  */
 129       if (! thread->exists
 130           && __builtin_expect (! __timer_thread_start (thread), 0))
 131         {
 132           __set_errno (EAGAIN);
 133           goto unlock_bail;
 134         }
 135       break;
 136
 137     default:
 138       __set_errno (EINVAL);
 139       goto unlock_bail;
 140     }
 141
 142   newtimer->clock = clock_id;
 143   newtimer->abstime = 0;
 144   newtimer->armed = 0;
 145   newtimer->thread = thread;
 146
 147   *timerid = timer_ptr2id (newtimer);
 148   retval = 0;
 149
 150   if (__builtin_expect (retval, 0) == -1)
 151     {
 152     unlock_bail:
 153       if (thread != NULL)
 154         __timer_thread_dealloc (thread);
 155       if (newtimer != NULL)
 156         {
 157           timer_delref (newtimer);
 158           __timer_dealloc (newtimer);
 159         }
 160     }
 161
 162   pthread_mutex_unlock (&__timer_mutex);
 163
 164   return retval;
 165 }