lib/libthread_xu/thread/thr_once.c

   1 /*
   2  * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  *
  25  */
  26
  27 #include "namespace.h"
  28 #include <pthread.h>
  29 #include "un-namespace.h"
  30
  31 #include "thr_private.h"
  32
  33 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  34 #define ONCE_DONE               PTHREAD_DONE_INIT
  35 #define ONCE_IN_PROGRESS        0x02
  36 #define ONCE_MASK               0x03
  37
  38 static pthread_mutex_t          once_lock = PTHREAD_MUTEX_INITIALIZER;
  39 static pthread_cond_t           once_cv = PTHREAD_COND_INITIALIZER;
  40
  41 /*
  42  * POSIX:
  43  * The pthread_once() function is not a cancellation point. However,
  44  * if init_routine is a cancellation point and is canceled, the effect
  45  * on once_control shall be as if pthread_once() was never called.
  46  */
  47
  48 static void
  49 once_cancel_handler(void *arg)
  50 {
  51         pthread_once_t *once_control = arg;
  52
  53         _pthread_mutex_lock(&once_lock);
  54         once_control->state = ONCE_NEVER_DONE;
  55         _pthread_mutex_unlock(&once_lock);
  56         _pthread_cond_broadcast(&once_cv);
  57 }
  58
  59 int
  60 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
  61 {
  62         int wakeup = 0;
  63
  64         if (once_control->state == ONCE_DONE)
  65                 return (0);
  66         _pthread_mutex_lock(&once_lock);
  67         while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
  68                 _pthread_cond_wait(&once_cv, &once_lock);
  69         /*
  70          * If previous thread was canceled, then the state still
  71          * could be ONCE_NEVER_DONE, we need to check it again.
  72          */
  73         if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
  74                 once_control->state = ONCE_IN_PROGRESS;
  75                 _pthread_mutex_unlock(&once_lock);
  76                 _pthread_cleanup_push(once_cancel_handler, once_control);
  77                 init_routine();
  78                 _pthread_cleanup_pop(0);
  79                 _pthread_mutex_lock(&once_lock);
  80                 once_control->state = ONCE_DONE;
  81                 wakeup = 1;
  82         }
  83         _pthread_mutex_unlock(&once_lock);
  84         if (wakeup)
  85                 _pthread_cond_broadcast(&once_cv);
  86         return (0);
  87 }
  88
  89 __strong_reference(_pthread_once, pthread_once);