lib/libkse/thread/thr_once.c

   1 /*
   2  * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
   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  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD$
  30  */
  31
  32 #include "namespace.h"
  33 #include <pthread.h>
  34 #include "un-namespace.h"
  35 #include "thr_private.h"
  36
  37 __weak_reference(_pthread_once, pthread_once);
  38
  39 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  40 #define ONCE_DONE               PTHREAD_DONE_INIT
  41 #define ONCE_IN_PROGRESS        0x02
  42 #define ONCE_MASK               0x03
  43
  44 static pthread_mutex_t          once_lock = PTHREAD_MUTEX_INITIALIZER;
  45 static pthread_cond_t           once_cv = PTHREAD_COND_INITIALIZER;
  46
  47 /*
  48  * POSIX:
  49  * The pthread_once() function is not a cancellation point. However,
  50  * if init_routine is a cancellation point and is canceled, the effect
  51  * on once_control shall be as if pthread_once() was never called.
  52  */
  53
  54 static void
  55 once_cancel_handler(void *arg)
  56 {
  57         pthread_once_t *once_control = arg;
  58
  59         _pthread_mutex_lock(&once_lock);
  60         once_control->state = ONCE_NEVER_DONE;
  61         _pthread_mutex_unlock(&once_lock);
  62         _pthread_cond_broadcast(&once_cv);
  63 }
  64
  65 int
  66 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
  67 {
  68         struct pthread *curthread;
  69         int wakeup = 0;
  70
  71         if (once_control->state == ONCE_DONE)
  72                 return (0);
  73         _pthread_mutex_lock(&once_lock);
  74         while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
  75                 _pthread_cond_wait(&once_cv, &once_lock);
  76         /*
  77          * If previous thread was canceled, then the state still
  78          * could be ONCE_NEVER_DONE, we need to check it again.
  79          */
  80         if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
  81                 once_control->state = ONCE_IN_PROGRESS;
  82                 _pthread_mutex_unlock(&once_lock);
  83                 curthread = _get_curthread();
  84                 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
  85                 init_routine();
  86                 THR_CLEANUP_POP(curthread, 0);
  87                 _pthread_mutex_lock(&once_lock);
  88                 once_control->state = ONCE_DONE;
  89                 wakeup = 1;
  90         }
  91         _pthread_mutex_unlock(&once_lock);
  92         if (wakeup)
  93                 _pthread_cond_broadcast(&once_cv);
  94         return (0);
  95 }
  96