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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by John Birrell.
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD$
  33  */
  34 #include "namespace.h"
  35 #include <pthread.h>
  36 #include "un-namespace.h"
  37 #include "thr_private.h"
  38
  39 LT10_COMPAT_PRIVATE(_pthread_once);
  40 LT10_COMPAT_DEFAULT(pthread_once);
  41
  42 __weak_reference(_pthread_once, pthread_once);
  43
  44 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  45 #define ONCE_DONE               PTHREAD_DONE_INIT
  46 #define ONCE_IN_PROGRESS        0x02
  47 #define ONCE_MASK               0x03
  48
  49 static pthread_mutex_t          once_lock = PTHREAD_MUTEX_INITIALIZER;
  50 static pthread_cond_t           once_cv = PTHREAD_COND_INITIALIZER;
  51
  52 /*
  53  * POSIX:
  54  * The pthread_once() function is not a cancellation point. However,
  55  * if init_routine is a cancellation point and is canceled, the effect
  56  * on once_control shall be as if pthread_once() was never called.
  57  */
  58
  59 static void
  60 once_cancel_handler(void *arg)
  61 {
  62         pthread_once_t *once_control = arg;
  63
  64         _pthread_mutex_lock(&once_lock);
  65         once_control->state = ONCE_NEVER_DONE;
  66         _pthread_mutex_unlock(&once_lock);
  67         _pthread_cond_broadcast(&once_cv);
  68 }
  69
  70 int
  71 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
  72 {
  73         struct pthread *curthread;
  74         int wakeup = 0;
  75
  76         if (once_control->state == ONCE_DONE)
  77                 return (0);
  78         _pthread_mutex_lock(&once_lock);
  79         while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
  80                 _pthread_cond_wait(&once_cv, &once_lock);
  81         /*
  82          * If previous thread was canceled, then the state still
  83          * could be ONCE_NEVER_DONE, we need to check it again.
  84          */
  85         if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
  86                 once_control->state = ONCE_IN_PROGRESS;
  87                 _pthread_mutex_unlock(&once_lock);
  88                 curthread = _get_curthread();
  89                 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
  90                 init_routine();
  91                 THR_CLEANUP_POP(curthread, 0);
  92                 _pthread_mutex_lock(&once_lock);
  93                 once_control->state = ONCE_DONE;
  94                 wakeup = 1;
  95         }
  96         _pthread_mutex_unlock(&once_lock);
  97         if (wakeup)
  98                 _pthread_cond_broadcast(&once_cv);
  99         return (0);
 100 }
 101