lib/libthr/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 unmodified, this list of conditions, and the following
  10  *    disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  *
  26  * $FreeBSD$
  27  *
  28  */
  29
  30 #include "namespace.h"
  31 #include <pthread.h>
  32 #include "un-namespace.h"
  33
  34 #include "thr_private.h"
  35
  36 __weak_reference(_pthread_once, pthread_once);
  37
  38 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  39 #define ONCE_DONE               PTHREAD_DONE_INIT
  40 #define ONCE_IN_PROGRESS        0x02
  41 #define ONCE_WAIT               0x03
  42
  43 /*
  44  * POSIX:
  45  * The pthread_once() function is not a cancellation point. However,
  46  * if init_routine is a cancellation point and is canceled, the effect
  47  * on once_control shall be as if pthread_once() was never called.
  48  */
  49
  50 static void
  51 once_cancel_handler(void *arg)
  52 {
  53         pthread_once_t *once_control = arg;
  54
  55         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_NEVER_DONE))
  56                 return;
  57         atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
  58         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
  59 }
  60
  61 int
  62 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
  63 {
  64         struct pthread *curthread;
  65         int state;
  66
  67         _thr_check_init();
  68
  69         for (;;) {
  70                 state = once_control->state;
  71                 if (state == ONCE_DONE)
  72                         return (0);
  73                 if (state == ONCE_NEVER_DONE) {
  74                         if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_IN_PROGRESS))
  75                                 break;
  76                 } else if (state == ONCE_IN_PROGRESS) {
  77                         if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_WAIT))
  78                                 _thr_umtx_wait_uint(&once_control->state, ONCE_WAIT, NULL, 0);
  79                 } else if (state == ONCE_WAIT) {
  80                         _thr_umtx_wait_uint(&once_control->state, state, NULL, 0);
  81                 } else
  82                         return (EINVAL);
  83         }
  84
  85         curthread = _get_curthread();
  86         THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
  87         init_routine();
  88         THR_CLEANUP_POP(curthread, 0);
  89         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_DONE))
  90                 return (0);
  91         atomic_store_rel_int(&once_control->state, ONCE_DONE);
  92         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
  93         return (0);
  94 }
  95
  96 void
  97 _thr_once_init()
  98 {
  99 }