lib/libthr/thread/thr_once.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice unmodified, this list of conditions, and the following
  12  *    disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include <sys/cdefs.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include "namespace.h"
  33 #include <pthread.h>
  34 #include "un-namespace.h"
  35
  36 #include "thr_private.h"
  37
  38 __weak_reference(_pthread_once, pthread_once);
  39
  40 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  41 #define ONCE_DONE               PTHREAD_DONE_INIT
  42 #define ONCE_IN_PROGRESS        0x02
  43 #define ONCE_WAIT               0x03
  44
  45 /*
  46  * POSIX:
  47  * The pthread_once() function is not a cancellation point. However,
  48  * if init_routine is a cancellation point and is canceled, the effect
  49  * on once_control shall be as if pthread_once() was never called.
  50  */
  51
  52 static void
  53 once_cancel_handler(void *arg)
  54 {
  55         pthread_once_t *once_control;
  56
  57         once_control = arg;
  58         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
  59             ONCE_NEVER_DONE))
  60                 return;
  61         atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
  62         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
  63 }
  64
  65 int
  66 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
  67 {
  68         struct pthread *curthread;
  69         int state;
  70
  71         _thr_check_init();
  72
  73         for (;;) {
  74                 state = once_control->state;
  75                 if (state == ONCE_DONE) {
  76                         atomic_thread_fence_acq();
  77                         return (0);
  78                 }
  79                 if (state == ONCE_NEVER_DONE) {
  80                         if (atomic_cmpset_int(&once_control->state, state,
  81                             ONCE_IN_PROGRESS))
  82                                 break;
  83                 } else if (state == ONCE_IN_PROGRESS) {
  84                         if (atomic_cmpset_int(&once_control->state, state,
  85                             ONCE_WAIT))
  86                                 _thr_umtx_wait_uint(&once_control->state,
  87                                     ONCE_WAIT, NULL, 0);
  88                 } else if (state == ONCE_WAIT) {
  89                         _thr_umtx_wait_uint(&once_control->state, state,
  90                             NULL, 0);
  91                 } else
  92                         return (EINVAL);
  93         }
  94
  95         curthread = _get_curthread();
  96         THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
  97         init_routine();
  98         THR_CLEANUP_POP(curthread, 0);
  99         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
 100             ONCE_DONE))
 101                 return (0);
 102         atomic_store_rel_int(&once_control->state, ONCE_DONE);
 103         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
 104         return (0);
 105 }