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(_thr_once, pthread_once);
  39 __weak_reference(_thr_once, _pthread_once);
  40
  41 #define ONCE_NEVER_DONE         PTHREAD_NEEDS_INIT
  42 #define ONCE_DONE               PTHREAD_DONE_INIT
  43 #define ONCE_IN_PROGRESS        0x02
  44 #define ONCE_WAIT               0x03
  45
  46 /*
  47  * POSIX:
  48  * The pthread_once() function is not a cancellation point. However,
  49  * if init_routine is a cancellation point and is canceled, the effect
  50  * on once_control shall be as if pthread_once() was never called.
  51  */
  52
  53 static void
  54 once_cancel_handler(void *arg)
  55 {
  56         pthread_once_t *once_control;
  57
  58         once_control = arg;
  59         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
  60             ONCE_NEVER_DONE))
  61                 return;
  62         atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
  63         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
  64 }
  65
  66 int
  67 _thr_once(pthread_once_t *once_control, void (*init_routine)(void))
  68 {
  69         struct pthread *curthread;
  70         int state;
  71
  72         _thr_check_init();
  73
  74         for (;;) {
  75                 state = once_control->state;
  76                 if (state == ONCE_DONE) {
  77                         atomic_thread_fence_acq();
  78                         return (0);
  79                 }
  80                 if (state == ONCE_NEVER_DONE) {
  81                         if (atomic_cmpset_int(&once_control->state, state,
  82                             ONCE_IN_PROGRESS))
  83                                 break;
  84                 } else if (state == ONCE_IN_PROGRESS) {
  85                         if (atomic_cmpset_int(&once_control->state, state,
  86                             ONCE_WAIT))
  87                                 _thr_umtx_wait_uint(&once_control->state,
  88                                     ONCE_WAIT, NULL, 0);
  89                 } else if (state == ONCE_WAIT) {
  90                         _thr_umtx_wait_uint(&once_control->state, state,
  91                             NULL, 0);
  92                 } else
  93                         return (EINVAL);
  94         }
  95
  96         curthread = _get_curthread();
  97         THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
  98         init_routine();
  99         THR_CLEANUP_POP(curthread, 0);
 100         if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
 101             ONCE_DONE))
 102                 return (0);
 103         atomic_store_rel_int(&once_control->state, ONCE_DONE);
 104         _thr_umtx_wake(&once_control->state, INT_MAX, 0);
 105         return (0);
 106 }