| 1 | /* Creating and controlling threads.
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| 2 | Copyright (C) 2005-2021 Free Software Foundation, Inc.
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| 3 |
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| 4 | This file is free software: you can redistribute it and/or modify
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| 5 | it under the terms of the GNU Lesser General Public License as
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| 6 | published by the Free Software Foundation; either version 2.1 of the
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| 7 | License, or (at your option) any later version.
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| 8 |
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| 9 | This file is distributed in the hope that it will be useful,
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | GNU Lesser General Public License for more details.
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| 13 |
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| 14 | You should have received a copy of the GNU Lesser General Public License
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| 15 | along with this program. If not, see <https://www.gnu.org/licenses/>. */
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| 16 |
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| 17 | /* Written by Bruno Haible <bruno@clisp.org>, 2005.
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| 18 | Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-win32.h. */
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| 19 |
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| 20 | #include <config.h>
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| 21 |
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| 22 | /* Specification. */
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| 23 | #include "glthread/thread.h"
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| 24 |
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| 25 | #include <stdlib.h>
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| 26 | #include "glthread/lock.h"
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| 27 |
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| 28 | /* ========================================================================= */
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| 29 |
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| 30 | #if USE_ISOC_THREADS
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| 31 |
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| 32 | struct thrd_with_exitvalue
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| 33 | {
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| 34 | thrd_t volatile tid;
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| 35 | void * volatile exitvalue;
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| 36 | };
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| 37 |
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| 38 | /* The Thread-Specific Storage (TSS) key that allows to access each thread's
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| 39 | 'struct thrd_with_exitvalue *' pointer. */
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| 40 | static tss_t thrd_with_exitvalue_key;
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| 41 |
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| 42 | /* Initializes thrd_with_exitvalue_key.
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| 43 | This function must only be called once. */
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| 44 | static void
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| 45 | do_init_thrd_with_exitvalue_key (void)
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| 46 | {
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| 47 | if (tss_create (&thrd_with_exitvalue_key, NULL) != thrd_success)
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| 48 | abort ();
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| 49 | }
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| 50 |
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| 51 | /* Initializes thrd_with_exitvalue_key. */
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| 52 | static void
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| 53 | init_thrd_with_exitvalue_key (void)
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| 54 | {
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| 55 | static once_flag once = ONCE_FLAG_INIT;
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| 56 | call_once (&once, do_init_thrd_with_exitvalue_key);
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| 57 | }
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| 58 |
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| 59 | typedef union
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| 60 | {
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| 61 | struct thrd_with_exitvalue t;
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| 62 | struct
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| 63 | {
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| 64 | thrd_t tid; /* reserve memory for t.tid */
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| 65 | void *(*mainfunc) (void *);
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| 66 | void *arg;
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| 67 | } a;
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| 68 | }
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| 69 | main_arg_t;
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| 70 |
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| 71 | static int
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| 72 | thrd_main_func (void *pmarg)
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| 73 | {
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| 74 | /* Unpack the object that combines mainfunc and arg. */
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| 75 | main_arg_t *main_arg = (main_arg_t *) pmarg;
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| 76 | void *(*mainfunc) (void *) = main_arg->a.mainfunc;
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| 77 | void *arg = main_arg->a.arg;
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| 78 |
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| 79 | if (tss_set (thrd_with_exitvalue_key, &main_arg->t) != thrd_success)
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| 80 | abort ();
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| 81 |
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| 82 | /* Execute mainfunc, with arg as argument. */
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| 83 | {
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| 84 | void *exitvalue = mainfunc (arg);
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| 85 | /* Store the exitvalue, for use by glthread_join(). */
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| 86 | main_arg->t.exitvalue = exitvalue;
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| 87 | return 0;
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| 88 | }
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| 89 | }
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| 90 |
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| 91 | int
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| 92 | glthread_create (gl_thread_t *threadp, void *(*mainfunc) (void *), void *arg)
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| 93 | {
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| 94 | init_thrd_with_exitvalue_key ();
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| 95 | {
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| 96 | /* Combine mainfunc and arg in a single object.
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| 97 | A stack-allocated object does not work, because it would be out of
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| 98 | existence when thrd_create returns before thrd_main_func is
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| 99 | entered. So, allocate it in the heap. */
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| 100 | main_arg_t *main_arg = (main_arg_t *) malloc (sizeof (main_arg_t));
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| 101 | if (main_arg == NULL)
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| 102 | return ENOMEM;
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| 103 | main_arg->a.mainfunc = mainfunc;
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| 104 | main_arg->a.arg = arg;
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| 105 | switch (thrd_create ((thrd_t *) &main_arg->t.tid, thrd_main_func, main_arg))
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| 106 | {
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| 107 | case thrd_success:
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| 108 | break;
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| 109 | case thrd_nomem:
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| 110 | free (main_arg);
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| 111 | return ENOMEM;
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| 112 | default:
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| 113 | free (main_arg);
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| 114 | return EAGAIN;
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| 115 | }
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| 116 | *threadp = &main_arg->t;
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| 117 | return 0;
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| 118 | }
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| 119 | }
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| 120 |
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| 121 | gl_thread_t
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| 122 | gl_thread_self (void)
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| 123 | {
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| 124 | init_thrd_with_exitvalue_key ();
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| 125 | {
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| 126 | gl_thread_t thread =
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| 127 | (struct thrd_with_exitvalue *) tss_get (thrd_with_exitvalue_key);
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| 128 | if (thread == NULL)
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| 129 | {
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| 130 | /* This happens only in threads that have not been created through
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| 131 | glthread_create(), such as the main thread. */
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| 132 | for (;;)
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| 133 | {
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| 134 | thread =
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| 135 | (struct thrd_with_exitvalue *)
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| 136 | malloc (sizeof (struct thrd_with_exitvalue));
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| 137 | if (thread != NULL)
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| 138 | break;
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| 139 | /* Memory allocation failed. There is not much we can do. Have to
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| 140 | busy-loop, waiting for the availability of memory. */
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| 141 | {
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| 142 | struct timespec ts;
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| 143 | ts.tv_sec = 1;
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| 144 | ts.tv_nsec = 0;
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| 145 | thrd_sleep (&ts, NULL);
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| 146 | }
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| 147 | }
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| 148 | thread->tid = thrd_current ();
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| 149 | thread->exitvalue = NULL; /* just to be deterministic */
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| 150 | if (tss_set (thrd_with_exitvalue_key, thread) != thrd_success)
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| 151 | abort ();
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| 152 | }
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| 153 | return thread;
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| 154 | }
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| 155 | }
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| 156 |
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| 157 | int
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| 158 | glthread_join (gl_thread_t thread, void **return_value_ptr)
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| 159 | {
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| 160 | /* On Solaris 11.4, thrd_join crashes when the second argument we pass is
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| 161 | NULL. */
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| 162 | int dummy;
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| 163 |
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| 164 | if (thread == gl_thread_self ())
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| 165 | return EINVAL;
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| 166 | if (thrd_join (thread->tid, &dummy) != thrd_success)
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| 167 | return EINVAL;
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| 168 | if (return_value_ptr != NULL)
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| 169 | *return_value_ptr = thread->exitvalue;
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| 170 | free (thread);
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| 171 | return 0;
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| 172 | }
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| 173 |
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| 174 | _Noreturn void
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| 175 | gl_thread_exit (void *return_value)
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| 176 | {
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| 177 | gl_thread_t thread = gl_thread_self ();
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| 178 | thread->exitvalue = return_value;
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| 179 | thrd_exit (0);
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| 180 | }
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| 181 |
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| 182 | #endif
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| 183 |
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| 184 | /* ========================================================================= */
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| 185 |
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| 186 | #if USE_POSIX_THREADS || USE_ISOC_AND_POSIX_THREADS
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| 187 |
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| 188 | #include <pthread.h>
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| 189 |
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| 190 | #if defined PTW32_VERSION || defined __MVS__
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| 191 |
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| 192 | const gl_thread_t gl_null_thread /* = { .p = NULL } */;
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| 193 |
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| 194 | #endif
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| 195 |
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| 196 | #endif
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| 197 |
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| 198 | /* ========================================================================= */
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| 199 |
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| 200 | #if USE_WINDOWS_THREADS
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| 201 |
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| 202 | #endif
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| 203 |
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| 204 | /* ========================================================================= */
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| 205 |
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| 206 | gl_thread_t
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| 207 | gl_thread_create (void *(*func) (void *arg), void *arg)
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| 208 | {
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| 209 | gl_thread_t thread;
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| 210 | int ret;
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| 211 |
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| 212 | ret = glthread_create (&thread, func, arg);
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| 213 | if (ret != 0)
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| 214 | abort ();
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| 215 | return thread;
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| 216 | }
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