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Diffstat (limited to 'lib/libpthread/thread/thr_once.c')
| -rw-r--r-- | lib/libpthread/thread/thr_once.c | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/lib/libpthread/thread/thr_once.c b/lib/libpthread/thread/thr_once.c new file mode 100644 index 0000000..ad158d1 --- /dev/null +++ b/lib/libpthread/thread/thr_once.c @@ -0,0 +1,96 @@ +/* + * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by John Birrell. + * 4. Neither the name of the author nor the names of any co-contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ +#include "namespace.h" +#include <pthread.h> +#include "un-namespace.h" +#include "thr_private.h" + +__weak_reference(_pthread_once, pthread_once); + +#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT +#define ONCE_DONE PTHREAD_DONE_INIT +#define ONCE_IN_PROGRESS 0x02 +#define ONCE_MASK 0x03 + +static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER; +static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; + +/* + * POSIX: + * The pthread_once() function is not a cancellation point. However, + * if init_routine is a cancellation point and is canceled, the effect + * on once_control shall be as if pthread_once() was never called. + */ + +static void +once_cancel_handler(void *arg) +{ + pthread_once_t *once_control = arg; + + _pthread_mutex_lock(&once_lock); + once_control->state = ONCE_NEVER_DONE; + _pthread_mutex_unlock(&once_lock); + _pthread_cond_broadcast(&once_cv); +} + +int +_pthread_once(pthread_once_t *once_control, void (*init_routine) (void)) +{ + int wakeup = 0; + + if (once_control->state == ONCE_DONE) + return (0); + _pthread_mutex_lock(&once_lock); + while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS) + _pthread_cond_wait(&once_cv, &once_lock); + /* + * If previous thread was canceled, then the state still + * could be ONCE_NEVER_DONE, we need to check it again. + */ + if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) { + once_control->state = ONCE_IN_PROGRESS; + _pthread_mutex_unlock(&once_lock); + _pthread_cleanup_push(once_cancel_handler, once_control); + init_routine(); + _pthread_cleanup_pop(0); + _pthread_mutex_lock(&once_lock); + once_control->state = ONCE_DONE; + wakeup = 1; + } + _pthread_mutex_unlock(&once_lock); + if (wakeup) + _pthread_cond_broadcast(&once_cv); + return (0); +} + |
