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/***
This file is part of PulseAudio.
Copyright 2006 Lennart Poettering
PulseAudio is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License,
or (at your option) any later version.
PulseAudio is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with PulseAudio; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <pulsecore/macro.h>
#include <pulsecore/mutex.h>
#include "once.h"
pa_bool_t pa_once_begin(pa_once *control) {
pa_mutex *m;
pa_assert(control);
if (pa_atomic_load(&control->done))
return FALSE;
pa_atomic_inc(&control->ref);
/* Caveat: We have to make sure that the once func has completed
* before returning, even if the once func is not actually
* executed by us. Hence the awkward locking. */
for (;;) {
if ((m = pa_atomic_ptr_load(&control->mutex))) {
/* The mutex is stored in locked state, hence let's just
* wait until it is unlocked */
pa_mutex_lock(m);
pa_assert(pa_atomic_load(&control->done));
pa_once_end(control);
return FALSE;
}
pa_assert_se(m = pa_mutex_new(FALSE, FALSE));
pa_mutex_lock(m);
if (pa_atomic_ptr_cmpxchg(&control->mutex, NULL, m))
return TRUE;
pa_mutex_unlock(m);
pa_mutex_free(m);
}
}
void pa_once_end(pa_once *control) {
pa_mutex *m;
pa_assert(control);
pa_atomic_store(&control->done, 1);
pa_assert_se(m = pa_atomic_ptr_load(&control->mutex));
pa_mutex_unlock(m);
if (pa_atomic_dec(&control->ref) <= 1) {
pa_assert_se(pa_atomic_ptr_cmpxchg(&control->mutex, m, NULL));
pa_mutex_free(m);
}
}
/* Not reentrant -- how could it be? */
void pa_run_once(pa_once *control, pa_once_func_t func) {
pa_assert(control);
pa_assert(func);
if (pa_once_begin(control)) {
func();
pa_once_end(control);
}
}
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