70 lines
3.0 KiB
C
70 lines
3.0 KiB
C
/* Copyright (c) 2007, Google Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Google Inc. nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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// Taken from C++11 proposal N2660:
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// "Dynamic Initialization and Destruction with Concurrency"
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// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2660.htm
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#include <aos/threads.h>
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/// Protects global_epoch and all thread_once_t writes.
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static struct thread_mutex thread_once_mutex = THREAD_MUTEX_INITIALIZER;
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/// Signalled whenever a fast_pthread_once_t is finalized.
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static struct thread_cond thread_once_condvar = THREAD_COND_INITIALIZER;
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#define THREAD_ONCE_BEING_INITIALIZED (THREAD_ONCE_INIT - 1)
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static thread_once_t thread_once_global_epoch = 0;
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__thread thread_once_t thread_once_local_epoch;
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void thread_once_internal(thread_once_t *control, void (*func)(void)) {
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thread_once_t x = *control; // unprotected access
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if (x > thread_once_local_epoch) {
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thread_mutex_lock(&thread_once_mutex);
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if (*control == THREAD_ONCE_INIT) {
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*control = THREAD_ONCE_BEING_INITIALIZED;
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thread_mutex_unlock(&thread_once_mutex);
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(*func)();
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thread_mutex_lock(&thread_once_mutex);
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thread_once_global_epoch++;
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*control = thread_once_global_epoch;
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thread_cond_broadcast(&thread_once_condvar);
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} else {
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while (*control == THREAD_ONCE_BEING_INITIALIZED) {
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thread_cond_wait(&thread_once_condvar, &thread_once_mutex);
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}
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}
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thread_once_local_epoch = thread_once_global_epoch;
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thread_mutex_unlock(&thread_once_mutex);
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}
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}
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