82 lines
3.1 KiB
C++
82 lines
3.1 KiB
C++
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/*
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* Copyright (C) 2015 The Android Open Source Project
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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
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* are met:
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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 copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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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
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <pthread.h>
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#include "private/bionic_lock.h"
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// User-level spinlocks can be hazardous to battery life on Android.
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// We implement a simple compromise that behaves mostly like a spinlock,
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// but prevents excessively long spinning.
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struct pthread_spinlock_internal_t {
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Lock lock;
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};
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static_assert(sizeof(pthread_spinlock_t) == sizeof(pthread_spinlock_internal_t),
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"pthread_spinlock_t should actually be pthread_spinlock_internal_t.");
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static_assert(alignof(pthread_spinlock_t) >= 4,
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"pthread_spinlock_t should fulfill the alignment of pthread_spinlock_internal_t.");
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static inline pthread_spinlock_internal_t* __get_internal_spinlock(pthread_spinlock_t* lock) {
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return reinterpret_cast<pthread_spinlock_internal_t*>(lock);
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}
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int pthread_spin_init(pthread_spinlock_t* lock_interface, int pshared) {
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pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
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lock->lock.init(pshared);
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return 0;
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}
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int pthread_spin_destroy(pthread_spinlock_t* lock_interface) {
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pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
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return lock->lock.trylock() ? 0 : EBUSY;
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}
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int pthread_spin_trylock(pthread_spinlock_t* lock_interface) {
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pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
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return lock->lock.trylock() ? 0 : EBUSY;
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}
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int pthread_spin_lock(pthread_spinlock_t* lock_interface) {
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pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
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for (int i = 0; i < 10000; ++i) {
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if (lock->lock.trylock()) {
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return 0;
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}
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}
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lock->lock.lock();
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return 0;
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}
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int pthread_spin_unlock(pthread_spinlock_t* lock_interface) {
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pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
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lock->lock.unlock();
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return 0;
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}
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