1fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui/*
2fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * Copyright (C) 2015 The Android Open Source Project
3fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * All rights reserved.
4fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *
5fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * Redistribution and use in source and binary forms, with or without
6fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * modification, are permitted provided that the following conditions
7fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * are met:
8fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *  * Redistributions of source code must retain the above copyright
9fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *    notice, this list of conditions and the following disclaimer.
10fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *  * Redistributions in binary form must reproduce the above copyright
11fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *    notice, this list of conditions and the following disclaimer in
12fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *    the documentation and/or other materials provided with the
13fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *    distribution.
14fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui *
15fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui * SUCH DAMAGE.
27fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui */
28fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui#include <pthread.h>
29fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
30fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui#include "private/bionic_lock.h"
31fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
32fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui// User-level spinlocks can be hazardous to battery life on Android.
33fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui// We implement a simple compromise that behaves mostly like a spinlock,
34fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui// but prevents excessively long spinning.
35fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
36fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuistruct pthread_spinlock_internal_t {
37fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  Lock lock;
38fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui};
39fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
40fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuistatic_assert(sizeof(pthread_spinlock_t) == sizeof(pthread_spinlock_internal_t),
41fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui              "pthread_spinlock_t should actually be pthread_spinlock_internal_t.");
42fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
43fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuistatic_assert(alignof(pthread_spinlock_t) >= 4,
44fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui              "pthread_spinlock_t should fulfill the alignment of pthread_spinlock_internal_t.");
45fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
46fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuistatic inline pthread_spinlock_internal_t* __get_internal_spinlock(pthread_spinlock_t* lock) {
47fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return reinterpret_cast<pthread_spinlock_internal_t*>(lock);
48fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
49fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
50fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuiint pthread_spin_init(pthread_spinlock_t* lock_interface, int pshared) {
51fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
52fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  lock->lock.init(pshared);
53fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return 0;
54fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
55fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
56fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuiint pthread_spin_destroy(pthread_spinlock_t* lock_interface) {
57fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
58fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return lock->lock.trylock() ? 0 : EBUSY;
59fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
60fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
61fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuiint pthread_spin_trylock(pthread_spinlock_t* lock_interface) {
62fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
63fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return lock->lock.trylock() ? 0 : EBUSY;
64fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
65fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
66fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuiint pthread_spin_lock(pthread_spinlock_t* lock_interface) {
67fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
68fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  for (int i = 0; i < 10000; ++i) {
69fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui    if (lock->lock.trylock()) {
70fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui      return 0;
71fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui    }
72fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  }
73fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  lock->lock.lock();
74fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return 0;
75fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
76fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui
77fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cuiint pthread_spin_unlock(pthread_spinlock_t* lock_interface) {
78fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
79fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  lock->lock.unlock();
80fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui  return 0;
81fe3a83a9343f0e4ff654f09ef8ffc8a773c7c105Yabin Cui}
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