1 /*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28 #include <pthread.h>
29
30 #include "private/bionic_lock.h"
31
32 // User-level spinlocks can be hazardous to battery life on Android.
33 // We implement a simple compromise that behaves mostly like a spinlock,
34 // but prevents excessively long spinning.
35
36 struct pthread_spinlock_internal_t {
37 Lock lock;
38 };
39
40 static_assert(sizeof(pthread_spinlock_t) == sizeof(pthread_spinlock_internal_t),
41 "pthread_spinlock_t should actually be pthread_spinlock_internal_t.");
42
43 static_assert(alignof(pthread_spinlock_t) >= 4,
44 "pthread_spinlock_t should fulfill the alignment of pthread_spinlock_internal_t.");
45
__get_internal_spinlock(pthread_spinlock_t * lock)46 static inline pthread_spinlock_internal_t* __get_internal_spinlock(pthread_spinlock_t* lock) {
47 return reinterpret_cast<pthread_spinlock_internal_t*>(lock);
48 }
49
pthread_spin_init(pthread_spinlock_t * lock_interface,int pshared)50 int pthread_spin_init(pthread_spinlock_t* lock_interface, int pshared) {
51 pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
52 lock->lock.init(pshared);
53 return 0;
54 }
55
pthread_spin_destroy(pthread_spinlock_t * lock_interface)56 int pthread_spin_destroy(pthread_spinlock_t* lock_interface) {
57 pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
58 return lock->lock.trylock() ? 0 : EBUSY;
59 }
60
pthread_spin_trylock(pthread_spinlock_t * lock_interface)61 int pthread_spin_trylock(pthread_spinlock_t* lock_interface) {
62 pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
63 return lock->lock.trylock() ? 0 : EBUSY;
64 }
65
pthread_spin_lock(pthread_spinlock_t * lock_interface)66 int pthread_spin_lock(pthread_spinlock_t* lock_interface) {
67 pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
68 for (int i = 0; i < 10000; ++i) {
69 if (lock->lock.trylock()) {
70 return 0;
71 }
72 }
73 lock->lock.lock();
74 return 0;
75 }
76
pthread_spin_unlock(pthread_spinlock_t * lock_interface)77 int pthread_spin_unlock(pthread_spinlock_t* lock_interface) {
78 pthread_spinlock_internal_t* lock = __get_internal_spinlock(lock_interface);
79 lock->lock.unlock();
80 return 0;
81 }
82