Mac OS X是否有pthread_spinlock_t类型？

Question

我在Mac上找不到它，但几乎所有的Linux操作系统都支持它。有人知道如何将其移植到Mac吗？

- JustQieTry

Answer 1

这是可直接替换的代码。您应该能够将其放入头文件中并将其放入您的项目中。

typedef int pthread_spinlock_t;

int pthread_spin_init(pthread_spinlock_t *lock, int pshared) {
    __asm__ __volatile__ ("" ::: "memory");
    *lock = 0;
    return 0;
}

int pthread_spin_destroy(pthread_spinlock_t *lock) {
    return 0;
}

int pthread_spin_lock(pthread_spinlock_t *lock) {
    while (1) {
        int i;
        for (i=0; i < 10000; i++) {
            if (__sync_bool_compare_and_swap(lock, 0, 1)) {
                return 0;
            }
        }
        sched_yield();
    }
}

int pthread_spin_trylock(pthread_spinlock_t *lock) {
    if (__sync_bool_compare_and_swap(lock, 0, 1)) {
        return 0;
    }
    return EBUSY;
}

int pthread_spin_unlock(pthread_spinlock_t *lock) {
    __asm__ __volatile__ ("" ::: "memory");
    *lock = 0;
    return 0;
}

请参见讨论和Github源代码。编辑：这里有一个在所有操作系统上都可以使用的类，包括对OSX缺少pthread自旋锁的解决方法。

class Spinlock
{
private:    //private copy-ctor and assignment operator ensure the lock never gets copied, which might cause issues.
    Spinlock operator=(const Spinlock & asdf);
    Spinlock(const Spinlock & asdf);
#ifdef __APPLE__
    OSSpinLock m_lock;
public:
    Spinlock()
    : m_lock(0)
    {}
    void lock() {
        OSSpinLockLock(&m_lock);
    }
    bool try_lock() {
        return OSSpinLockTry(&m_lock);
    }
    void unlock() {
        OSSpinLockUnlock(&m_lock);
    }
#else
    pthread_spinlock_t m_lock;
public:
    Spinlock() {
        pthread_spin_init(&m_lock, 0);
    }

    void lock() {
        pthread_spin_lock(&m_lock);
    }
    bool try_lock() {
        int ret = pthread_spin_trylock(&m_lock);
        return ret != 16;   //EBUSY == 16, lock is already taken
    }
    void unlock() {
        pthread_spin_unlock(&m_lock);
    }
    ~Spinlock() {
        pthread_spin_destroy(&m_lock);
    }
#endif
};

- leecbaker

Answer 2

尝试使用OSSpinLock代替。文档在这里：http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man3/spinlock.3.html

- Catfish_Man

---

老实说，目前os_unfair_lock更好的选择。请参阅https://developer.apple.com/documentation/os/1646466-os_unfair_lock_lock?language=objc等... - Catfish_Man

Answer 3

如果您的锁的性能不是关键问题，可以使用pthread_mutex_t作为pthread_spinlock_t的替代品，这样可以轻松进行移植。

- Mark Waller

Answer 4

我已经使用了OS X intel原生支持的替代方法

1. pthread_rwlock_t lock;
2. pthread_rwlock_init
3. pthread_rwlock_wrlock
4. pthread_rwlock_unlock

这也很好地工作了。

- Danouchka