Does Mac OS X have pthread_spinlock_t type?

Question

I didn't find it in Mac, but almost all Linux os support it.. Any one knows how to port it to mac?

Answer 1

Here is drop in replacement code. You should be able to put this in a header file and drop it in your project.

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;
}

See discussion, and Github source

EDIT: Here's a class that works on all OSes that includes a workaround for missing pthread spinlocks on OSX:

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
};