Does Mac OS X have pthread_spinlock_t type? - macos

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
};

Answer 2

Try using OSSpinLock instead. Documentation is here: http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man3/spinlock.3.html

Answer 3

If the performance of your lock is not critical, pthread_mutex_t can be used as a drop replacement for pthread_spinlock_t, which makes porting easy.

Answer 4

I have used instead (that is natively supported by OS X intel)
pthread_rwlock_t lock;
pthread_rwlock_init
pthread_rwlock_wrlock
pthread_rwlock_unlock
And that works very fine as well