NAME
OSSpinLockTry, OSSpinLockLock, OSSpinLockUnlock – deprecated atomic spin lock synchronization primitives
SYNOPSIS
#include <libkern/OSAtomic.h>
bool
OSSpinLockTry(OSSpinLock *lock);
void
OSSpinLockLock(OSSpinLock *lock);
void
OSSpinLockUnlock(OSSpinLock *lock);
DESCRIPTION
These are deprecated interfaces for userspace spinlocks, provided for compatibility with legacy code. These interfaces should no longer be used, particularily in situations where threads of differing priorities may contend on the same spinlock.
The interfaces in ⟨os/lock.h⟩ should be used instead in cases where a very low-level lock primitive is required. In general however, using higher level synchronization primitives such as those provided by the pthread or dispatch subsystems are preferred.
The OSSpinLock operations use memory barriers to synchronize access to shared memory protected by the lock. Preemption is possible while the lock is held.
OSSpinLock is an integer type. The convention is that unlocked is zero, and locked is nonzero. Locks must be naturally aligned and cannot be in cache-inhibited memory.
OSSpinLockLock() will spin if the lock is already held, but employs various strategies to back off. Because it can spin, it will generally be less cpu and power efficient than other synchronization primitives.
OSSpinLockTry() immediately returns false if the lock was held, true if it took the lock. It does not spin.
OSSpinLockUnlock() unconditionally unlocks the lock by zeroing it.
RETURN VALUES
OSSpinLockTry() returns true if it took the lock, false if the lock was already held.