osspinlocktry(3) [osx man page]

SPINLOCK(3)						   BSD Library Functions Manual 					       SPINLOCK(3)

NAME

     OSSpinLockTry, OSSpinLockLock, OSSpinLockUnlock -- atomic spin lock synchronization primitives

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <libkern/OSAtomic.h>

     bool
     OSSpinLockTry(OSSpinLock *lock);

     void
     OSSpinLockLock(OSSpinLock *lock);

     void
     OSSpinLockUnlock(OSSpinLock *lock);

DESCRIPTION

     Spin locks are a simple, fast, thread-safe synchronization primitive that is suitable in situations where contention is expected to be low.
     The spinlock 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, making it immune to most priority-inver-
     sion livelocks.  But because it can spin, it may be inefficient in some situations.

     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.

SEE ALSO

     atomic(3), barrier(3)

Darwin								   May 26, 2004 							    Darwin

SPINLOCK_DEPRECATED(3)					   BSD Library Functions Manual 				    SPINLOCK_DEPRECATED(3)

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.

SEE ALSO

     atomic(3), atomic_deprecated(3)

Darwin								   May 26, 2004 							    Darwin