SPINLOCK(3) BSD Library Functions Manual SPINLOCK(3)NAME
OSSpinLockTry, OSSpinLockLock, OSSpinLockUnlock — atomic spin lock syn‐
chronization 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 vari‐
ous strategies to back off, making it immune to most priority-inversion
livelocks. But because it can spin, it may be inefficient in some situa‐
tions.
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 VALUESOSSpinLockTry() returns true if it took the lock, false if the lock was
already held.
SEE ALSOatomic(3), barrier(3)Darwin May 26, 2004 Darwin
