libkern/OSAtomicQueue.h

@abstract The initialization vector for a queue head.

#define OS_ATOMIC_QUEUE_INIT { NULL, 0 }

__OSX_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_4_0)
void OSAtomicEnqueue(OSQueueHead *__list, void *__new, size_t __offset)

@abstract Enqueue an element onto a list. @discussion Memory barriers are incorporated as needed to permit thread-safe access to the queue element. @param __list The list on which you want to enqueue the element. @param __new The element to add. @param __offset The "offset" parameter is the offset (in bytes) of the link field from the beginning of the data structure being queued (<code>__new</code>). The link field should be a pointer type. The <code>__offset</code> value needs to be same for all enqueuing and dequeuing operations on the same list, even if different structure types are enqueued on that list. The use of <code>offsetset()</code>, defined in <code>stddef.h</code> is the common way to specify the <code>__offset</code> value.

__OSX_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_4_0)
void* OSAtomicDequeue(OSQueueHead *__list, size_t __offset)

@abstract Dequeue an element from a list. @discussion Memory barriers are incorporated as needed to permit thread-safe access to the queue element. @param __list The list from which you want to dequeue an element. @param __offset The "offset" parameter is the offset (in bytes) of the link field from the beginning of the data structure being dequeued (<code>__new</code>). The link field should be a pointer type. The <code>__offset</code> value needs to be same for all enqueuing and dequeuing operations on the same list, even if different structure types are enqueued on that list. The use of <code>offsetset()</code>, defined in <code>stddef.h</code> is the common way to specify the <code>__offset</code> value. IMPORTANT: the memory backing the link field of a queue element must not be unmapped after OSAtomicDequeue() returns until all concurrent calls to OSAtomicDequeue() for the same list on other threads have also returned, as they may still be accessing that memory location. @result Returns the most recently enqueued element, or <code>NULL</code> if the list is empty.