barrier(3) [osx man page]

BARRIER(3)						   BSD Library Functions Manual 						BARRIER(3)

NAME

     OSMemoryBarrier -- memory barrier to order loads and stores

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <libkern/OSAtomic.h>

     void
     OSMemoryBarrier(void);

DESCRIPTION

     OSMemoryBarrier() strictly orders memory accesses in a weakly ordered memory model such as with PowerPC, by creating a barrier.  All loads
     and stores executed in sequential program order before the barrier will complete with respect to the memory coherence mechanism, before any
     load or store executed after the barrier.	Used with an atomic operation, the barrier can be used to create custom synchronization protocols
     as an alternative to the spinlock or queue/dequeue operations.  Note that this barrier does not order uncached loads and stores.  On a
     uniprocessor, the barrier operation is typically optimized into a nop.

SEE ALSO

     atomic(3), spinlock(3)

Darwin								   May 26, 2004 							    Darwin

MEMBAR_OPS(3)						   BSD Library Functions Manual 					     MEMBAR_OPS(3)

NAME

     membar_ops, membar_enter, membar_exit, membar_producer, membar_consumer, membar_sync -- memory access barrier operations

SYNOPSIS

     #include <sys/atomic.h>

     void
     membar_enter(void);

     void
     membar_exit(void);

     void
     membar_producer(void);

     void
     membar_consumer(void);

     void
     membar_sync(void);

DESCRIPTION

     The membar_ops family of functions provide memory access barrier operations necessary for synchronization in multiprocessor execution envi-
     ronments that have relaxed load and store order.

     membar_enter()
	  Any store preceding membar_enter() will reach global visibility before all loads and stores following it.

	  membar_enter() is typically used in code that implements locking primitives to ensure that a lock protects its data.

     membar_exit()
	  All loads and stores preceding membar_exit() will reach global visibility before any store that follows it.

	  membar_exit() is typically used in code that implements locking primitives to ensure that a lock protects its data.

     membar_producer()
	  All stores preceding the memory barrier will reach global visibility before any stores after the memory barrier reach global visibility.

     membar_consumer()
	  All loads preceding the memory barrier will complete before any loads after the memory barrier complete.

     membar_sync()
	  All loads and stores preceding the memory barrier will complete and reach global visibility before any loads and stores after the memory
	  barrier complete and reach global visibility.

SEE ALSO

     atomic_ops(3)

HISTORY

     The membar_ops functions first appeared in NetBSD 5.0.

BSD
								 February 11, 2007							       BSD