/* * Copyright (c) 2004 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ #ifndef _OSATOMIC_H_ #define _OSATOMIC_H_ #include <stddef.h> #include <sys/cdefs.h> #include <stdint.h> #include <stdbool.h> /* These are the preferred versions of the atomic and synchronization operations. * Their implementation is customized at boot time for the platform, including * late-breaking errata fixes as necessary. They are thread safe. * * WARNING: all addresses passed to these functions must be "naturally aligned", ie * int32_t's must be 32-bit aligned (low 2 bits of address zero), and int64_t's * must be 64-bit aligned (low 3 bits of address zero.) * * Note that some versions of the atomic functions incorporate memory barriers, * and some do not. Barriers strictly order memory access on a weakly-ordered * architecture such as PPC. All loads and stores executed in sequential program * order before the barrier will complete before any load or store executed after * the barrier. On a uniprocessor, the barrier operation is typically a nop. * On a multiprocessor, the barrier can be quite expensive. * * Most code will want to use the barrier functions to insure that memory shared * between threads is properly synchronized. For example, if you want to initialize * a shared data structure and then atomically increment a variable to indicate * that the initialization is complete, then you MUST use OSAtomicIncrement32Barrier() * to ensure that the stores to your data structure complete before the atomic add. * Likewise, the consumer of that data structure MUST use OSAtomicDecrement32Barrier(), * in order to ensure that their loads of the structure are not executed before * the atomic decrement. On the other hand, if you are simply incrementing a global * counter, then it is safe and potentially faster to use OSAtomicIncrement32(). * * If you are unsure which version to use, prefer the barrier variants as they are * safer. * * The spinlock and queue operations always incorporate a barrier. */ __BEGIN_DECLS /* Arithmetic functions. They return the new value. All the "or", "and", and "xor" * operations, and the barrier forms of add, are layered on top of compare-and-swap. */ int32_t OSAtomicAdd32( int32_t theAmount, int32_t *theValue ); int32_t OSAtomicAdd32Barrier( int32_t theAmount, int32_t *theValue ); inline static int32_t OSAtomicIncrement32( int32_t *theValue ) { return OSAtomicAdd32( 1, theValue); } inline static int32_t OSAtomicIncrement32Barrier( int32_t *theValue ) { return OSAtomicAdd32Barrier( 1, theValue); } inline static int32_t OSAtomicDecrement32( int32_t *theValue ) { return OSAtomicAdd32( -1, theValue); } inline static int32_t OSAtomicDecrement32Barrier( int32_t *theValue ) { return OSAtomicAdd32Barrier( -1, theValue); } int32_t OSAtomicOr32( uint32_t theMask, uint32_t *theValue ); int32_t OSAtomicOr32Barrier( uint32_t theMask, uint32_t *theValue ); int32_t OSAtomicAnd32( uint32_t theMask, uint32_t *theValue ); int32_t OSAtomicAnd32Barrier( uint32_t theMask, uint32_t *theValue ); int32_t OSAtomicXor32( uint32_t theMask, uint32_t *theValue ); int32_t OSAtomicXor32Barrier( uint32_t theMask, uint32_t *theValue ); #if defined(__ppc64__) || defined(__i386__) int64_t OSAtomicAdd64( int64_t theAmount, int64_t *theValue ); int64_t OSAtomicAdd64Barrier( int64_t theAmount, int64_t *theValue ); inline static int64_t OSAtomicIncrement64( int64_t *theValue ) { return OSAtomicAdd64( 1, theValue); } inline static int64_t OSAtomicIncrement64Barrier( int64_t *theValue ) { return OSAtomicAdd64Barrier( 1, theValue); } inline static int64_t OSAtomicDecrement64( int64_t *theValue ) { return OSAtomicAdd64( -1, theValue); } inline static int64_t OSAtomicDecrement64Barrier( int64_t *theValue ) { return OSAtomicAdd64Barrier( -1, theValue); } #endif /* defined(__ppc64__) || defined(__i386__) */ /* Compare and swap. They return true if the swap occured. */ bool OSAtomicCompareAndSwap32( int32_t oldValue, int32_t newValue, int32_t *theValue ); bool OSAtomicCompareAndSwap32Barrier( int32_t oldValue, int32_t newValue, int32_t *theValue ); #if defined(__ppc64__) || defined(__i386__) bool OSAtomicCompareAndSwap64( int64_t oldValue, int64_t newValue, int64_t *theValue ); bool OSAtomicCompareAndSwap64Barrier( int64_t oldValue, int64_t newValue, int64_t *theValue ); #endif /* defined(__ppc64__) || defined(__i386__) */ /* Test and set. They return the original value of the bit, and operate on bit (0x80>>(n&7)) * in byte ((char*)theAddress + (n>>3)). They are layered on top of the compare-and-swap * operation. */ bool OSAtomicTestAndSet( uint32_t n, void *theAddress ); bool OSAtomicTestAndSetBarrier( uint32_t n, void *theAddress ); bool OSAtomicTestAndClear( uint32_t n, void *theAddress ); bool OSAtomicTestAndClearBarrier( uint32_t n, void *theAddress ); /* Spinlocks. These use memory barriers as required to synchronize access to shared * memory protected by the lock. The lock operation spins, but employs various strategies * to back off if the lock is held, making it immune to most priority-inversion livelocks. * The try operation immediately returns false if the lock was held, true if it took the * lock. The convention is that unlocked is zero, locked is nonzero. */ #define OS_SPINLOCK_INIT 0 typedef int32_t OSSpinLock; bool OSSpinLockTry( OSSpinLock *lock ); void OSSpinLockLock( OSSpinLock *lock ); void OSSpinLockUnlock( OSSpinLock *lock ); /* Memory barrier. It is both a read and write barrier. */ void OSMemoryBarrier( void ); __END_DECLS #endif /* _OSATOMIC_H_ */