OSAtomic-v4.c   [plain text]

/*
 * 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@
 */

#include <libkern/OSAtomic.h>
#include <arm/arch.h>


#if !defined(_ARM_ARCH_6)

/*
 * The only atomic operation ARMv4T provides (atomic swap) is not
 * sufficient for the general 32-bit arithmetic and compare-and-swap
 * operations OSAtomic is supposed to provide.  So we use a global
 * spin lock around all operations.
 *
 * Since we have only a single, in-order, CPU, we do not need
 * memory barriers for data.
 */

static OSSpinLock _atomic_lock = OS_SPINLOCK_INIT;

int32_t	OSAtomicAdd32( int32_t theAmount, int32_t *theValue )
{
    int32_t result;

    OSSpinLockLock(&_atomic_lock);
    result = (*theValue += theAmount);
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

int32_t	OSAtomicAdd32Barrier( int32_t theAmount, int32_t *theValue )
{
    return OSAtomicAdd32(theAmount, theValue);
}

int32_t	OSAtomicOr32( uint32_t theMask, uint32_t *theValue )
{
    int32_t result;

    OSSpinLockLock(&_atomic_lock);
    result = (*theValue |= theMask);
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

int32_t	OSAtomicOr32Barrier( uint32_t theMask, uint32_t *theValue )
{
    return OSAtomicOr32(theMask, theValue);
}

int32_t	OSAtomicAnd32( uint32_t theMask, uint32_t *theValue )
{
    int32_t result;

    OSSpinLockLock(&_atomic_lock);
    result = (*theValue &= theMask);
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

int32_t	OSAtomicAnd32Barrier( uint32_t theMask, uint32_t *theValue )
{
    return OSAtomicAnd32(theMask, theValue);
}

int32_t	OSAtomicXor32( uint32_t theMask, uint32_t *theValue )
{
    int32_t result;

    OSSpinLockLock(&_atomic_lock);
    result = (*theValue ^= theMask);
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

int32_t	OSAtomicXor32Barrier( uint32_t theMask, uint32_t *theValue )
{
    return OSAtomicXor32(theMask, theValue);
}

bool	OSAtomicCompareAndSwap32( int32_t oldValue, int32_t newValue, int32_t *theValue )
{
    bool result;
    
    OSSpinLockLock(&_atomic_lock);
    result = (*theValue == oldValue);
    if (result) *theValue = newValue;
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

bool    OSAtomicCompareAndSwap32Barrier( int32_t oldValue, int32_t newValue, int32_t *theValue )
{
    return OSAtomicCompareAndSwap32(oldValue, newValue, theValue);
}

bool    OSAtomicTestAndSet( uint32_t n, void *theAddress )
{
    char *byteAddress = ((char*)theAddress + (n>>3));
    uint32_t byteBit = (0x80>>(n&7));
    bool result;

    OSSpinLockLock(&_atomic_lock);
    result = *byteAddress & byteBit;
    *byteAddress |= byteBit;
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

bool    OSAtomicTestAndSetBarrier( uint32_t n, void *theAddress )
{
    return OSAtomicTestAndSet(n, theAddress);
}

bool    OSAtomicTestAndClear( uint32_t n, void *theAddress )
{
    char *byteAddress = ((char*)theAddress + (n>>3));
    uint32_t byteBit = (0x80>>(n&7));
    bool result;

    OSSpinLockLock(&_atomic_lock);
    result = *byteAddress & byteBit;
    *byteAddress &= (~byteBit);
    OSSpinLockUnlock(&_atomic_lock);

    return result;
}

bool    OSAtomicTestAndClearBarrier( uint32_t n, void *theAddress )
{
    return OSAtomicTestAndClear(n, theAddress);
}

void    OSMemoryBarrier( void )
{
    return;
}

#endif /* !defined(_ARM_ARCH_6) */