OSAtomicOperations.c   [plain text]

/*
 * Copyright (c) 2000-2015 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_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. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * 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_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <libkern/OSAtomic.h>
#include <kern/debug.h>
#include <machine/atomic.h>

enum {
	false	= 0,
	true	= 1
};

#ifndef NULL
#define NULL ((void *)0)
#endif

#define ATOMIC_DEBUG DEBUG

#if ATOMIC_DEBUG
#define ALIGN_TEST(p,t) do{if((uintptr_t)p&(sizeof(t)-1)) panic("Unaligned atomic pointer %p\n",p);}while(0)
#else
#define ALIGN_TEST(p,t) do{}while(0)
#endif

// 19831745 - start of big hammer!
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-qual"

/*
 * atomic operations
 *	These are _the_ atomic operations, now implemented via compiler built-ins.
 *	It is expected that this C implementation is a candidate for Link-Time-
 *	Optimization inlining, whereas the assembler implementations they replace
 *	were not.
 */

#undef OSCompareAndSwap8
Boolean OSCompareAndSwap8(UInt8 oldValue, UInt8 newValue, volatile UInt8 *address)
{
	return __c11_atomic_compare_exchange_strong((_Atomic UInt8 *)address, &oldValue, newValue,
			memory_order_acq_rel_smp, memory_order_relaxed);
}

#undef OSCompareAndSwap16
Boolean OSCompareAndSwap16(UInt16 oldValue, UInt16 newValue, volatile UInt16 *address)
{
	return __c11_atomic_compare_exchange_strong((_Atomic UInt16 *)address, &oldValue, newValue,
			memory_order_acq_rel_smp, memory_order_relaxed);
}

#undef OSCompareAndSwap
Boolean OSCompareAndSwap(UInt32 oldValue, UInt32 newValue, volatile UInt32 *address)
{
	ALIGN_TEST(address, UInt32);
	return __c11_atomic_compare_exchange_strong((_Atomic UInt32 *)address, &oldValue, newValue,
			memory_order_acq_rel_smp, memory_order_relaxed);
}

#undef OSCompareAndSwap64
Boolean OSCompareAndSwap64(UInt64 oldValue, UInt64 newValue, volatile UInt64 *address)
{
	/*
	 * _Atomic uint64 requires 8-byte alignment on all architectures.
	 * This silences the compiler cast warning.  ALIGN_TEST() verifies
	 * that the cast was legal, if defined.
	 */
	_Atomic UInt64 *aligned_addr = (_Atomic UInt64 *)(uintptr_t)address;

	ALIGN_TEST(address, UInt64);
	return __c11_atomic_compare_exchange_strong(aligned_addr, &oldValue, newValue,
			memory_order_acq_rel_smp, memory_order_relaxed);
}

#undef OSCompareAndSwapPtr
Boolean OSCompareAndSwapPtr(void *oldValue, void *newValue, void * volatile *address)
{
#if __LP64__
  return OSCompareAndSwap64((UInt64)oldValue, (UInt64)newValue, (volatile UInt64 *)address);
#else
  return OSCompareAndSwap((UInt32)oldValue, (UInt32)newValue, (volatile UInt32 *)address);
#endif
}

SInt8 OSAddAtomic8(SInt32 amount, volatile SInt8 *address)
{
	return __c11_atomic_fetch_add((_Atomic SInt8*)address, amount, memory_order_relaxed);
}

SInt16 OSAddAtomic16(SInt32 amount, volatile SInt16 *address)
{
	return __c11_atomic_fetch_add((_Atomic SInt16*)address, amount, memory_order_relaxed);
}

#undef OSAddAtomic
SInt32 OSAddAtomic(SInt32 amount, volatile SInt32 *address)
{
	ALIGN_TEST(address, UInt32);
	return __c11_atomic_fetch_add((_Atomic SInt32*)address, amount, memory_order_relaxed);
}

#undef OSAddAtomic64
SInt64 OSAddAtomic64(SInt64 amount, volatile SInt64 *address)
{
	_Atomic SInt64*	aligned_address = (_Atomic SInt64*)(uintptr_t)address;

	ALIGN_TEST(address, SInt64);
	return __c11_atomic_fetch_add(aligned_address, amount, memory_order_relaxed);
}

#undef OSAddAtomicLong
long
OSAddAtomicLong(long theAmount, volatile long *address)
{
#ifdef __LP64__
	return (long)OSAddAtomic64((SInt64)theAmount, (SInt64*)address);
#else
	return (long)OSAddAtomic((SInt32)theAmount, address);
#endif
}

#undef OSIncrementAtomic
SInt32	OSIncrementAtomic(volatile SInt32 * value)
{
	return OSAddAtomic(1, value);
}

#undef OSDecrementAtomic
SInt32	OSDecrementAtomic(volatile SInt32 * value)
{
	return OSAddAtomic(-1, value);
}

#undef OSBitAndAtomic
UInt32	OSBitAndAtomic(UInt32 mask, volatile UInt32 * value)
{
	return __c11_atomic_fetch_and((_Atomic UInt32*)value, mask, memory_order_relaxed);
}

#undef OSBitOrAtomic
UInt32	OSBitOrAtomic(UInt32 mask, volatile UInt32 * value)
{
	return __c11_atomic_fetch_or((_Atomic UInt32*)value, mask, memory_order_relaxed);
}

#undef OSBitXorAtomic
UInt32	OSBitXorAtomic(UInt32 mask, volatile UInt32 * value)
{
	return __c11_atomic_fetch_xor((_Atomic UInt32*)value, mask, memory_order_relaxed);
}

static Boolean	OSTestAndSetClear(UInt32 bit, Boolean wantSet, volatile UInt8 * startAddress)
{
	UInt8		mask = 1;
	UInt8		oldValue;
	UInt8		wantValue;
	
	startAddress += (bit / 8);
	mask <<= (7 - (bit % 8));
	wantValue = wantSet ? mask : 0;
	
	do {
		oldValue = *startAddress;
		if ((oldValue & mask) == wantValue) {
			break;
		}
	} while (! __c11_atomic_compare_exchange_strong((_Atomic UInt8 *)startAddress,
		&oldValue, (oldValue & ~mask) | wantValue, memory_order_relaxed, memory_order_relaxed));
	
	return (oldValue & mask) == wantValue;
}

Boolean OSTestAndSet(UInt32 bit, volatile UInt8 * startAddress)
{
	return OSTestAndSetClear(bit, true, startAddress);
}

Boolean OSTestAndClear(UInt32 bit, volatile UInt8 * startAddress)
{
	return OSTestAndSetClear(bit, false, startAddress);
}

/*
 * silly unaligned versions
 */

SInt8	OSIncrementAtomic8(volatile SInt8 * value)
{
	return OSAddAtomic8(1, value);
}

SInt8	OSDecrementAtomic8(volatile SInt8 * value)
{
	return OSAddAtomic8(-1, value);
}

UInt8	OSBitAndAtomic8(UInt32 mask, volatile UInt8 * value)
{
	return __c11_atomic_fetch_and((_Atomic UInt8 *)value, mask, memory_order_relaxed);
}

UInt8	OSBitOrAtomic8(UInt32 mask, volatile UInt8 * value)
{
	return __c11_atomic_fetch_or((_Atomic UInt8 *)value, mask, memory_order_relaxed);
}

UInt8	OSBitXorAtomic8(UInt32 mask, volatile UInt8 * value)
{
	return __c11_atomic_fetch_xor((_Atomic UInt8 *)value, mask, memory_order_relaxed);
}

SInt16	OSIncrementAtomic16(volatile SInt16 * value)
{
	return OSAddAtomic16(1, value);
}

SInt16	OSDecrementAtomic16(volatile SInt16 * value)
{
	return OSAddAtomic16(-1, value);
}

UInt16	OSBitAndAtomic16(UInt32 mask, volatile UInt16 * value)
{
	return __c11_atomic_fetch_and((_Atomic UInt16 *)value, mask, memory_order_relaxed);
}

UInt16	OSBitOrAtomic16(UInt32 mask, volatile UInt16 * value)
{
	return __c11_atomic_fetch_or((_Atomic UInt16 *)value, mask, memory_order_relaxed);
}

UInt16	OSBitXorAtomic16(UInt32 mask, volatile UInt16 * value)
{
	return __c11_atomic_fetch_xor((_Atomic UInt16 *)value, mask, memory_order_relaxed);
}

// 19831745 - end of big hammer!
#pragma clang diagnostic pop