_InterlockedCompareExchange
內部函數
Microsoft 特定的
進行相互鎖定的比較和交換。
語法
long _InterlockedCompareExchange(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_acq(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_HLEAcquire(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_HLERelease(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_nf(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_np(
long volatile * Destination,
long Exchange,
long Comparand
);
long _InterlockedCompareExchange_rel(
long volatile * Destination,
long Exchange,
long Comparand
);
char _InterlockedCompareExchange8(
char volatile * Destination,
char Exchange,
char Comparand
);
char _InterlockedCompareExchange8_acq(
char volatile * Destination,
char Exchange,
char Comparand
);
char _InterlockedCompareExchange8_nf(
char volatile * Destination,
char Exchange,
char Comparand
);
char _InterlockedCompareExchange8_rel(
char volatile * Destination,
char Exchange,
char Comparand
);
short _InterlockedCompareExchange16(
short volatile * Destination,
short Exchange,
short Comparand
);
short _InterlockedCompareExchange16_acq(
short volatile * Destination,
short Exchange,
short Comparand
);
short _InterlockedCompareExchange16_nf(
short volatile * Destination,
short Exchange,
short Comparand
);
short _InterlockedCompareExchange16_np(
short volatile * Destination,
short Exchange,
short Comparand
);
short _InterlockedCompareExchange16_rel(
short volatile * Destination,
short Exchange,
short Comparand
);
__int64 _InterlockedCompareExchange64(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_acq(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_HLEAcquire (
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_HLERelease(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_nf(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_np(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
__int64 _InterlockedCompareExchange64_rel(
__int64 volatile * Destination,
__int64 Exchange,
__int64 Comparand
);
參數
Destination
[in, out]目的地值的指標。 會忽略正負號。
Exchange
[in]Exchange 值。 會忽略正負號。
Comparand
[in]要與 所 Destination
指向之值比較的值。 會忽略正負號。
傳回值
傳回值是指針所 Destination
指向的初始值。
需求
內建 | 架構 | 頁首 |
---|---|---|
_InterlockedCompareExchange 、 、 _InterlockedCompareExchange8 、 _InterlockedCompareExchange16 _InterlockedCompareExchange64 |
x86、ARM、x64、ARM64 | <intrin.h> |
_InterlockedCompareExchange_acq 、_InterlockedCompareExchange_nf 、_InterlockedCompareExchange_rel 、_InterlockedCompareExchange8_acq 、_InterlockedCompareExchange8_nf 、_InterlockedCompareExchange8_rel 、_InterlockedCompareExchange16_acq _InterlockedCompareExchange16_nf _InterlockedCompareExchange16_rel 、_InterlockedCompareExchange64_acq 、、、 _InterlockedCompareExchange64_nf _InterlockedCompareExchange64_rel |
ARM、ARM64 | <intrin.h> |
_InterlockedCompareExchange_np 、 、 _InterlockedCompareExchange16_np _InterlockedCompareExchange64_np |
x64 | <intrin.h> |
_InterlockedCompareExchange_HLEAcquire 、 、 _InterlockedCompareExchange_HLERelease 、 _InterlockedCompareExchange64_HLEAcquire _InterlockedCompareExchange64_HLERelease |
x86、x64 | <immintrin.h> |
備註
_InterlockedCompareExchange
會使用 值對 所Destination
Comparand
指向的值執行不可部分完成的比較。 如果 Destination
值等於 Comparand
值,則 Exchange
值會儲存在 Destination
所指定的位址。 否則,不會執行任何作業。
_InterlockedCompareExchange
提供 Win32 Windows SDK InterlockedCompareExchange
函式的編譯程式內建支援。
有數種變化 _InterlockedCompareExchange
會根據所牽涉的數據類型以及使用處理器特定的取得或發行語意而有所不同。
雖然函_InterlockedCompareExchange
式在 32 位整數值上運作,_InterlockedCompareExchange8
但會以 8 位long
整數值運作、_InterlockedCompareExchange16
在 16 位short
整數值上運作,並以 _InterlockedCompareExchange64
64 位整數值運作。 如需 128 位值類似內部函數的詳細資訊,請參閱 _InterlockedCompareExchange128
。
在所有 ARM 平臺上,使用內建和_acq
_rel
後綴取得和發行語意,例如在重要區段的開頭和結尾。 具有 (“無柵欄”) 後綴的 ARM 內部 _nf
函數不會作為記憶體屏障。
搭配 _np
(「不預先擷取」) 字尾使用內建函式,可避免編譯器插入可能的預先提取作業。
在支援 Hardware Lock Elision (HLE) 指令的 Intel 平台上,搭配 _HLEAcquire
和 _HLERelease
字尾的內建函式會包含對處理器的提示,提示其可以藉由消除硬體中鎖定寫入 (lock write) 的階段以加速效能。 如果在不支援 HLE 的平臺上呼叫這些內部函數,則會忽略提示。
這些常式僅以內建函式的形式供您使用。
範例
在下列範例中,_InterlockedCompareExchange
會用於簡單的低層級執行緒同步處理。 方法有其限制,作為多線程程式設計的基礎;其呈現方式說明內建的一般用法。 為求最佳結果,請使用 Windows API。 如需多線程程式設計的詳細資訊,請參閱 撰寫多線程 Win32 程式。
// intrinExample.cpp
// compile with: /EHsc /O2
// Simple example of using _Interlocked* intrinsics to
// do manual synchronization
//
// Add [-DSKIP_LOCKING] to the command line to disable
// the locking. This will cause the threads to execute out
// of sequence.
#define _CRT_RAND_S
#include "windows.h"
#include <iostream>
#include <queue>
#include <intrin.h>
using namespace std;
// --------------------------------------------------------------------
// if defined, will not do any locking on shared data
//#define SKIP_LOCKING
// A common way of locking using _InterlockedCompareExchange.
// Refer to other sources for a discussion of the many issues
// involved. For example, this particular locking scheme performs well
// when lock contention is low, as the while loop overhead is small and
// locks are acquired very quickly, but degrades as many callers want
// the lock and most threads are doing a lot of interlocked spinning.
// There are also no guarantees that a caller will ever acquire the
// lock.
namespace MyInterlockedIntrinsicLock
{
typedef unsigned LOCK, *PLOCK;
#pragma intrinsic(_InterlockedCompareExchange, _InterlockedExchange)
enum {LOCK_IS_FREE = 0, LOCK_IS_TAKEN = 1};
void Lock(PLOCK pl)
{
#if !defined(SKIP_LOCKING)
// If *pl == LOCK_IS_FREE, it is set to LOCK_IS_TAKEN
// atomically, so only 1 caller gets the lock.
// If *pl == LOCK_IS_TAKEN,
// the result is LOCK_IS_TAKEN, and the while loop keeps spinning.
while (_InterlockedCompareExchange((long *)pl,
LOCK_IS_TAKEN, // exchange
LOCK_IS_FREE) // comparand
== LOCK_IS_TAKEN)
{
// spin!
}
// This will also work.
//while (_InterlockedExchange(pl, LOCK_IS_TAKEN) ==
// LOCK_IS_TAKEN)
//{
// // spin!
//}
// At this point, the lock is acquired.
#endif
}
void Unlock(PLOCK pl) {
#if !defined(SKIP_LOCKING)
_InterlockedExchange((long *)pl, LOCK_IS_FREE);
#endif
}
}
// ------------------------------------------------------------------
// Data shared by threads
queue<int> SharedQueue;
MyInterlockedIntrinsicLock::LOCK SharedLock;
int TicketNumber;
// ------------------------------------------------------------------
DWORD WINAPI
ProducerThread(
LPVOID unused
)
{
unsigned int randValue;
while (1) {
// Acquire shared data. Enter critical section.
MyInterlockedIntrinsicLock::Lock(&SharedLock);
//cout << ">" << TicketNumber << endl;
SharedQueue.push(TicketNumber++);
// Release shared data. Leave critical section.
MyInterlockedIntrinsicLock::Unlock(&SharedLock);
rand_s(&randValue);
Sleep(randValue % 20);
}
return 0;
}
DWORD WINAPI
ConsumerThread(
LPVOID unused
)
{
while (1) {
// Acquire shared data. Enter critical section
MyInterlockedIntrinsicLock::Lock(&SharedLock);
if (!SharedQueue.empty()) {
int x = SharedQueue.front();
cout << "<" << x << endl;
SharedQueue.pop();
}
// Release shared data. Leave critical section
MyInterlockedIntrinsicLock::Unlock(&SharedLock);
unsigned int randValue;
rand_s(&randValue);
Sleep(randValue % 20);
}
return 0;
}
int main(
void
)
{
const int timeoutTime = 500;
int unused1, unused2;
HANDLE threads[4];
// The program creates 4 threads:
// two producer threads adding to the queue
// and two consumers taking data out and printing it.
threads[0] = CreateThread(NULL,
0,
ProducerThread,
&unused1,
0,
(LPDWORD)&unused2);
threads[1] = CreateThread(NULL,
0,
ConsumerThread,
&unused1,
0,
(LPDWORD)&unused2);
threads[2] = CreateThread(NULL,
0,
ProducerThread,
&unused1,
0,
(LPDWORD)&unused2);
threads[3] = CreateThread(NULL,
0,
ConsumerThread,
&unused1,
0,
(LPDWORD)&unused2);
WaitForMultipleObjects(4, threads, TRUE, timeoutTime);
return 0;
}
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END Microsoft 特定的
另請參閱
_InterlockedCompareExchange128
_InterlockedCompareExchangePointer
內建函式
編譯器內建函式
關鍵字
與 x86 編譯器衝突