windows 自旋锁的实现

VOID
KxAcquireSpinLock ( __inout PKSPIN_LOCK SpinLock)
{
        //设置SpinLock指定位,并返回原值
        //如果原值为0,表示没有上锁,直接返回
        //如果原值为1,表示已经上锁,进入函数
    if (InterlockedBitTestAndSet64((LONG64 *)SpinLock, 0))
    {
        
        KxWaitForSpinLockAndAcquire(SpinLock);
    }

    return;
}

DECLSPEC_NOINLINE
ULONG64
KxWaitForSpinLockAndAcquire (__inout PKSPIN_LOCK SpinLock)
{
    do {
        do {
            KeYieldProcessor();
        } while (*(volatile LONG64 *)SpinLock != 0);//当锁被占用时,循环,内存循环

    //锁被释放.再次置位并探测原值, 不一定刚好是当前线程获得了        
    } while(InterlockedBitTestAndSet64((LONG64 *)SpinLock, 0));//返回原值为1时,继续循环

}

汇编实现:

lock bts qword ptr [rcx], 0        ;判断原值
jnb     short RETURN                ; jump short if not below (CF=0)

WAIT:
        pause;
        mov     rax, [rcx]
        test    rax, rax
        jnz    wait                     ;为1,继续停机等待
        lock bts qword ptr [rcx], 0    ;
        jb      short WAIT             ;CF为1,跳转,说明原值为1,表示并没有获取到锁,继续停机

RETURN:
        ret;