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, raxjnz    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;