RtlBeginReadTickLock

__int64 __fastcall RtlBeginReadTickLock(__int64 *a1){
  __int64 result; 

  while( 1 )
  {
    result = *a1;
    if( (*a1 & 1) == 0 )
      break;
    _mm_pause();
  }
  return result;
}

Referenced by:

KeCpuSetQueryUnparkRecommendation
KeQueryCpuSetInformation
KiComputeCpuSetAffinityMask
KiComputeThreadAffinity
RtlGetMultiTimePrecise