`RewindBlockIndex` reads `chainActive` (via `ChainActive()`) without holding `cs_main`:

https://github.com/bitcoin/bitcoin/blob/b2a6b0216192b6e8428f1a80b47f5178fccb961a/src/validation.cpp#L4314-L4331

(Please note that callers of `RewindBlockIndex` are _not_ allowed to hold `cs_main` since `RewindBlockIndex` indirectly calls `LimitValidationInterfaceQueue`.)
{
    AssertLockHeld(cs_main);
    
    
    
    
    
    
    flags = std::max(flags, 0);
    
    
    
    
    
    
    const int nBlockHeight = ::ChainActive().Height() + 1;
    
    
    
    
    
    const int64_t nBlockTime = (flags & LOCKTIME_MEDIAN_TIME_PAST)
                             ? ::ChainActive().Tip()->GetMedianTimePast()
                             : GetAdjustedTime();
    return IsFinalTx(tx, nBlockHeight, nBlockTime);
}
bool TestLockPointValidity(const LockPoints* lp)