`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`.)
{
    LOCK2(cs_main, cs_LastBlockFile);
    if (::ChainActive().Tip() == nullptr || nPruneTarget == 0) {
        return;
    }
    if ((uint64_t)::ChainActive().Tip()->nHeight <= nPruneAfterHeight) {
        return;
    }
    unsigned int nLastBlockWeCanPrune = ::ChainActive().Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
    uint64_t nCurrentUsage = CalculateCurrentUsage();
    
    
    
    uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
    uint64_t nBytesToPrune;
    int count=0;
    if (nCurrentUsage + nBuffer >= nPruneTarget) {