LoadChainTip requires cs_main to be locked. Under some conditions, it may call ActivateBestChain. However, ActivateBestChain requires cs_main NOT to be taken when called.
{
    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) {