From 0fd6ccef2164f8a40988df16d37175a16ed27128 Mon Sep 17 00:00:00 2001 From: moneromooo-monero Date: Sat, 13 Jun 2020 14:20:20 +0000 Subject: [PATCH] blockchain: fix timestamp/difficulty cache getting out of sync The cache is discarded when a block is popped, but then gets rebuilt when the difficulty for next block is requested. While this is all properly locked, it does not take into account the delay caused by a database transaction being only committed (and thus its effects made visible to other threads) later on, which means another thread could request difficulty between the pop and the commit, which would end up using stale database view to build the cache, but that cache would not be invalidated again when the transaction gets committed, which would cause the cache to not match the new database data. To fix this, we now keep track of when the cache is invalidated so we can invalidate it again upon database transaction commit to ensure it gets calculated again with fresh data next time it is nedeed. --- src/cryptonote_core/blockchain.cpp | 17 ++++++++++++++++- src/cryptonote_core/blockchain.h | 1 + 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp index ec701eb2c..4a3e2f08f 100644 --- a/src/cryptonote_core/blockchain.cpp +++ b/src/cryptonote_core/blockchain.cpp @@ -86,7 +86,7 @@ DISABLE_VS_WARNINGS(4267) //------------------------------------------------------------------ Blockchain::Blockchain(tx_memory_pool& tx_pool) : - m_db(), m_tx_pool(tx_pool), m_hardfork(NULL), m_timestamps_and_difficulties_height(0), m_current_block_cumul_weight_limit(0), m_current_block_cumul_weight_median(0), + m_db(), m_tx_pool(tx_pool), m_hardfork(NULL), m_timestamps_and_difficulties_height(0), m_reset_timestamps_and_difficulties_height(true), m_current_block_cumul_weight_limit(0), m_current_block_cumul_weight_median(0), m_enforce_dns_checkpoints(false), m_max_prepare_blocks_threads(4), m_db_sync_on_blocks(true), m_db_sync_threshold(1), m_db_sync_mode(db_async), m_db_default_sync(false), m_fast_sync(true), m_show_time_stats(false), m_sync_counter(0), m_bytes_to_sync(0), m_cancel(false), m_long_term_block_weights_window(CRYPTONOTE_LONG_TERM_BLOCK_WEIGHT_WINDOW_SIZE), m_long_term_effective_median_block_weight(0), @@ -427,6 +427,7 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline if (num_popped_blocks > 0) { m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; m_hardfork->reorganize_from_chain_height(get_current_blockchain_height()); uint64_t top_block_height; crypto::hash top_block_hash = get_tail_id(top_block_height); @@ -567,6 +568,7 @@ block Blockchain::pop_block_from_blockchain() CRITICAL_REGION_LOCAL(m_blockchain_lock); m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; block popped_block; std::vector popped_txs; @@ -644,6 +646,7 @@ bool Blockchain::reset_and_set_genesis_block(const block& b) LOG_PRINT_L3("Blockchain::" << __func__); CRITICAL_REGION_LOCAL(m_blockchain_lock); m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; invalidate_block_template_cache(); m_db->reset(); m_db->drop_alt_blocks(); @@ -858,6 +861,8 @@ start: // pop the oldest one from the list. This only requires 1x read per height instead // of doing 735 (DIFFICULTY_BLOCKS_COUNT). bool check = false; + if (m_reset_timestamps_and_difficulties_height) + m_timestamps_and_difficulties_height = 0; if (m_timestamps_and_difficulties_height != 0 && ((height - m_timestamps_and_difficulties_height) == 1) && m_timestamps.size() >= DIFFICULTY_BLOCKS_COUNT) { uint64_t index = height - 1; @@ -981,6 +986,7 @@ bool Blockchain::rollback_blockchain_switching(std::list& original_chain, } m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; // remove blocks from blockchain until we get back to where we should be. while (m_db->height() != rollback_height) @@ -1017,6 +1023,7 @@ bool Blockchain::switch_to_alternative_blockchain(std::list CRITICAL_REGION_LOCAL(m_blockchain_lock); m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; // if empty alt chain passed (not sure how that could happen), return false CHECK_AND_ASSERT_MES(alt_chain.size(), false, "switch_to_alternative_blockchain: empty chain passed"); @@ -1706,6 +1713,7 @@ bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id LOG_PRINT_L3("Blockchain::" << __func__); CRITICAL_REGION_LOCAL(m_blockchain_lock); m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = true; uint64_t block_height = get_block_height(b); if(0 == block_height) { @@ -4385,7 +4393,14 @@ bool Blockchain::cleanup_handle_incoming_blocks(bool force_sync) try { if (m_batch_success) + { m_db->batch_stop(); + if (m_reset_timestamps_and_difficulties_height) + { + m_timestamps_and_difficulties_height = 0; + m_reset_timestamps_and_difficulties_height = false; + } + } else m_db->batch_abort(); success = true; diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h index 3a89cc5df..82051ecd4 100644 --- a/src/cryptonote_core/blockchain.h +++ b/src/cryptonote_core/blockchain.h @@ -1067,6 +1067,7 @@ namespace cryptonote std::vector m_timestamps; std::vector m_difficulties; uint64_t m_timestamps_and_difficulties_height; + bool m_reset_timestamps_and_difficulties_height; uint64_t m_long_term_block_weights_window; uint64_t m_long_term_effective_median_block_weight; mutable crypto::hash m_long_term_block_weights_cache_tip_hash;