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blockchain: fix block template creation race 

If two create_block_template are called at nearly the same time,
and a block is added at nearly the same time, this could happen:

- the blockchain top block is B0
- thread 1 enters create_block_template, takes blockchain lock
- thread 1 creates a fresh block referencing prev block B0
- thread 1 releases blockchain lock
- thread 0 adds a new block
- thread 0 enters create_block_template
- thread 0 updates block template
- thread 1 takes txpool lock and continues creating block template
- thread 1 overwrites block template with previous data
This commit is contained in:
moneromooo-monero 2019-02-18 15:43:08 +00:00 committed by wowario
parent 362ecad06c
commit 0622741c03
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GPG Key ID: 24DCBE762DE9C111
1 changed files with 5 additions and 5 deletions
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10
src/cryptonote_core/blockchain.cpp
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@ -1264,7 +1264,10 @@ bool Blockchain::create_block_template(block& b, const account_public_address& m
uint64_t already_generated_coins; uint64_t already_generated_coins;
uint64_t pool_cookie; uint64_t pool_cookie;
CRITICAL_REGION_BEGIN(m_blockchain_lock); m_tx_pool.lock();
const auto txpool_unlocker = epee::misc_utils::create_scope_leave_handler([&]() { m_tx_pool.unlock(); });
CRITICAL_REGION_LOCAL(m_blockchain_lock);
height = m_db->height(); height = m_db->height();
if (m_btc_valid) { if (m_btc_valid) {
// The pool cookie is atomic. The lack of locking is OK, as if it changes // The pool cookie is atomic. The lack of locking is OK, as if it changes
@ -1300,8 +1303,6 @@ bool Blockchain::create_block_template(block& b, const account_public_address& m
median_weight = m_current_block_cumul_weight_limit / 2; median_weight = m_current_block_cumul_weight_limit / 2;
already_generated_coins = m_db->get_block_already_generated_coins(height - 1); already_generated_coins = m_db->get_block_already_generated_coins(height - 1);
CRITICAL_REGION_END();
size_t txs_weight; size_t txs_weight;
uint64_t fee; uint64_t fee;
if (!m_tx_pool.fill_block_template(b, median_weight, already_generated_coins, txs_weight, fee, expected_reward, m_hardfork->get_current_version())) if (!m_tx_pool.fill_block_template(b, median_weight, already_generated_coins, txs_weight, fee, expected_reward, m_hardfork->get_current_version()))
@ -1312,7 +1313,6 @@ bool Blockchain::create_block_template(block& b, const account_public_address& m
#if defined(DEBUG_CREATE_BLOCK_TEMPLATE) #if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
size_t real_txs_weight = 0; size_t real_txs_weight = 0;
uint64_t real_fee = 0; uint64_t real_fee = 0;
CRITICAL_REGION_BEGIN(m_tx_pool.m_transactions_lock);
for(crypto::hash &cur_hash: b.tx_hashes) for(crypto::hash &cur_hash: b.tx_hashes)
{ {
auto cur_res = m_tx_pool.m_transactions.find(cur_hash); auto cur_res = m_tx_pool.m_transactions.find(cur_hash);
@ -1356,7 +1356,7 @@ bool Blockchain::create_block_template(block& b, const account_public_address& m
{ {
LOG_ERROR("Creating block template: error: wrongly calculated fee"); LOG_ERROR("Creating block template: error: wrongly calculated fee");
} }
CRITICAL_REGION_END();
MDEBUG("Creating block template: height " << height << MDEBUG("Creating block template: height " << height <<
", median weight " << median_weight << ", median weight " << median_weight <<
", already generated coins " << already_generated_coins << ", already generated coins " << already_generated_coins <<