Merge pull request #2737

935f7462 blockchain: do not lock the blockchain lock for simple DB getters (moneromooo-monero)

src/cryptonote_core/blockchain.cpp

@@ -139,14 +139,20 @@ Blockchain::Blockchain(tx_memory_pool& tx_pool) :
 bool Blockchain::have_tx(const crypto::hash &id) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   return m_db->tx_exists(id);
 }
 //------------------------------------------------------------------
 bool Blockchain::have_tx_keyimg_as_spent(const crypto::key_image &key_im) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   return  m_db->has_key_image(key_im);
 }
 //------------------------------------------------------------------
@@ -287,7 +293,10 @@ bool Blockchain::scan_outputkeys_for_indexes(size_t tx_version, const txin_to_ke
 uint64_t Blockchain::get_current_blockchain_height() const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   return m_db->height();
 }
 //------------------------------------------------------------------
@@ -571,7 +580,10 @@ crypto::hash Blockchain::get_tail_id(uint64_t& height) const
 crypto::hash Blockchain::get_tail_id() const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   return m_db->top_block_hash();
 }
 //------------------------------------------------------------------
@@ -633,7 +645,10 @@ bool Blockchain::get_short_chain_history(std::list<crypto::hash>& ids) const
 crypto::hash Blockchain::get_block_id_by_height(uint64_t height) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   try
   {
     return m_db->get_block_hash_from_height(height);
@@ -1928,7 +1943,10 @@ bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qbloc
 uint64_t Blockchain::block_difficulty(uint64_t i) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   try
   {
     return m_db->get_block_difficulty(i);
@@ -2209,7 +2227,10 @@ bool Blockchain::handle_block_to_main_chain(const block& bl, block_verification_
 size_t Blockchain::get_total_transactions() const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  // WARNING: this function does not take m_blockchain_lock, and thus should only call read only
+  // m_db functions which do not depend on one another (ie, no getheight + gethash(height-1), as
+  // well as not accessing class members, even read only (ie, m_invalid_blocks). The caller must
+  // lock if it is otherwise needed.
   return m_db->get_tx_count();
 }
 //------------------------------------------------------------------