/* Copyright (c) 2018, 2024, Oracle and/or its affiliates. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2.0, as published by the Free Software Foundation. This program is designed to work with certain software (including but not limited to OpenSSL) that is licensed under separate terms, as designated in a particular file or component or in included license documentation. The authors of MySQL hereby grant you an additional permission to link the program and your derivative works with the separately licensed software that they have either included with the program or referenced in the documentation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0, for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ #include "sql/mdl_context_backup.h" #include "mutex_lock.h" // MUTEX_LOCK #include "mysql/psi/mysql_memory.h" // mysql_memory_register #include "mysqld_error.h" // ER_* #include "sql/sql_const.h" // LONG_TIMEOUT /** Wrapper around MDL_context class which allows to store it in backup manager's collection. Also implements MDL_context_owner interface and serves as owner for stored MDL_context. */ class MDL_context_backup_manager::MDL_context_backup : public MDL_context_owner { public: MDL_context_backup() { m_context.init(this); } ~MDL_context_backup() override { assert(!m_context.has_locks(MDL_EXPLICIT)); assert(!m_context.has_locks(MDL_STATEMENT)); m_context.release_transactional_locks(); m_context.destroy(); } public: MDL_context *get_context() { return &m_context; } private: // Begin implementation of MDL_context_owner interface. void enter_cond(mysql_cond_t *, mysql_mutex_t *, const PSI_stage_info *, PSI_stage_info *, const char *, const char *, int) override { DBUG_TRACE; return; } void exit_cond(const PSI_stage_info *, const char *, const char *, int) override { DBUG_TRACE; return; } int is_killed() const override { return false; } bool might_have_commit_order_waiters() const final { return false; } /** @warning Since there is no THD associated with This method returns nullptr unconditionally. */ THD *get_thd() override { return nullptr; } void notify_shared_lock(MDL_context_owner *, bool) override { return; } bool notify_hton_pre_acquire_exclusive(const MDL_key *, bool *) override { return false; } void notify_hton_post_release_exclusive(const MDL_key *) override { return; } uint get_rand_seed() const override { return 1; } bool is_connected(bool = false) override { return true; } // End implementation of MDL_context_owner interface. private: // MDL_context member to hold locks MDL_context m_context; }; MDL_context_backup_manager *MDL_context_backup_manager::m_single = nullptr; #ifdef HAVE_PSI_INTERFACE static PSI_mutex_key key_LOCK_mdl_context_backup_manager; static PSI_mutex_info mdl_context_backup_manager_mutexes[] = { {&key_LOCK_mdl_context_backup_manager, "LOCK_mdl_context_backup_manager", PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME}}; static PSI_memory_key key_memory_MDL_context_backup_manager; static PSI_memory_info mdl_context_backup_manager_memory[] = { {&key_memory_MDL_context_backup_manager, "MDL_context::backup_manager", 0, 0, "MDL for prepared XA trans with disconnected client."}}; void MDL_context_backup_manager::init_psi_keys(void) { const char *category = "sql"; int count = array_elements(mdl_context_backup_manager_mutexes); mysql_mutex_register(category, mdl_context_backup_manager_mutexes, count); count = static_cast(array_elements(mdl_context_backup_manager_memory)); mysql_memory_register(category, mdl_context_backup_manager_memory, count); } #endif /* HAVE_PSI_INTERFACE */ MDL_context_backup_manager::MDL_context_backup_manager(PSI_memory_key key) : m_backup_map( std::less(), Malloc_allocator>>( key)) { #ifdef HAVE_PSI_INTERFACE init_psi_keys(); #endif mysql_mutex_init(key_LOCK_mdl_context_backup_manager, &m_LOCK_mdl_context_backup, MY_MUTEX_INIT_SLOW); } bool MDL_context_backup_manager::init() { DBUG_TRACE; m_single = new (std::nothrow) MDL_context_backup_manager(key_memory_MDL_context_backup_manager); return m_single == nullptr; } MDL_context_backup_manager &MDL_context_backup_manager::instance() { assert(m_single != nullptr); return *m_single; } void MDL_context_backup_manager::destroy() { DBUG_TRACE; delete m_single; m_single = nullptr; } MDL_context_backup_manager::~MDL_context_backup_manager() { mysql_mutex_destroy(&m_LOCK_mdl_context_backup); } bool MDL_context_backup_manager::check_key_exist( const MDL_context_backup_key &key_obj) { MUTEX_LOCK(guard, &m_LOCK_mdl_context_backup); return m_backup_map.find(key_obj) != m_backup_map.end(); } bool MDL_context_backup_manager::create_backup(const MDL_context *context, const uchar *key, const size_t keylen) { DBUG_TRACE; try { MDL_context_backup_key key_obj(key, keylen); /* Since this method is called as part of THD cleaning up, every XA transaction must be present in the m_backup_map only once. In other words, it mustn't be present any element for specified xid when this method called. Check that this invariant is satisfied. */ assert(!check_key_exist(key_obj)); auto element = std::make_unique(); if (element->get_context()->clone_tickets(context, MDL_TRANSACTION)) return true; MUTEX_LOCK(guard, &m_LOCK_mdl_context_backup); // Do this before inserting into the map, to avoid having to remove DBUG_EXECUTE_IF("xaprep_create_mdl_backup_fail", { throw std::bad_alloc(); }); m_backup_map.emplace(std::move(key_obj), std::move(element)); } catch (std::bad_alloc &) { my_error(ER_OUT_OF_RESOURCES, MYF(ME_FATALERROR)); return true; } return false; } bool MDL_context_backup_manager::create_backup(MDL_request_list *mdl_requests, const uchar *key, const size_t keylen) { DBUG_TRACE; bool result = false; try { MDL_context_backup_key key_obj(key, keylen); /* Check for presence a record with specified key in the collection of MDL_context_backup elements. It is ok to already have a record with the same xid value in this collection. Presence of a element with the same value of xid at the moment of invocation the method create_backup() is stipulated by the fact that ha_recover() can be called twice (and hence the same list of prepared XA transactions is processed twice). First time it can be called from transaction coordinator (that is either from binlog or tc_log_mmap) and second time it is called unconditionally from init_server_components(). Therefore presence of an entry in the cache at the moment when the method create_backup() is called second time shouldn't be considered as error. */ if (check_key_exist(key_obj)) return false; std::unique_ptr element(new (std::nothrow) MDL_context_backup()); if (element == nullptr) { my_error(ER_OUTOFMEMORY, MYF(ME_FATALERROR), sizeof(element)); return true; } if (element->get_context()->acquire_locks(mdl_requests, LONG_TIMEOUT)) return true; MUTEX_LOCK(guard, &m_LOCK_mdl_context_backup); m_backup_map.emplace(key_obj, std::move(element)); } catch (std::bad_alloc &) { result = true; } return result; } bool MDL_context_backup_manager::restore_backup(MDL_context *mdl_context, const uchar *key, const size_t keylen) { bool res = false; MDL_context_backup *element; DBUG_TRACE; MUTEX_LOCK(guard, &m_LOCK_mdl_context_backup); auto result = m_backup_map.find(MDL_context_backup_key(key, keylen)); if (result != m_backup_map.end()) { element = result->second.get(); res = mdl_context->clone_tickets(element->get_context(), MDL_TRANSACTION); } return res; } void MDL_context_backup_manager::delete_backup(const uchar *key, const size_t keylen) { DBUG_TRACE; MUTEX_LOCK(guard, &m_LOCK_mdl_context_backup); m_backup_map.erase(MDL_context_backup_key(key, keylen)); }