service_locking.h

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/*
  Copyright (c) 2015, 2025, 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
*/
 
#ifndef SERVICE_LOCKING_INCLUDED
#define SERVICE_LOCKING_INCLUDED
 
/**
  @file include/mysql/service_locking.h
 
  Implements ::mysql_locking_service_st
*/
 
#ifndef MYSQL_ABI_CHECK
#include <stddef.h>
#include <stdint.h>
#endif /* MYSQL_ABI_CHECK */
 
#ifdef __cplusplus
class THD;
#define MYSQL_THD THD *
#else
#define MYSQL_THD void *
#endif
 
/**
  Types of locking service locks.
  LOCKING_SERVICE_READ is compatible with LOCKING_SERVICE_READ.
  All other combinations are incompatible.
*/
enum enum_locking_service_lock_type {
  LOCKING_SERVICE_READ,
  LOCKING_SERVICE_WRITE
};
 
/**
  Acquire locking service locks.
 
  @param opaque_thd      Thread handle. If NULL, current_thd will be used.
  @param lock_namespace  Namespace of the locks to acquire.
  @param lock_names      Array of names of the locks to acquire.
  @param lock_num        Number of elements in 'lock_names'.
  @param lock_type       Lock type to acquire. LOCKING_SERVICE_READ or _WRITE.
  @param lock_timeout    Number of seconds to wait before giving up.
 
  @retval 1              Acquisition failed, error has been reported.
  @retval 0              Acquisition successful, all locks acquired.
 
  @note both lock_namespace and lock_names are limited to 64 characters max.
  Names are compared using binary comparison.
 
  @sa acquire_locking_service_locks, MDL_context::acquire_locks
*/
typedef int (*mysql_acquire_locks_t)(
    MYSQL_THD opaque_thd, const char *lock_namespace, const char **lock_names,
    size_t lock_num, enum enum_locking_service_lock_type lock_type,
    uint64_t lock_timeout);
 
/**
  Release all lock service locks taken by the given connection
  in the given namespace.
 
  @param opaque_thd      Thread handle. If NULL, current_thd will be used.
  @param lock_namespace  Namespace of the locks to release.
 
  @retval 1              Release failed, error has been reported.
  @retval 0              Release successful, all locks acquired.
 
  @sa release_locking_service_locks, MDL_context::release_locks
*/
typedef int (*mysql_release_locks_t)(MYSQL_THD opaque_thd,
                                     const char *lock_namespace);
 
/**
  @ingroup group_ext_plugin_services
 
  This service provides support for taking read/write locks.
  It is intended for use with fabric, but it is still a general
  service. The locks are in a separate namespace from other
  locks in the server, and there is also no interactions with
  transactions (i.e. locks are not released on commit/abort).
 
  These locks are implemented using the metadata lock (MDL) subsystem
  and thus deadlocks involving locking service locks and other types
  of metadata will be detected using the MDL deadlock detector.
*/
extern "C" struct mysql_locking_service_st {
  mysql_acquire_locks_t mysql_acquire_locks;
  mysql_release_locks_t mysql_release_locks;
} *mysql_locking_service;
 
#ifdef MYSQL_DYNAMIC_PLUGIN
 
#define mysql_acquire_locking_service_locks(_THD, _NAMESPACE, _NAMES, _NUM,  \
                                            _TYPE, _TIMEOUT)                 \
  mysql_locking_service->mysql_acquire_locks(_THD, _NAMESPACE, _NAMES, _NUM, \
                                             _TYPE, _TIMEOUT)
#define mysql_release_locking_service_locks(_THD, _NAMESPACE) \
  mysql_locking_service->mysql_release_locks(_THD, _NAMESPACE)
 
#else
 
int mysql_acquire_locking_service_locks(
    MYSQL_THD opaque_thd, const char *lock_namespace, const char **lock_names,
    size_t lock_num, enum enum_locking_service_lock_type lock_type,
    uint64_t lock_timeout);
 
int mysql_release_locking_service_locks(MYSQL_THD opaque_thd,
                                        const char *lock_namespace);
 
#endif /* MYSQL_DYNAMIC_PLUGIN */
 
#endif /* SERVICE_LOCKING_INCLUDED */