diff options
Diffstat (limited to 'sql/mdl.h')
| -rw-r--r-- | sql/mdl.h | 136 |
1 files changed, 100 insertions, 36 deletions
diff --git a/sql/mdl.h b/sql/mdl.h index 8edbfbc0777..3ae7cdc743d 100644 --- a/sql/mdl.h +++ b/sql/mdl.h @@ -36,11 +36,13 @@ class MDL_ticket; (because of that their acquisition involves implicit acquisition of global intention-exclusive lock). - @see Comments for can_grant_lock() and can_grant_global_lock() for details. + @sa Comments for MDL_object_lock::can_grant_lock() and + MDL_global_lock::can_grant_lock() for details. */ enum enum_mdl_type {MDL_SHARED=0, MDL_SHARED_HIGH_PRIO, - MDL_SHARED_UPGRADABLE, MDL_EXCLUSIVE}; + MDL_SHARED_UPGRADABLE, MDL_INTENTION_EXCLUSIVE, + MDL_EXCLUSIVE}; /** States which a metadata lock ticket can have. */ @@ -78,7 +80,8 @@ public: enum enum_mdl_namespace { TABLE=0, FUNCTION, PROCEDURE, - TRIGGER }; + TRIGGER, + GLOBAL }; const uchar *ptr() const { return (uchar*) m_ptr; } uint length() const { return m_length; } @@ -93,7 +96,8 @@ public: { return (enum_mdl_namespace)(m_ptr[0]); } /** - Construct a metadata lock key from a triplet (mdl_namespace, database and name). + Construct a metadata lock key from a triplet (mdl_namespace, + database and name). @remark The key for a table is <mdl_namespace>+<database name>+<table name> @@ -102,11 +106,12 @@ public: @param name Name of of the object @param key Where to store the the MDL key. */ - void mdl_key_init(enum_mdl_namespace mdl_namespace, const char *db, const char *name) + void mdl_key_init(enum_mdl_namespace mdl_namespace, + const char *db, const char *name) { m_ptr[0]= (char) mdl_namespace; - m_db_name_length= (uint) (strmov(m_ptr + 1, db) - m_ptr - 1); - m_length= (uint) (strmov(m_ptr + m_db_name_length + 2, name) - m_ptr + 1); + m_db_name_length= (uint16) (strmov(m_ptr + 1, db) - m_ptr - 1); + m_length= (uint16) (strmov(m_ptr + m_db_name_length + 2, name) - m_ptr + 1); } void mdl_key_init(const MDL_key *rhs) { @@ -119,20 +124,34 @@ public: return (m_length == rhs->m_length && memcmp(m_ptr, rhs->m_ptr, m_length) == 0); } + /** + Compare two MDL keys lexicographically. + */ + int cmp(const MDL_key *rhs) const + { + /* + The key buffer is always '\0'-terminated. Since key + character set is utf-8, we can safely assume that no + character starts with a zero byte. + */ + return memcmp(m_ptr, rhs->m_ptr, min(m_length, rhs->m_length)+1); + } + MDL_key(const MDL_key *rhs) { mdl_key_init(rhs); } - MDL_key(enum_mdl_namespace namespace_arg, const char *db_arg, const char *name_arg) + MDL_key(enum_mdl_namespace namespace_arg, + const char *db_arg, const char *name_arg) { mdl_key_init(namespace_arg, db_arg, name_arg); } MDL_key() {} /* To use when part of MDL_request. */ private: + uint16 m_length; + uint16 m_db_name_length; char m_ptr[MAX_MDLKEY_LENGTH]; - uint m_length; - uint m_db_name_length; private: MDL_key(const MDL_key &); /* not implemented */ MDL_key &operator=(const MDL_key &); /* not implemented */ @@ -198,7 +217,7 @@ public: DBUG_ASSERT(ticket == NULL); type= type_arg; } - bool is_shared() const { return type < MDL_EXCLUSIVE; } + bool is_shared() const { return type < MDL_INTENTION_EXCLUSIVE; } static MDL_request *create(MDL_key::enum_mdl_namespace mdl_namespace, const char *db, const char *name, @@ -243,6 +262,17 @@ typedef void (*mdl_cached_object_release_hook)(void *); @note Multiple shared locks on a same object are represented by a single ticket. The same does not apply for other lock types. + + @note There are two groups of MDL_ticket members: + - "Externally accessible". These members can be accessed from + threads/contexts different than ticket owner in cases when + ticket participates in some list of granted or waiting tickets + for a lock. Therefore one should change these members before + including then to waiting/granted lists or while holding lock + protecting those lists. + - "Context private". Such members are private to thread/context + owning this ticket. I.e. they should not be accessed from other + threads/contexts. */ class MDL_ticket @@ -250,12 +280,13 @@ class MDL_ticket public: /** Pointers for participating in the list of lock requests for this context. + Context private. */ MDL_ticket *next_in_context; MDL_ticket **prev_in_context; /** Pointers for participating in the list of satisfied/pending requests - for the lock. + for the lock. Externally accessible. */ MDL_ticket *next_in_lock; MDL_ticket **prev_in_lock; @@ -265,8 +296,8 @@ public: void *get_cached_object(); void set_cached_object(void *cached_object, mdl_cached_object_release_hook release_hook); - const MDL_context *get_ctx() const { return m_ctx; } - bool is_shared() const { return m_type < MDL_EXCLUSIVE; } + MDL_context *get_ctx() const { return m_ctx; } + bool is_shared() const { return m_type < MDL_INTENTION_EXCLUSIVE; } bool is_upgradable_or_exclusive() const { return m_type == MDL_SHARED_UPGRADABLE || m_type == MDL_EXCLUSIVE; @@ -275,6 +306,8 @@ public: void downgrade_exclusive_lock(); private: friend class MDL_context; + friend class MDL_global_lock; + friend class MDL_object_lock; MDL_ticket(MDL_context *ctx_arg, enum_mdl_type type_arg) : m_type(type_arg), @@ -283,31 +316,31 @@ private: m_lock(NULL) {} - static MDL_ticket *create(MDL_context *ctx_arg, enum_mdl_type type_arg); static void destroy(MDL_ticket *ticket); private: - /** Type of metadata lock. */ + /** Type of metadata lock. Externally accessible. */ enum enum_mdl_type m_type; - /** State of the metadata lock ticket. */ + /** State of the metadata lock ticket. Context private. */ enum enum_mdl_state m_state; - /** Context of the owner of the metadata lock ticket. */ + /** + Context of the owner of the metadata lock ticket. Externally accessible. + */ MDL_context *m_ctx; - /** Pointer to the lock object for this lock ticket. */ + /** Pointer to the lock object for this lock ticket. Context private. */ MDL_lock *m_lock; private: MDL_ticket(const MDL_ticket &); /* not implemented */ MDL_ticket &operator=(const MDL_ticket &); /* not implemented */ - - bool has_pending_conflicting_lock_impl() const; }; typedef I_P_List<MDL_request, I_P_List_adapter<MDL_request, &MDL_request::next_in_list, - &MDL_request::prev_in_list> > + &MDL_request::prev_in_list>, + I_P_List_counter> MDL_request_list; /** @@ -326,21 +359,19 @@ public: typedef Ticket_list::Iterator Ticket_iterator; - void init(THD *thd); + MDL_context(); void destroy(); bool try_acquire_shared_lock(MDL_request *mdl_request); bool acquire_exclusive_lock(MDL_request *mdl_request); bool acquire_exclusive_locks(MDL_request_list *requests); bool try_acquire_exclusive_lock(MDL_request *mdl_request); - bool acquire_global_shared_lock(); bool clone_ticket(MDL_request *mdl_request); bool wait_for_locks(MDL_request_list *requests); void release_all_locks_for_name(MDL_ticket *ticket); void release_lock(MDL_ticket *ticket); - void release_global_shared_lock(); bool is_exclusive_lock_owner(MDL_key::enum_mdl_namespace mdl_namespace, const char *db, @@ -368,7 +399,6 @@ public: void set_lt_or_ha_sentinel() { - DBUG_ASSERT(m_lt_or_ha_sentinel == NULL); m_lt_or_ha_sentinel= mdl_savepoint(); } MDL_ticket *lt_or_ha_sentinel() const { return m_lt_or_ha_sentinel; } @@ -385,16 +415,35 @@ public: bool can_wait_lead_to_deadlock() const; inline THD *get_thd() const { return m_thd; } - - bool is_waiting_in_mdl() const { return m_is_waiting_in_mdl; } -private: - Ticket_list m_tickets; - bool m_has_global_shared_lock; + /** - Indicates that the owner of this context is waiting in - wait_for_locks() method. + Wake up context which is waiting for a change of MDL_lock state. */ - bool m_is_waiting_in_mdl; + void awake() + { + pthread_cond_signal(&m_ctx_wakeup_cond); + } + + bool try_acquire_global_intention_exclusive_lock(MDL_request *mdl_request); + bool acquire_global_intention_exclusive_lock(MDL_request *mdl_request); + + bool acquire_global_shared_lock(); + void release_global_shared_lock(); + + /** + Check if this context owns global lock of particular type. + */ + bool is_global_lock_owner(enum_mdl_type type_arg) + { + MDL_request mdl_request; + bool not_used; + mdl_request.init(MDL_key::GLOBAL, "", "", type_arg); + return find_ticket(&mdl_request, ¬_used); + } + + void init(THD *thd_arg) { m_thd= thd_arg; } +private: + Ticket_list m_tickets; /** This member has two uses: 1) When entering LOCK TABLES mode, remember the last taken @@ -406,12 +455,27 @@ private: */ MDL_ticket *m_lt_or_ha_sentinel; THD *m_thd; + /** + Condvar which is used for waiting until this context's pending + request can be satisfied or this thread has to perform actions + to resolve potential deadlock (we subscribe for such notification + by adding ticket corresponding to the request to an appropriate + queue of waiters). + */ + pthread_cond_t m_ctx_wakeup_cond; private: - void release_ticket(MDL_ticket *ticket); - bool can_wait_lead_to_deadlock_impl() const; MDL_ticket *find_ticket(MDL_request *mdl_req, bool *is_lt_or_ha); void release_locks_stored_before(MDL_ticket *sentinel); + + bool try_acquire_lock_impl(MDL_request *mdl_request); + bool acquire_lock_impl(MDL_request *mdl_request); + bool acquire_exclusive_lock_impl(MDL_request *mdl_request); + + friend bool MDL_ticket::upgrade_shared_lock_to_exclusive(); +private: + MDL_context(const MDL_context &rhs); /* not implemented */ + MDL_context &operator=(MDL_context &rhs); /* not implemented */ }; |