- 01 Feb, 2010 3 commits
-
-
Dmitry Lenev authored
caused by patch which implemented new type-of-operation-aware metadata locks and added a wait-for graph based deadlock detector to the MDL subsystem (this patch fixed bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table"). Crashes were caused by a race in MDL_context::try_acquire_lock(). This method added MDL_ticket to the list of granted tickets and released lock protecting list before setting MDL_ticket::m_lock. Thus some other thread was able to see ticket without properly set m_lock member for some short period of time. If this thread called method involving this member during this period crash happened. This fix ensures that MDL_ticket::m_lock is set in all cases when ticket is added to granted/pending lists in MDL_lock. sql/mdl.cc: We must set MDL_ticket::m_lock member before adding ticket to the list of granted tickets, since such tickets can be accessed by other threads which might call methods using this member. Added assert which ensures that all MDL_tickets which are added to the granted/pending lists have properly set MDL_ticket::m_lock member. sql/mdl.h: Adjusted comment describing MDL_ticket::m_lock member to reflect current reality. Added accessor method for this member.
-
Konstantin Osipov authored
in a pointer arithmetics expression).
-
Dmitry Lenev authored
Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list. mysql-test/include/handler.inc: Adjusted test case to trigger an execution path on which bug 41110 "crash with handler command when used concurrently with alter table" and bug 41112 "crash in mysql_ha_close_table/get_lock_data with alter table" were originally discovered. Left old test case which no longer triggers this execution path for the sake of coverage. Added test coverage for HANDLER SQL statements and type-aware metadata locks. Added a test for the global shared lock and HANDLER SQL. Updated tests to take into account that the old simple deadlock detection heuristics was replaced with a graph-based deadlock detector. mysql-test/r/debug_sync.result: Updated results (see debug_sync.test). mysql-test/r/handler_innodb.result: Updated results (see handler.inc test). mysql-test/r/handler_myisam.result: Updated results (see handler.inc test). mysql-test/r/innodb-lock.result: Updated results (see innodb-lock.test). mysql-test/r/innodb_mysql_lock.result: Updated results (see innodb_mysql_lock.test). mysql-test/r/lock.result: Updated results (see lock.test). mysql-test/r/lock_multi.result: Updated results (see lock_multi.test). mysql-test/r/lock_sync.result: Updated results (see lock_sync.test). mysql-test/r/mdl_sync.result: Updated results (see mdl_sync.test). mysql-test/r/sp-threads.result: SHOW PROCESSLIST output has changed due to the fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/r/truncate_coverage.result: Updated results (see truncate_coverage.test). mysql-test/suite/funcs_1/datadict/processlist_val.inc: SELECT FROM I_S.PROCESSLIST output has changed due to fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/suite/funcs_1/r/processlist_val_no_prot.result: SELECT FROM I_S.PROCESSLIST output has changed due to fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/suite/rpl/t/rpl_sp.test: Updated to a new SHOW PROCESSLIST state name. mysql-test/t/debug_sync.test: Use LOCK TABLES READ instead of LOCK TABLES WRITE as the latter no longer allows to trigger execution path involving waiting on thr_lock.c lock and therefore reaching debug sync-point covered by this test. mysql-test/t/innodb-lock.test: Adjusted test case to the fact that innodb_table_locks=0 option is no longer supported, since LOCK TABLES WRITE handles all its conflicts within MDL subsystem. mysql-test/t/innodb_mysql_lock.test: Added test for bug #37346 "innodb does not detect deadlock between update and alter table". mysql-test/t/lock.test: Added test coverage which checks the fact that we no longer support DDL under LOCK TABLES on tables which were locked implicitly. Adjusted existing test cases accordingly. mysql-test/t/lock_multi.test: Added test for bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock". Adjusted other test cases to take into account the fact that waiting for LOCK TABLES ... WRITE now happens within MDL subsystem. mysql-test/t/lock_sync.test: Since LOCK TABLES ... WRITE now takes SNRW metadata lock for tables locked explicitly we have to implicitly lock InnoDB tables (through view) to trigger the table-level lock conflict between TL_WRITE and TL_WRITE_ALLOW_WRITE. mysql-test/t/mdl_sync.test: Added basic test coverage for type-of-operation-aware metadata locks. Also covered with tests some use cases involving HANDLER statements in which a deadlock could arise. Adjusted existing tests to take type-of-operation-aware MDL into account. mysql-test/t/multi_update.test: Update to a new SHOW PROCESSLIST state name. mysql-test/t/truncate_coverage.test: Adjusted test case after making LOCK TABLES WRITE to wait until transactions that use the table to be locked are completed. Updated to the changed name of DEBUG_SYNC point. sql/handler.cc: Global read lock functionality has been moved into a class. sql/lock.cc: Global read lock functionality has been moved into a class. Updated code to use the new MDL API. sql/mdl.cc: Introduced new type-of-operation aware metadata locks. To do this: - Changed MDL_lock to use one list for waiting requests and one list for granted requests. For each list, added a bitmap that holds information what lock types a list contains. Added a helper class MDL_lock::List to manipulate with granted and waited lists while keeping the bitmaps in sync with list contents. - Changed lock-compatibility functions to use bitmaps that define compatibility. - Introduced a graph based deadlock detector inspired by waiting_threads.c from Maria implementation. - Now that we have a deadlock detector, and no longer have a global lock to protect individual lock objects, but rather use an rw lock per object, removed redundant code for upgrade, and the global read lock. Changed the MDL API to no longer require the caller to acquire the global intention exclusive lock by means of a separate method. Removed a few more methods that became redundant. - Removed deadlock detection heuristic, it has been made obsolete by the deadlock detector. - With operation-type-aware metadata locks, MDL subsystem has become aware of potential conflicts between DDL and open transactions. This made it possible to remove calls to mysql_abort_transactions_with_shared_lock() from acquisition paths for exclusive lock and lock upgrade. Now we can simply wait for these transactions to complete without fear of deadlock. Function mysql_lock_abort() has also become unnecessary for all conflicting cases except when a DDL conflicts with a connection that has an open HANDLER. sql/mdl.h: Introduced new type-of-operation aware metadata locks. Introduced a graph based deadlock detector and supporting methods. Added comments. God rid of redundant API calls. Renamed m_lt_or_ha_sentinel to m_trans_sentinel, since now it guards the global read lock as well as LOCK TABLES and HANDLER locks. sql/mysql_priv.h: Moved the global read lock functionality into a class. Added MYSQL_OPEN_FORCE_SHARED_MDL flag which forces open_tables() to take MDL_SHARED on tables instead of metadata locks specified in the parser. We use this to allow PREPARE run concurrently in presence of LOCK TABLES ... WRITE. Added signature for find_table_for_mdl_ugprade(). sql/set_var.cc: Global read lock functionality has been moved into a class. sql/sp_head.cc: When creating TABLE_LIST elements for prelocking or system tables set the type of request for metadata lock according to the operation that will be performed on the table. sql/sql_base.cc: - Updated code to use the new MDL API. - In order to avoid locks starvation we take upgradable locks all at once. As result implicitly locked tables no longer get an upgradable lock. Consequently DDL and FLUSH TABLES for such tables is prohibited. find_write_locked_table() was replaced by find_table_for_mdl_upgrade() function. open_table() was adjusted to return TABLE instance with upgradable ticket when necessary. - We no longer wait for all locks on OT_WAIT back off action -- only on the lock that caused the wait conflict. Moreover, now we distinguish cases when we have to wait due to conflict in MDL and old version of table in TDC. - Upate mysql_notify_threads_having_share_locks() to only abort thr_lock.c waits of threads that have open HANDLERs, since lock conflicts with only these threads now can lead to deadlocks not detectable by the MDL deadlock detector. - Remove mysql_abort_transactions_with_shared_locks() which is no longer needed. sql/sql_class.cc: Global read lock functionality has been moved into a class. Re-arranged code in THD::cleanup() to simplify assert. sql/sql_class.h: Introduced class to incapsulate global read lock functionality. Now sentinel in MDL subsystem guards the global read lock as well as LOCK TABLES and HANDLER locks. Adjusted code accordingly. sql/sql_db.cc: Global read lock functionality has been moved into a class. sql/sql_delete.cc: We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result TRUNCATE TABLE is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_handler.cc: Inform MDL_context about presence of open HANDLERs. Since HANLDERs break MDL protocol by acquiring table-level lock while holding only S metadata lock on a table MDL subsystem should take special care about such contexts (Now this is the only case when mysql_lock_abort() is used). sql/sql_parse.cc: Global read lock functionality has been moved into a class. Do not take upgradable metadata locks when opening tables for CREATE TABLE SELECT as it is not necessary and limits concurrency. When initializing TABLE_LIST objects before adding them to the table list set the type of request for metadata lock according to the operation that will be performed on the table. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result FLUSH TABLES is no longer allowed for such tables. sql/sql_prepare.cc: Use MYSQL_OPEN_FORCE_SHARED_MDL flag when opening tables during PREPARE. This allows PREPARE to run concurrently in presence of LOCK TABLES ... WRITE. sql/sql_rename.cc: Global read lock functionality has been moved into a class. sql/sql_show.cc: Updated code to use the new MDL API. sql/sql_table.cc: Global read lock functionality has been moved into a class. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result DROP TABLE is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_trigger.cc: Global read lock functionality has been moved into a class. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result CREATE/DROP TRIGGER is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_view.cc: Global read lock functionality has been moved into a class. Fixed results of wrong merge that led to misuse of GLR API. CREATE VIEW statement is not a commit statement. sql/table.cc: When resetting TABLE_LIST objects for PS or SP re-execution set the type of request for metadata lock according to the operation that will be performed on the table. Do the same in auxiliary function initializing metadata lock requests in a table list. sql/table.h: When initializing TABLE_LIST objects set the type of request for metadata lock according to the operation that will be performed on the table. sql/transaction.cc: Global read lock functionality has been moved into a class.
-
- 21 Jan, 2010 1 commit
-
-
Dmitry Lenev authored
condition variable per context instead of one mutex and one conditional variable for the whole subsystem. This should increase concurrency in this subsystem. It also opens the way for further changes which are necessary to solve such bugs as bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". Two other notable changes done by this patch: - MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. - Instead of using separate MDL_context for opening system tables/tables for purposes of I_S we now create MDL savepoint in the main context before opening tables and rollback to this savepoint after closing them. This means that it is now possible to get ER_LOCK_DEADLOCK error even not inside a transaction. This might happen in unlikely case when one runs DDL on one of system tables while also running DDL on some other tables. Cases when this ER_LOCK_DEADLOCK error is not justified will be addressed by advanced deadlock detector for MDL subsystem which we plan to implement. mysql-test/include/handler.inc: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/handler_innodb.result: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/handler_myisam.result: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/mdl_sync.result: Adjusted mdl_sync.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/t/mdl_sync.test: Adjusted mdl_sync.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. sql/events.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/ha_ndbcluster.cc: Since manipulations with open table state no longer install proxy MDL_context it does not make sense to perform them in order to satisfy assert in mysql_rm_tables_part2(). Removed them per agreement with Cluster team. This has not broken test suite since scenario in which deadlock can occur and assertion fails is not covered by tests. sql/lock.cc: MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/log.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/mdl.cc: Changed metadata locking subsystem to use mutex per lock and condition variable per context instead of one mutex and one conditional variable for the whole subsystem. Changed approach to handling of global metadata locks. Instead of implicitly acquiring intention exclusive locks when user requests per-object upgradeable or exclusive locks now we require them to be acquired explicitly in the same way as ordinary metadata locks. In fact global lock are now ordinary metadata locks in new GLOBAL namespace. To implement these changes: - Removed LOCK_mdl mutex and COND_mdl condition variable. - Introduced MDL_lock::m_mutex mutexes which protect individual lock objects. - Replaced mdl_locks hash with MDL_map class, which has hash for MDL_lock objects as a member and separate mutex which protects this hash. Methods of this class allow to find(), find_or_create() or remove() MDL_lock objects in concurrency-friendly fashion (i.e. for most common operation, find_or_create(), we don't acquire MDL_lock::m_mutex while holding MDL_map::m_mutex. Thanks to MikaelR for this idea and benchmarks!). Added three auxiliary members to MDL_lock class (m_is_destroyed, m_ref_usage, m_ref_release) to support this concurrency-friendly behavior. - Introduced MDL_context::m_ctx_wakeup_cond condition variable to be used for waiting until this context's pending request can be satisfied or its thread has to perform actions to resolve potential deadlock. Context which want to wait add ticket corresponding to the request to an appropriate queue of waiters in MDL_lock object so they can be noticed when other contexts change state of lock and be awaken by them by signalling on MDL_context::m_ctx_wakeup_cond. As consequence MDL_ticket objects has to be used for any waiting in metadata locking subsystem including one which happens in MDL_context::wait_for_locks() method. Another consequence is that MDL_context is no longer copyable and can't be saved/restored when working with system tables. - Made MDL_lock an abstract class, which delegates specifying exact compatibility matrix to its descendants. Added MDL_global_lock child class for global lock (The old is_lock_type_compatible() method became can_grant_lock() method of this class). Added MDL_object_lock class to represent per-object lock (The old MDL_lock::can_grant_lock() became its method). Choice between two classes happens based on MDL namespace in MDL_lock::create() method. - Got rid of MDL_lock::type member as its meaning became ambigous for global locks. - To simplify waking up of contexts waiting for lock split waiting queue in MDL_lock class in two queues. One for pending requests for exclusive (including intention exclusive) locks and another for requests for shared locks. - Added virtual wake_up_waiters() method to MDL_lock, MDL_global_lock and MDL_object_lock classes which allows to wake up waiting contexts after state of lock changes. Replaced old duplicated code with calls to this method. - Adjusted MDL_context::try_acquire_shared_lock()/exclusive_lock()/ global_shared_lock(), MDL_ticket::upgrade_shared_lock_to_exclusive_lock() and MDL_context::release_ticket() methods to use MDL_map and MDL_lock::m_mutex instead of single LOCK_mdl mutex and wake up waiters according to the approach described above. The latter method also was renamed to MDL_context::release_lock(). - Changed MDL_context::try_acquire_shared_lock()/exclusive_lock() and release_lock() not to handle global locks. They are now supposed to be taken explicitly like ordinary metadata locks. - Added helper MDL_context::try_acquire_global_intention_exclusive_lock() and acquire_global_intention_exclusive_lock() methods. - Moved common code from MDL_context::acquire_global_shared_lock() and acquire_global_intention_exclusive_lock() to new method - MDL_context::acquire_lock_impl(). - Moved common code from MDL_context::try_acquire_shared_lock(), try_acquire_global_intention_exclusive_lock()/exclusive_lock() to MDL_context::try_acquire_lock_impl(). - Since acquiring of several exclusive locks can no longer happen under single LOCK_mdl mutex the approach to it had to be changed. Now we do it in one by one fashion. This is done in alphabetical order to avoid deadlocks. Changed MDL_context::acquire_exclusive_locks() accordingly (as part of this change moved code responsible for acquiring single exclusive lock to new MDL_context::acquire_exclusive_lock_impl() method). - Since we no longer have single LOCK_mdl mutex which protects all MDL_context::m_is_waiting_in_mdl members using these members to determine if we have really awaken context holding conflicting shared lock became inconvinient. Got rid of this member and changed notify_shared_lock() helper function and process of acquiring of/upgrading to exclusive lock not to rely on such information. Now in MDL_context::acquire_exclusive_lock_impl() and MDL_ticket::upgrade_shared_lock_to_exclusive_lock() we simply re-try to wake up threads holding conflicting shared locks after small time out. - Adjusted MDL_context::can_wait_lead_to_deadlock() and MDL_ticket::has_pending_conflicting_lock() to use per-lock mutexes instead of LOCK_mdl. To do this introduced MDL_lock::has_pending_exclusive_lock() method. sql/mdl.h: Changed metadata locking subsystem to use mutex per lock and condition variable per context instead of one mutex and one conditional variable for the whole subsystem. In order to implement this change: - Added MDL_key::cmp() method to be able to sort MDL_key objects alphabetically. Changed length fields in MDL_key class to uint16 as 16-bit is enough for length of any key. - Changed MDL_ticket::get_ctx() to return pointer to non-const object in order to be able to use MDL_context::awake() method for such contexts. - Got rid of unlocked versions of can_wait_lead_to_deadlock()/ has_pending_conflicting_lock() methods in MDL_context and MDL_ticket. We no longer has single mutex which protects all locks. Thus one always has to use versions of these methods which acquire per-lock mutexes. - MDL_request_list type of list now counts its elements. - Added MDL_context::m_ctx_wakeup_cond condition variable to be used for waiting until this context's pending request can be satisfied or its thread has to perform actions to resolve potential deadlock. Added awake() method to wake up context from such wait. Addition of condition variable made MDL_context uncopyable. As result we no longer can save/restore MDL_context when working with system tables. Instead we create MDL savepoint before opening those tables and rollback to it once they are closed. - MDL_context::release_ticket() became release_lock() method. - Added auxiliary MDL_context::acquire_exclusive_lock_impl() method which does all necessary work to acquire exclusive lock on one object but should not be used directly as it does not enforce any asserts ensuring that no deadlocks are possible. - Since we no longer need to know if thread trying to acquire exclusive lock managed to wake up any threads having conflicting shared locks (as, anyway, we will try to wake up such threads again shortly) - MDL_context::m_is_waiting_in_mdl member became unnecessary and notify_shared_lock() no longer needs to be friend of MDL_context. Changed approach to handling of global metadata locks. Instead of implicitly acquiring intention exclusive locks when user requests per-object upgradeable or exclusive locks now we require them to be acquired explicitly in the same way as ordinary metadata locks. - Added new GLOBAL namespace for such locks. - Added new type of lock to be requested MDL_INTENTION_EXCLISIVE. - Added MDL_context::try_acquire_global_intention_exclusive_lock() and acquire_global_intention_exclusive_lock() methods. - Moved common code from MDL_context::acquire_global_shared_lock() and acquire_global_intention_exclusive_lock() to new method - MDL_context::acquire_lock_impl(). - Moved common code from MDL_context::try_acquire_shared_lock(), try_acquire_global_intention_exclusive_lock()/exclusive_lock() to MDL_context::try_acquire_lock_impl(). - Added helper MDL_context::is_global_lock_owner() method to be able easily to find what kind of global lock this context holds. - MDL_context::m_has_global_shared_lock became unnecessary as global read lock is now represented by ordinary ticket. - Removed assert in MDL_context::set_lt_or_ha_sentinel() which became false for cases when we execute LOCK TABLES under global read lock mode. sql/mysql_priv.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result calls opening/closing system tables were changed to use Open_tables_backup instead of Open_table_state class as well. sql/sp.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sp.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_base.cc: close_thread_tables(): Since we no longer use separate MDL_context for opening system tables we need to avoid releasing all transaction locks when closing system table. Releasing metadata lock on system table is now responsibility of THD::restore_backup_open_tables_state(). open_table_get_mdl_lock(), Open_table_context::recover_from_failed_open(): MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object upgradable or exclusive metadata lock is acquired. So this have to be done explicitly from these calls. Changed Open_table_context class to store MDL_request object for global intention exclusive lock acquired when opening tables. open_table(): Do not release metadata lock if we have failed to open table as this lock might have been acquired by one of previous statements in transaction, and therefore should not be released. open_system_tables_for_read()/close_system_tables()/ open_performance_schema_table(): Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. close_performance_schema_table(): Got rid of duplicated code. sql/sql_class.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. Also releasing metadata lock on system table is now responsibility of THD::restore_backup_open_tables_state(). Adjusted assert in THD::cleanup() to take into account fact that now we also use MDL sentinel for global read lock. sql/sql_class.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. As result: - 'mdl_context' member was moved out of Open_tables_state to THD class. enter_locked_tables_mode()/leave_locked_tables_mode() had to follow. - Methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. Changed Open_table_context class to store MDL_request object for global intention exclusive lock acquired when opening tables. sql/sql_delete.cc: MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/sql_help.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_parse.cc: Adjusted assert reload_acl_and_cache() to the fact that global read lock now takes full-blown metadata lock. sql/sql_plist.h: Added support for element counting to I_P_List list template. One can use policy classes to specify if such counting is needed or not needed for particular list. sql/sql_show.cc: Instead of using separate MDL_context for opening tables for I_S purposes we now create MDL savepoint in the main context before opening tables and rollback to this savepoint after closing them. To support this and similar change for system tables methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing tables for I_S purposes was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_table.cc: mysql_rm_tables_part2(): Since now global intention exclusive metadata lock is ordinary metadata lock we no longer can rely that by releasing MDL locks on all tables we will release all locks acquired by this routine. So in non-LOCK-TABLES mode we have to release all locks acquired explicitly. prepare_for_repair(), mysql_alter_table(): MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/tztime.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. Also changed code not to use special mechanism for open system tables when it is not really necessary.
-
- 20 Jan, 2010 1 commit
-
-
Jon Olav Hauglid authored
Diagnostics_area::set_ok_status at PREPARE The problem occured during processing of stored routines. Routines are loaded from mysql.proc, parsed and put into the sp cache by sp_cache_routine(). The assert occured because the return value from sp_cache_routine() was not checked for top level CALLs. This meant that any errors during sp_cache_routine() went unoticed and triggered the assert when my_ok() was later called. This is a regression introduced by the patch for Bug#30977, only visible in source trees with MDL and using debug builds of the server. This patch fixes the problem by checking the return value from sp_cache_routine() for top level CALLs and propagating any errors similar to what is done for other calls to sp_cache_routine(). No test case added.
-
- 15 Jan, 2010 1 commit
-
-
Jon Olav Hauglid authored
The problem was that FLUSH TABLE <table_list> would block, waiting for all tables with old versions to be removed from the table definition cache, rather than waiting for only the tables in <table_list>. This could happen if FLUSH TABLE was used in combination with LOCK TABLES. With the new MDL code, this problem is no longer repeatable. Regression test case added to lock.test. This commit contains no code changes.
-
- 14 Jan, 2010 1 commit
-
-
Jon Olav Hauglid authored
revno: 2762 [merge] committer: Matthias Leich <mleich@mysql.com> branch nick: mysql-6.0-bugteam-push timestamp: Wed 2008-08-13 22:05:34 +0200 message: Upmerge 5.1 -> 6.0 ------------------------------------------------------------ revno: 2497.374.2 committer: Matthias Leich <mleich@mysql.com> branch nick: mysql-5.1-bugteam-push timestamp: Wed 2008-08-13 21:44:54 +0200 message: Fix for Bug#37853 Test "funcs_1.processlist_val_ps" fails in various ways + corrections of logic in poll routines + minor improvements
-
- 12 Jan, 2010 2 commits
-
-
Jon Olav Hauglid authored
This was a deadlock between LOCK TABLES/CREATE DATABASE in one connection and DROP DATABASE in another. It only happened if the table locked by LOCK TABLES was in the database to be dropped. The deadlock is similar to the one in Bug#48940, but with LOCK TABLES instead of an active transaction. The order of events needed to trigger the deadlock was: 1) Connection 1 locks table db1.t1 using LOCK TABLES. It will now have a metadata lock on the table name. 2) Connection 2 issues DROP DATABASE db1. This will wait inside the MDL subsystem for the lock on db1.t1 to go away. While waiting, it will hold the LOCK_mysql_create_db mutex. 3) Connection 1 issues CREATE DATABASE (database name irrelevant). This will hang trying to lock the same mutex. Since this is the connection holding the metadata lock blocking Connection 2, we have a deadlock. This deadlock would also happen for earlier trees without MDL, but there DROP DATABASE would wait for a table to be removed from the table definition cache. This patch fixes the problem by prohibiting CREATE DATABASE in LOCK TABLES mode. In the example above, this prevents Connection 1 from hanging trying to get the LOCK_mysql_create_db mutex. Note that other commands that use LOCK_mysql_create_db (ALTER/DROP DATABASE) are already prohibited in LOCK TABLES mode. Incompatible change: CREATE DATABASE is now disallowed in LOCK TABLES mode. Test case added to schema.test. mysql-test/t/drop.test: Updates the test for Bug#21216 by swapping the order of CREATE DATABASE and LOCK TABLES. This is now needed as CREATE DATABASE is prohibited in LOCK TABLES mode. mysql-test/t/schema.test: Test case for Bug#49988 added. Also fixes a problem with the test for Bug#48940 where the result would differ for embedded server.
-
Tor Didriksen authored
Bug#45523 "Objects of class base_ilist should not be copyable". Suppress the compiler-generated public copy constructor and assignment operator of class base_ilist; instead, implement move_elements_to() function which transfers ownership of elements from one list to another.
-
- 08 Jan, 2010 1 commit
-
-
Jon Olav Hauglid authored
INFILE". Attempts to execute an INSERT statement for a MEMORY table which invoked a trigger or called a stored function which tried to perform LOW_PRIORITY update on the table being inserted into, resulted in debug servers aborting due to an assertion failure. On non-debug servers such INSERTs failed with "Can't update table t1 in stored function/trigger because it is already used by statement which invoked this stored function/trigger" as expected. The problem was that in the above scenario TL_WRITE_CONCURRENT_INSERT is converted to TL_WRITE inside the thr_lock() function since the MEMORY engine does not support concurrent inserts. This triggered an assertion which assumed that for the same table, one thread always requests locks with higher thr_lock_type value first. When TL_WRITE_CONCURRENT_INSERT is upgraded to TL_WRITE after the locks have been sorted, this is no longer true. In this case, TL_WRITE was requested after acquiring a TL_WRITE_LOW_PRIORITY lock on the table, triggering the assert. This fix solves the problem by adjusting this assert to take this scenario into account. An alternative approach to change handler::store_locks() methods for all engines which do not support concurrent inserts in such way that TL_WRITE_CONCURRENT_INSERT is upgraded to TL_WRITE there instead, was considered too intrusive. Commit on behalf of Dmitry Lenev. mysql-test/r/lock.result: Added simplified test for bug #48538 "Assertion in thr_lock() on LOAD DATA CONCURRENT INFILE". mysql-test/t/lock.test: Added simplified test for bug #48538 "Assertion in thr_lock() on LOAD DATA CONCURRENT INFILE". mysys/thr_lock.c: Adjusted assertion to account for situation when TL_WRITE_CONCURRENT_INSERT is converted to TL_WRITE inside of the thr_lock() function because the engine of the table being locked does not support concurrent inserts. This scenario breaks assumption that for the same table one thread always requests locks with higher thr_lock_type value first, since TL_WRITE on the table (converted from TL_WRITE_CONCURRENT_INSERT) can be requested after acquiring a TL_WRITE_LOW_PRIORITY lock on the table. Note that it is still safe to grant a new lock without extra checks and waiting in such situation since TL_WRITE has the same compatibility rules as TL_WRITE_LOW_PRIORITY (their only difference is priority).
-
- 30 Dec, 2009 1 commit
-
-
Dmitry Lenev authored
This change is supposed to reduce number of ER_LOCK_DEADLOCK errors which occur when multi-statement transaction encounters conflicting metadata lock in cases when waiting is possible. The idea is not to fail ER_LOCK_DEADLOCK error immediately when we encounter conflicting metadata lock. Instead we release all metadata locks acquired by current statement and start to wait until conflicting lock go away. To avoid deadlocks we use simple empiric which aborts waiting with ER_LOCK_DEADLOCK error if it turns out that somebody is waiting for metadata locks owned by this transaction. This patch also fixes bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". The bug was that concurrent execution of UPDATE or MULTI-UPDATE statement as a part of multi-statement transaction that already has used table being updated and ALTER TABLE statement might have resulted of loss of isolation between this transaction and ALTER TABLE statement, which manifested itself as changes performed by ALTER TABLE becoming visible in transaction and wrong binary log order as a consequence. This problem occurred when UPDATE or MULTI-UPDATE's wait in mysql_lock_tables() call was aborted due to metadata lock upgrade performed by concurrent ALTER TABLE. After such abort all metadata locks held by transaction were released but transaction silently continued to be executed as if nothing has happened. We solve this problem by changing our code not to release all locks in such case. Instead we release only locks which were acquired by current statement and then try to reacquire them by restarting open/lock tables process. We piggyback on simple deadlock detector implementation since this change has to be done anyway for it. mysql-test/include/handler.inc: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/handler_innodb.result: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/handler_myisam.result: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/mdl_sync.result: Added test coverage for basic deadlock detection in metadata locking subsystem and for bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". mysql-test/r/sp-lock.result: Adjusted test coverage for metadata locking for stored routines since after introduction of basic deadlock detector for metadata locks number of scenarios in which ER_LOCK_DEADLOCK error in absence of deadlock has decreased. mysql-test/t/mdl_sync.test: Added test coverage for basic deadlock detection in metadata locking subsystem and for bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". mysql-test/t/sp-lock.test: Adjusted test coverage for metadata locking for stored routines since after introduction of basic deadlock detector for metadata locks number of scenarios in which ER_LOCK_DEADLOCK error in absence of deadlock has decreased. sql/log_event_old.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/mdl.cc: Changed metadata locking subsystem to support basic deadlock detection with a help of the following simple empiric -- we assume that there is a deadlock if there is a connection which has to wait for a metadata lock which is currently acquired by some connection which is itself waiting to be able to acquire some shared metadata lock. To implement this change: - Added MDL_context::can_wait_lead_to_deadlock()/_impl() methods which allow to find out if there is someone waiting for metadata lock which is held by the connection and therefore deadlocks are possible if this connection is going to wait for some metadata lock. To do this added version of MDL_ticket::has_pending_conflicting_lock() method which assumes that its caller already owns LOCK_mdl mutex. - Changed MDL_context::wait_for_locks() to use one of the above methods to check if somebody is waiting for metadata lock owned by this context (and therefore deadlock is possible) and emit ER_LOCK_DEADLOCK error in this case. Also now we mark context of connections waiting inside of this method by setting MDL_context::m_is_waiting_in_mdl member. Thanks to this such connection could be waken up if some other connection starts waiting for one of its metadata locks and so a deadlock can occur. - Adjusted notify_shared_lock() to wake up connections which wait inside MDL_context::wait_for_locks() while holding shared metadata lock. - Changed MDL_ticket::upgrade_shared_lock_to_exclusive() to add temporary ticket for exclusive lock to MDL_lock::waiting queue, so request for metadata lock upgrade can be properly detected by our empiric. Also now this method invokes a callback which forces transactions holding shared metadata lock on the table to call MDL_context:: can_wait_lead_to_deadlock() method even if they don't need any new metadata locks. Thanks to this such transactions can detect deadlocks/ livelocks between MDL and table-level locks. Also reduced timeouts between calls to notify_shared_lock() in MDL_ticket::upgrade_shared_lock_to_exclusive() and MDL_context::acquire_exclusive_locks(). This was necessary to get rid of call to mysql_lock_abort() in wait_while_table_is_used(). (Now we instead rely on notify_shared_lock() timely calling mysql_lock_abort_for_thread() for the table on which lock is being upgraded/acquired). sql/mdl.h: - Added a version of MDL_ticket::has_pending_conflicting_lock() method to be used in situations when caller already has acquired LOCK_mdl mutex. - Added MDL_context::can_wait_lead_to_deadlock()/_impl() methods which allow to find out if there is someone waiting for metadata lock which is held by this connection and thus deadlocks are possible if this connections will start waiting for some metadata lock. - Added MDL_context::m_is_waiting_in_mdl member to mark connections waiting in MDL_context::wait_for_locks() method of metadata locking subsystem. Added getter method for this private member to make it accessible in notify_shared_lock() auxiliary so we can wake-up such connections if they hold shared metadata locks. - Finally, added mysql_abort_transactions_with_shared_lock() callback to be able force transactions which don't need any new metadata locks still call MDL_context::can_wait_lead_to_deadlock() and detect some of deadlocks between metadata locks and table-level locks. sql/mysql_priv.h: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_base.cc: Changed approach to metadata locking for multi-statement transactions. We no longer fail ER_LOCK_DEADLOCK error immediately when we encounter conflicting metadata lock. Instead we release all metadata locks acquired by current statement and start to wait until conflicting locks to go away by calling MDL_context::wait_for_locks() method. To avoid deadlocks the latter implements simple empiric which aborts waiting with ER_LOCK_DEADLOCK error if it turns out that somebody is waiting for metadata locks owned by this transaction. To implement the change described above: - Introduced Open_table_context::m_start_of_statement_svp member to store state of metadata locks at the start of the statement. - Changed Open_table_context::request_backoff_action() not to fail with ER_LOCK_DEADLOCK immediately if back-off is requested due to conflicting metadata lock. - Added new argument for close_tables_for_reopen() procedure which allows to specify subset of metadata locks to be released. - Changed open_tables() not to release all metadata locks acquired by current transaction when metadata lock conflict is discovered. Instead we release only locks acquired by current statement. - Changed open_ltable() and open_and_lock_tables_derived() not to emit ER_LOCK_DEADLOCK error when mysql_lock_tables() is aborted in multi-statement transaction when somebody tries to acquire exclusive metadata lock on the table. Instead we release metadata locks acquired by current statement and try to wait until they can be re-acquired. - Adjusted tdc_wait_for_old_versions() to check if there is someone waiting for one of metadata locks held by this connection and run deadlock detection in order to avoid deadlocks in some situations. - Added mysql_abort_transactions_with_shared_lock() callback which allows to force transactions holding shared metadata lock on the table to call MDL_context::can_wait_lead_to_deadlock() even if they don't need any new metadata locks so they can detect potential deadlocks between metadata locking subsystem and table-level locks. - Adjusted wait_while_table_is_used() not to set TABLE::version to 0 as it is now done only when necessary by the above-mentioned callback. Also removed unnecessary call to mysql_lock_abort(). Instead we rely on code performing metadata lock upgrade aborting waits on the table-level lock for this table by calling mysql_lock_abort_for_thread() (invoked by mysql_notify_thread_having_shared_lock()). In future this should allow to reduce number of scenarios in which we produce ER_LOCK_DEADLOCK error even though no real deadlock exists. sql/sql_class.h: Introduced Open_table_context::m_start_of_statement_svp member to store state of metadata locks at the start of the statement. Replaced Open_table_context::m_can_deadlock member with m_has_locks member to reflect the fact that we no longer unconditionally emit ER_LOCK_DEADLOCK error for transaction having some metadata locks when conflicting metadata lock is discovered. sql/sql_insert.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_plist.h: Made I_P_List_iterator<T, B> usable with const lists. sql/sql_show.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_update.cc: Changed UPDATE and MULTI-UPDATE code not to release all metadata locks when calls to mysql_lock_tables() are aborted. Instead we release only locks which are acquired by this statement and then try to reacquire them by calling open_tables(). This solves bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER".
-
- 29 Dec, 2009 3 commits
-
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
Konstantin Osipov authored
3655 Jon Olav Hauglid 2009-10-19 Bug #30977 Concurrent statement using stored function and DROP FUNCTION breaks SBR Bug #48246 assert in close_thread_table Implement a fix for: Bug #41804 purge stored procedure cache causes mysterious hang for many minutes Bug #49972 Crash in prepared statements The problem was that concurrent execution of DML statements that use stored functions and DDL statements that drop/modify the same function might result in incorrect binary log in statement (and mixed) mode and therefore break replication. This patch fixes the problem by introducing metadata locking for stored procedures and functions. This is similar to what is done in Bug#25144 for views. Procedures and functions now are locked using metadata locks until the transaction is either committed or rolled back. This prevents other statements from modifying the procedure/function while it is being executed. This provides commit ordering - guaranteeing serializability across multiple transactions and thus fixes the reported binlog problem. Note that we do not take locks for top-level CALLs. This means that procedures called directly are not protected from changes by simultaneous DDL operations so they are executed at the state they had at the time of the CALL. By not taking locks for top-level CALLs, we still allow transactions to be started inside procedures. This patch also changes stored procedure cache invalidation. Upon a change of cache version, we no longer invalidate the entire cache, but only those routines which we use, only when a statement is executed that uses them. This patch also changes the logic of prepared statement validation. A stored procedure used by a prepared statement is now validated only once a metadata lock has been acquired. A version mismatch causes a flush of the obsolete routine from the cache and statement reprepare. Incompatible changes: 1) ER_LOCK_DEADLOCK is reported for a transaction trying to access a procedure/function that is locked by a DDL operation in another connection. 2) Procedure/function DDL operations are now prohibited in LOCK TABLES mode as exclusive locks must be taken all at once and LOCK TABLES provides no way to specifiy procedures/functions to be locked. Test cases have been added to sp-lock.test and rpl_sp.test. Work on this bug has very much been a team effort and this patch includes and is based on contributions from Davi Arnaut, Dmitry Lenev, Magne Mæhre and Konstantin Osipov. mysql-test/r/ps_ddl.result: Update results (Bug#30977). mysql-test/r/ps_ddl1.result: Update results (Bug#30977). mysql-test/r/sp-error.result: Update results (Bug#30977). mysql-test/r/sp-lock.result: Update results (Bug#30977). mysql-test/suite/rpl/r/rpl_sp.result: Update results (Bug#30977). mysql-test/suite/rpl/t/rpl_sp.test: Add a test case for Bug#30977. mysql-test/t/ps_ddl.test: Update comments. We no longer re-prepare a prepared statement when a stored procedure used in top-level CALL is changed. mysql-test/t/ps_ddl1.test: Modifying stored procedure p1 no longer invalidates prepared statement "call p1" -- we can re-use the prepared statement without invalidation. mysql-test/t/sp-error.test: Use a constant for an error value. mysql-test/t/sp-lock.test: Add test coverage for Bug#30977. sql/lock.cc: Implement lock_routine_name() - a way to acquire an exclusive metadata lock (ex- name-lock) on stored procedure/function. sql/sp.cc: Change semantics of sp_cache_routine() -- now it has an option to make sure that the routine that is cached is up to date (has the latest sp cache version). Add sp_cache_invalidate() to sp_drop_routine(), where it was missing (a bug!). Acquire metadata locks for SP DDL (ALTER/CREATE/DROP). This is the core of the fix for Bug#30977. Since caching and cache invalidation scheme was changed, make sure we don't invalidate the SP cache in the middle of a stored routine execution. At the same time, make sure we don't access stale data due to lack of invalidation. For that, change ALTER FUNCTION/PROCEDURE to not use the cache, and SHOW PROCEDURE CODE/SHOW CREATE PROCEDURE/FUNCTION to always read an up to date version of the routine from the cache. sql/sp.h: Add a helper wrapper around sp_cache_routine(). sql/sp_cache.cc: Implement new sp_cache_version() and sp_cache_flush_obsolete(). Now we flush stale routines individually, rather than all at once. sql/sp_cache.h: Update signatures of sp_cache_version() and sp_cache_flush_obsolete(). sql/sp_head.cc: Add a default initialization of sp_head::m_sp_cache_version. Remove a redundant sp_head::create(). sql/sp_head.h: Add m_sp_cache_version to sp_head class - we now keep track of every routine in the stored procedure cache, rather than of the entire cache. sql/sql_base.cc: Implement prelocking for stored routines. Validate stored routines after they were locked. Flush obsolete routines upon next access, one by one, not all at once (Bug#41804). Style fixes. sql/sql_class.h: Rename a Open_table_context method. sql/sql_parse.cc: Make sure stored procedures DDL commits the active transaction (issues an implicit commit before and after). Remove sp_head::create(), a pure redundancy. Move the semantical check during alter routine inside sp_update_routine() code in order to: - avoid using SP cache during update, it may be obsolete. - speed up and simplify the update procedure. Remove sp_cache_flush_obsolete() calls, we no longer flush the entire cache, ever, stale routines are flushed before next use, one at a time. sql/sql_prepare.cc: Move routine metadata validation to open_and_process_routine(). Fix Bug#49972 (don't swap flags at reprepare). Reset Sroutine_hash_entries in reinit_stmt_before_use(). Remove SP cache invalidation, it's now done by open_tables(). sql/sql_show.cc: Fix a warning: remove an unused label. sql/sql_table.cc: Reset mdl_request.ticket for tickets acquired for routines inlined through a view, in CHECK TABLE statement, to satisfy an MDL assert. sql/sql_update.cc: Move the cleanup of "translation items" to close_tables_for_reopen(), since it's needed in all cases when we back off, not just the back-off in multi-update. This fixes a bug when the server would crash on attempt to back off when opening tables for a statement that uses information_schema tables.
-
- 22 Dec, 2009 1 commit
-
-
Konstantin Osipov authored
"HANDLER statements within a transaction might lead to deadlocks". Introduce a notion of a sentinel to MDL_context. A sentinel is a ticket that separates all tickets in the context into two groups: before and after it. Currently we can have (and need) only one designated sentinel -- it separates all locks taken by LOCK TABLE or HANDLER statement, which must survive COMMIT and ROLLBACK and all other locks, which must be released at COMMIT or ROLLBACK. The tricky part is maintaining the sentinel up to date when someone release its corresponding ticket. This can happen, e.g. if someone issues DROP TABLE under LOCK TABLES (generally, see all calls to release_all_locks_for_name()). MDL_context::release_ticket() is modified to take care of it. ****** A fix and a test case for Bug#46224 "HANDLER statements within a transaction might lead to deadlocks". An attempt to mix HANDLER SQL statements, which are transaction- agnostic, an open multi-statement transaction, and DDL against the involved tables (in a concurrent connection) could lead to a deadlock. The deadlock would occur when HANDLER OPEN or HANDLER READ would have to wait on a conflicting metadata lock. If the connection that issued HANDLER statement also had other metadata locks (say, acquired in scope of a transaction), a classical deadlock situation of mutual wait could occur. Incompatible change: entering LOCK TABLES mode automatically closes all open HANDLERs in the current connection. Incompatible change: previously an attempt to wait on a lock in a connection that has an open HANDLER statement could wait indefinitely/deadlock. After this patch, an error ER_LOCK_DEADLOCK is produced. The idea of the fix is to merge thd->handler_mdl_context with the main mdl_context of the connection, used for transactional locks. This makes deadlock detection possible, since all waits with locks are "visible" and available to analysis in a single MDL context of the connection. Since HANDLER locks and transactional locks have a different life cycle -- HANDLERs are explicitly open and closed, and so are HANDLER locks, explicitly acquired and released, whereas transactional locks "accumulate" till the end of a transaction and are released only with COMMIT, ROLLBACK and ROLLBACK TO SAVEPOINT, a concept of "sentinel" was introduced to MDL_context. All locks, HANDLER and others, reside in the same linked list. However, a selected element of the list separates locks with different life cycle. HANDLER locks always reside at the end of the list, after the sentinel. Transactional locks are prepended to the beginning of the list, before the sentinel. Thus, ROLLBACK, COMMIT or ROLLBACK TO SAVEPOINT, only release those locks that reside before the sentinel. HANDLER locks must be released explicitly as part of HANDLER CLOSE statement, or an implicit close. The same approach with sentinel is also employed for LOCK TABLES locks. Since HANDLER and LOCK TABLES statement has never worked together, the implementation is made simple and only maintains one sentinel, which is used either for HANDLER locks, or for LOCK TABLES locks. mysql-test/include/handler.inc: Add test coverage for Bug#46224 "HANDLER statements within a transaction might lead to deadlocks". Extended HANDLER coverage to cover a mix of HANDLER, transactions and DDL statements. mysql-test/r/handler_innodb.result: Update results (Bug#46224). mysql-test/r/handler_myisam.result: Update results (Bug#46224). sql/lock.cc: Remove thd->some_tables_deleted, it's never used. sql/log_event.cc: No need to check for thd->locked_tables_mode, it's done inside release_transactional_locks(). sql/mdl.cc: Implement the concept of HANDLER and LOCK TABLES "sentinel". Implement a method to clone an acquired ticket. Do not return tickets beyond the sentinel when acquiring locks, create a copy. Remove methods to merge and backup MDL_context, they are now not used (Hurra!). This opens a path to a proper constructor and destructor of class MDL_context (to be done in a separate patch). Modify find_ticket() to provide information about where the ticket position is with regard to the sentinel. sql/mdl.h: Add declarations necessary for the implementation of the concept of "sentinel", a dedicated ticket separating transactional and non-transactional locks. sql/mysql_priv.h: Add mark_tmp_table_for_reuse() declaration, a function to "close" a single session (temporary) table. sql/sql_base.cc: Remove thd->some_tables_deleted. Modify deadlock-prevention asserts and deadlock detection heuristics to take into account that from now on HANDLER locks reside in the same locking context. Add broadcast_refresh() to mysql_notify_thread_having_shared_lock(): this is necessary for the case when a thread having a shared lock is asleep in tdc_wait_for_old_versions(). This situation is only possible with HANDLER t1 OPEN; FLUSH TABLE (since all over code paths that lead to tdc_wait_for_old_versions() always have an empty MDL_context). Previously the server would simply deadlock in this situation. sql/sql_class.cc: Remove now unused member "THD::some_tables_deleted". Move mysql_ha_cleanup() a few lines above in THD::cleanup() to make sure that all handlers are closed when it's time to destroy the MDL_context of this connection. Remove handler_mdl_context and handler_tables. sql/sql_class.h: Remove THD::handler_tables, THD::handler_mdl_context, THD::some_tables_deleted. sql/sql_handler.cc: Remove thd->handler_tables. Remove thd->handler_mdl_context. Rewrite mysql_ha_open() to have no special provision for MERGE tables, now that we don't have to manipulate with thd->handler_tables it's easy to do. Remove dead code. Fix a bug in mysql_ha_flush() when we would always flush a temporary HANDLER when mysql_ha_flush() is called (actually mysql_ha_flush() never needs to flush temporary tables). sql/sql_insert.cc: Update a comment, no more thd->some_tables_deleted. sql/sql_parse.cc: Implement an incompatible change: entering LOCK TABLES closes active HANDLERs, if any. Now that we have a sentinel, we don't need to check for thd->locked_tables_mode when releasing metadata locks in COMMIT/ROLLBACK. sql/sql_plist.h: Add new (now necessary) methods to the list class. sql/sql_prepare.cc: Make sure we don't release HANDLER locks when rollback to a savepoint, set to not keep locks taken at PREPARE. sql/sql_servers.cc: Update to a new signature of MDL_context::release_all_locks(). sql/sql_table.cc: Remove thd->some_tables_deleted. sql/transaction.cc: Add comments. Make sure rollback to (MDL) savepoint works under LOCK TABLES and with HANDLER tables.
-
- 17 Dec, 2009 2 commits
-
-
Jon Olav Hauglid authored
------------------------------------------------------------ revno: 2617.14.26 committer: Vladislav Vaintroub <vvaintroub@mysql.com> branch nick: mysql-6.0-wtf timestamp: Wed 2008-11-05 11:19:19 +0100 message: CMakeLists.txt files cleanup. - remove SAFEMALLOC and SAFE_MUTEX definitions that were present in *each* CMakeLists.txt. Instead, put them into top level MakeLists.txt, but disable on Windows, because a) SAFEMALLOC does not add any functionality that is not already present in Debug C runtime ( and 2 safe malloc one on top of the other only unnecessarily slows down the server) b)SAFE_MUTEX does not work on Windows and have been explicitely disabled on Windows with #undef previously. Fortunately, ntdll does pretty good job identifying l problems with CRITICAL_SECTIONs. (DebugBreak()s on using uninited critical section, unlocking unowned critical section) -Remove occationally used -D_DEBUG (added by compiler anyway) -Remove MAP file generation, it became obsolete . There are many ways to get callstack of a crash now, with stacktrace in error log , minidump etc
-
Jon Olav Hauglid authored
If the handler (or delayed insert) thread failed to lock a table due to being killed, the "dead" flag was used to notify the connection thread of this failure. However, with the changes introduced by Bug#45949, the handler thread will no longer try to lock the table if it was killed. This meant that the "dead" flag would not be set, and the connection thread would not notice that the handler thread had failed. This could happen with concurrent INSERT DELAYED and FLUSH TABLES. FLUSH TABLES would kill any active INSERT DELAYED that had opened any table(s) to be flushed. This could cause the INSERT DELAYED connection thread to be stuck waiting for the handler thread to lock its table, while the handler thread would be looping, trying to get the connection thread to notice the error. The root of the problem was that the handler thread had both the "dead" flag and "thd->killed" to indicate that it had been killed. Most places both were set, but some only set "thd->killed". And Delayed_insert::get_local_table() only checked "dead" while waiting for the table to be locked. This patch removes the "dead" variable and replaces its usage with "thd->killed", thereby resolving the issue.
-
- 16 Dec, 2009 4 commits
-
-
Jon Olav Hauglid authored
The reason for the deadlock was an improper exit from MDL_context::wait_for_locks() which caused mysys_var->current_mutex to remain LOCK_mdl even though LOCK_mdl was no longer held by that connection. This could for example lead to a deadlock in the following way: 1) INSERT DELAYED tries to open a table but fails, and trying to recover it calls wait_for_locks(). 2) Due to a pending exclusive request, wait_for_locks() fails and exits without resetting mysys_var->current_mutex for the delayed insert handler thread. So it continues to point to LOCK_mdl. 3) The handler thread manages to open a table. 4) A different connection takes LOCK_open and tries to take LOCK_mdl. 5) FLUSH TABLES from a third connection notices that the handler thread has a table open, and tries to kill it. This involves locking mysys_var->current_mutex while having LOCK_open locked. Since current_mutex mistakenly points to LOCK_mdl, we have a deadlock. This patch makes sure MDL_EXIT_COND() is called before exiting wait_for_locks(). This clears mysys->current_mutex which resolves the issue. An assert is added to recover_from_failed_open_table_attempt() after wait_for_locks() is called, to check that current_mutex is indeed reset. With this assert in place, existing tests in (e.g.) mdl_sync.test will fail without this patch.
-
Konstantin Osipov authored
-
Konstantin Osipov authored
the fix for Bug#37148, since it is null-merged into 6.0.
-
Konstantin Osipov authored
-
- 15 Dec, 2009 4 commits
-
-
Konstantin Osipov authored
-
Konstantin Osipov authored
-
Konstantin Osipov authored
-
Jon Olav Hauglid authored
This deadlock would occur between two connections A and B if statements where executed in the following way: 1) Connection A executes a DML statement against table s1.t1 with autocommit off. This causes a shared metadata lock on s1.t1 to be acquired. (With autocommit on, the metadata lock will be dropped once the statment completes and the deadlock will not occour.) 2) Connection B tries to DROP DATABASE s1. This will block against the metadata lock connection A holds on s1.t1. While blocking, connection B will hold the LOCK_mysql_create_db mutex. 3) Connection A tries to ALTER DATABASE s1. This will block when trying to get LOCK_mysql_create_db mutex held by connection B. 4) Deadlock between DROP DATABASE and ALTER DATABASE (which has autocommit off). If Connection A used an explicitly started transaction rather than having autocommit off, this deadlock did not happen as ALTER DATABASE is disallowed inside transactions. This patch fixes the problem by changing ALTER DATABASE to cause an implicit commit before executing. This will cause the metadata lock on s1.t1 to be dropped, allowing DROP DATABASE to proceed. This will in turn cause the LOCK_mysql_create_db mutex to be unlocked, allowing ALTER DATABASE to proceed. Note that SQL commands other than ALTER DATABASE that also use LOCK_mysql_create_db, already cause an implicit commit. Incompatible change: ALTER DATABASE (and its synonym ALTER SCHEMA) now cause an implicit commit. This must be reflected in the documentation. Test case added to schema.test. sql/sql_parse.cc: Added CF_AUTO_COMMIT_TRANS to SQLCOM_ALTER_DB. Removed thd->active_transaction() checks from SQLCOM_DROP_DB, SQLCOM_ALTER_DB_UPGRADE and SQLCOM_ALTER_DB as these statements cause an implicit commit.
-
- 11 Dec, 2009 11 commits
-
-
Konstantin Osipov authored
------------------------------------------------------------ 2599.161.3 Ingo Struewing 2009-07-21 Bug#20667 - Truncate table fails for a write locked table TRUNCATE TABLE was not allowed under LOCK TABLES. The patch removes this restriction. mysql_truncate() does now handle that case. mysql-test/r/merge.result: Bug#20667 - Truncate table fails for a write locked table Updated test result. mysql-test/r/truncate.result: Bug#20667 - Truncate table fails for a write locked table Updated test result. mysql-test/r/truncate_coverage.result: Bug#20667 - Truncate table fails for a write locked table New test result. mysql-test/t/merge.test: Bug#20667 - Truncate table fails for a write locked table Updated test case due to now working TRUNCATE under LOCK TABLES. Added some SELECTs to show that child tables are truncated. mysql-test/t/truncate.test: Bug#20667 - Truncate table fails for a write locked table Added test cases for TRUNCATE under LOCK TABLE. mysql-test/t/truncate_coverage.test: Bug#20667 - Truncate table fails for a write locked table New test file. Coverage tests for TRUNCATE. sql/sql_delete.cc: Bug#20667 - Truncate table fails for a write locked table Added branches for thd->locked_tables_mode. sql/sql_parse.cc: Bug#20667 - Truncate table fails for a write locked table Deleted rejection of TRUNCATE in case of LOCK TABLES.
-
Konstantin Osipov authored
----------------------------------------------------------- 2630.28.28 Magne Mahre 2008-12-05 Bug #38661 'all threads hang in "opening tables" or "waiting for table" and cpu is at 100%' Concurrent execution of FLUSH TABLES statement and at least two statements using the same table might have led to live-lock which caused all three connections to stall and hog 100% of CPU. tdc_wait_for_old_versions() wrongly assumed that there cannot be a share with an old version and no used TABLE instances and thus was failing to perform wait in situation when such old share was cached in MDL subsystem thanks to a still active metadata lock on the table. So it might have happened that two or more connections simultaneously executing statements which involve table being flushed managed to prevent each other from waiting in this function by keeping shared metadata lock on the table constantly active (i.e. one of the statements managed to take/hold this lock while other statements were calling tdc_wait_for_old_versions()). Thus they were forcing each other to loop infinitely in open_tables() - close_thread_tables_for_reopen() - tdc_wait_for_old_versions() cycle causing CPU hogging. This patch fixes this problem by removing this false assumption from tdc_wait_for_old_versions(). Note that the problem is specific only for server versions >= 6.0. No test case is submitted for this test, as the test infrastructure hasn't got the necessary primitives to test the behaviour. The manifestation is that throughput will decrease to a low level (possibly 0) after some time, and stay at that level. Several transactions will not complete. Manual testing can be done by running the code submitted by Shane Bester attached to the bug report. If the bug persists, the transaction thruput will almost immediately drop to near zero (shown as the transaction count output from the test program staying on a close to constant value, instead of increasing rapidly).
-
Konstantin Osipov authored
----------------------------------------------------------- 2497.392.1 Michael Widenius 2008-08-19 Fixes for Bug #38016 Maria: trying to access freed memory when committing a transaction. Don't write out states if they haven't changed. sql/sql_table.cc: Call extra(HA_EXTRA_PREPARE_FOR_RENAME) before renaming a table.
-
Konstantin Osipov authored
---------------------------------------------------- 2736.2.10 Michael Widenius 2008-10-22 Fix for bug#39395 Maria: ma_extra.c:286: maria_extra: Assertion `share->reopen == 1' failed sql/sql_base.cc: Race condition in wait_while_table_is_used() where a table used by another connection could be forced closed, but there was no protection against the other thread re-opening the table and trying to lock it again before the table was name locked by original thread.
-
Konstantin Osipov authored
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
Alexander Nozdrin authored
-
- 10 Dec, 2009 4 commits
-
-
Alexander Nozdrin authored
-
Magne Mahre authored
An error occuring in the execution of a stored procedure, called from do_select is masked, since the error condition is not propagated back to the caller (join->conds->val_int() returns a result value, and not an error code) An explicit check was added to see if the thd error code has been set, and if so, the loop status is set to the error state. Backport from 6.0-codebase (revid: 2617.68.31)
-
Magne Mahre authored
(diagnostics_area) Execution of CREATE TABLE ... SELECT statement was not atomic in the sense that concurrent statements trying to affect its target table might have sneaked in between the moment when the table was created and moment when it was filled according to SELECT clause. This resulted in inconsistent binary log, unexpected target table contents. In cases when concurrent statement was a DDL statement CREATE TABLE ... SELECT might have failed with ER_CANT_LOCK error. In more detail: Due to premature metadata lock downgrade which occured after CREATE TABLE SELECT statement created table but before it managed to obtain table-level lock on it other statements were allowed to open, lock and change target table in the middle of CREATE TABLE SELECT execution. This also meant that it was possible that CREATE TABLE SELECT would wait in mysql_lock_tables() when it was called for newly created table and that this wait could have been aborted by concurrent DDL. The latter led to execution of unexpected branch of code and CREATE TABLE SELECT ending with ER_CANT_LOCK error. The premature downgrade occured because open_table(), which was called for newly created table, decided that it is OK to downgrade metadata lock from exclusive to shared since table exists, even although it was not acquired within this call. This fix ensures that open_table() does not downgrade metadata lock if it is not acquired during its current invocation. Testing: The bug is exposed in a race condition, and is thus difficult to expose in a standard mysql-test-run test case. Instead, a stress test using the Random Query Generator (https://launchpad.net/randgen) will trip the problem occasionally. % perl runall.pl \ --basedir=<build dir> \ --mysqld=--table-lock-wait-timeout=5 \ --mysqld=--skip-safemalloc \ --grammar=conf/maria_bulk_insert.yy \ --reporters=ErrorLog,Backtrace,WinPackage \ --mysqld=--log-output=file \ --queries=100000 \ --threads=10 \ --engine=myisam Note: You will need a debug build to expose the bug When the bug is tripped, the server will abort and dump core. Backport from 6.0-codebase (revid: 2617.53.4)
-
Alexander Nozdrin authored
-