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MDEV-23586 Mariabackup: GTID saved for replication in 10.4.14 is wrong

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MDEV-21953 deadlock between BACKUP STAGE BLOCK_COMMIT and parallel
replication

Fixed by partly reverting MDEV-21953 to put back MDL_BACKUP_COMMIT locking
before log_and_order.

The original problem for MDEV-21953 was that while a thread was waiting in
for another threads to commit in 'log_and_order', it had the
MDL_BACKUP_COMMIT lock. The backup thread was waiting to get the
MDL_BACKUP_WAIT_COMMIT lock, which blocks all new MDL_BACKUP_COMMIT locks.
This causes a deadlock as the waited-for thread can never get past the
MDL_BACKUP_COMMIT lock in ha_commit_trans.

The main part of the bug fix is to release the MDL_BACKUP_COMMIT lock while
a thread is waiting for other 'previous' threads to commit. This ensures
that no transactional thread keeps MDL_BACKUP_COMMIT while waiting, which
ensures that there are no deadlocks anymore.
This commit is contained in:
Monty
2020-09-07 10:38:12 +03:00
parent 3cdbaa04bd
commit 16ea692ed4
6 changed files with 134 additions and 59 deletions
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3
sql/sql_class.h
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@ -2200,7 +2200,10 @@ public:
rpl_io_thread_info *rpl_io_info;
rpl_sql_thread_info *rpl_sql_info;
} system_thread_info;
/* Used for BACKUP LOCK */
MDL_ticket *mdl_backup_ticket, *mdl_backup_lock;
/* Used to register that thread has a MDL_BACKUP_WAIT_COMMIT lock */
MDL_request *backup_commit_lock;
void reset_for_next_command(bool do_clear_errors= 1);
/*