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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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2
sql/handler.h
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@ -5024,7 +5024,7 @@ int ha_change_key_cache(KEY_CACHE *old_key_cache, KEY_CACHE *new_key_cache);
/* transactions: interface to handlerton functions */
int ha_start_consistent_snapshot(THD *thd);
int ha_commit_or_rollback_by_xid(XID *xid, bool commit);
int ha_commit_one_phase(THD *thd, bool all, bool rw_trans);
int ha_commit_one_phase(THD *thd, bool all);
int ha_commit_trans(THD *thd, bool all);
int ha_rollback_trans(THD *thd, bool all);
int ha_prepare(THD *thd);