database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00
Code Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

30
sql/sql_class.cc
View File

@ -1271,6 +1271,7 @@ void THD::init()
first_successful_insert_id_in_prev_stmt_for_binlog= 0;
first_successful_insert_id_in_cur_stmt= 0;
current_backup_stage= BACKUP_FINISHED;
backup_commit_lock= 0;
#ifdef WITH_WSREP
wsrep_last_query_id= 0;
wsrep_xid.null();
@ -1383,7 +1384,7 @@ void THD::init_for_queries()
set_time();
/*
We don't need to call ha_enable_transaction() as we can't have
any active transactions that has to be commited
any active transactions that has to be committed
*/
transaction.on= TRUE;
@ -7386,16 +7387,33 @@ wait_for_commit::register_wait_for_prior_commit(wait_for_commit *waitee)
}
/*
Wait for commit of another transaction to complete, as already registered
/**
Waits for commit of another transaction to complete, as already registered
with register_wait_for_prior_commit(). If the commit already completed,
returns immediately.
If thd->backup_commit_lock is set, release it while waiting for other threads
*/
int
wait_for_commit::wait_for_prior_commit2(THD *thd)
{
PSI_stage_info old_stage;
wait_for_commit *loc_waitee;
bool backup_lock_released= 0;
/*
Release MDL_BACKUP_COMMIT LOCK while waiting for other threads to commit
This is needed to avoid deadlock between the other threads (which not
yet have the MDL_BACKUP_COMMIT_LOCK) and any threads using
BACKUP LOCK BLOCK_COMMIT.
*/
if (thd->backup_commit_lock && thd->backup_commit_lock->ticket)
{
backup_lock_released= 1;
thd->mdl_context.release_lock(thd->backup_commit_lock->ticket);
thd->backup_commit_lock->ticket= 0;
}
mysql_mutex_lock(&LOCK_wait_commit);
DEBUG_SYNC(thd, "wait_for_prior_commit_waiting");
@ -7445,10 +7463,16 @@ wait_for_commit::wait_for_prior_commit2(THD *thd)
use within enter_cond/exit_cond.
*/
DEBUG_SYNC(thd, "wait_for_prior_commit_killed");
if (backup_lock_released)
thd->mdl_context.acquire_lock(thd->backup_commit_lock,
thd->variables.lock_wait_timeout);
return wakeup_error;
end:
thd->EXIT_COND(&old_stage);
if (backup_lock_released)
thd->mdl_context.acquire_lock(thd->backup_commit_lock,
thd->variables.lock_wait_timeout);
return wakeup_error;
}