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MDEV-35355 : Galera test failure on galera_sr.mysql-wsrep-features#165

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Problem was that in DeadlockChecker::trx_rollback() we hold lock_sys
before we call wsrep_handle_SR_rollback() where THD::LOCK_thd_data
(and some cases THD::LOCK_thd_kill) are acquired. This is against
current mutex ordering rules.

However, acquiring THD::LOCK_thd_data is not necessary because we
always are in victim_thd context, either client session is rolling
back or rollbacker thread should be in control. Therefore, we should
always use wsrep_thd_self_abort() and then no additional mutexes are
required.

Fixed by removing locking of THD::LOCK_thd_data and using only
wsrep_thd_self_abort(). In debug builds added assertions to
verify that we are always in victim_thd context.

This fix is for MariaDB 10.5 and we already have a test case
that sporadically fail in Jenkins before this fix.

Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
This commit is contained in:
Jan Lindström 2024-11-07 09:04:16 +02:00 committed by Julius Goryavsky
parent af50783fcd
commit f219fb8489
1 changed files with 11 additions and 24 deletions
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33
sql/service_wsrep.cc
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@ -186,44 +186,31 @@ extern "C" my_bool wsrep_thd_is_SR(const THD *thd)
return thd && thd->wsrep_cs().transaction().is_streaming();
}
extern "C" void wsrep_handle_SR_rollback(THD *bf_thd,
extern "C" void wsrep_handle_SR_rollback(THD *bf_thd __attribute__((unused)),
THD *victim_thd)
{
/*
We should always be in victim_thd context, either client session is
rolling back or rollbacker thread should be in control.
*/
DBUG_ASSERT(victim_thd);
DBUG_ASSERT(current_thd == victim_thd);
DBUG_ASSERT(wsrep_thd_is_SR(victim_thd));
if (!victim_thd || !wsrep_on(bf_thd)) return;
wsrep_thd_LOCK(victim_thd);
/* Defensive measure to avoid crash in production. */
if (!victim_thd) return;
WSREP_DEBUG("handle rollback, for deadlock: thd %llu trx_id %" PRIu64 " frags %zu conf %s",
WSREP_DEBUG("Handle SR rollback, for deadlock: thd %llu trx_id %" PRIu64 " frags %zu conf %s",
victim_thd->thread_id,
victim_thd->wsrep_trx_id(),
victim_thd->wsrep_sr().fragments_certified(),
wsrep_thd_transaction_state_str(victim_thd));
/* Note: do not store/reset globals before wsrep_bf_abort() call
to avoid losing BF thd context. */
if (!(bf_thd && bf_thd != victim_thd))
{
DEBUG_SYNC(victim_thd, "wsrep_before_SR_rollback");
}
if (bf_thd)
{
wsrep_bf_abort(bf_thd, victim_thd);
}
else
{
wsrep_thd_self_abort(victim_thd);
}
wsrep_thd_UNLOCK(victim_thd);
if (bf_thd)
{
wsrep_store_threadvars(bf_thd);
}
}
extern "C" my_bool wsrep_thd_bf_abort(THD *bf_thd, THD *victim_thd,
my_bool signal)
{