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MDEV-31448: Killing a replica thread awaiting its GCO can hang/crash a parallel replica

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The problem was an incorrect unmark_start_commit() in
signal_error_to_sql_driver_thread(). If an event group gets an error, this
unmark could run after the following GCO started, and the subsequent
re-marking could access de-allocated GCO.

The offending unmark_start_commit() looks obviously incorrect, and the fix
is to just remove it. It was introduced in the MDEV-8302 patch, the commit
message of which suggests it was added there solely to satisfy an assertion
in ha_rollback_trans(). So update this assertion instead to not trigger for
event groups that experienced an error (rgi->worker_error). When an error
occurs in an event group, all following event groups are skipped anyway, so
the unmark should never be needed in this case.

Reviewed-by: Andrei Elkin <andrei.elkin@mariadb.com>
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
This commit is contained in:
Kristian Nielsen
2023-06-11 17:44:58 +02:00
parent 60bec1d54d
commit a8ea6627a4
3 changed files with 15 additions and 7 deletions
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5
sql/rpl_parallel.cc
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@ -286,16 +286,11 @@ static void
signal_error_to_sql_driver_thread(THD *thd, rpl_group_info *rgi, int err)
{
rgi->worker_error= err;
/*
In case we get an error during commit, inform following transactions that
we aborted our commit.
*/
DBUG_EXECUTE_IF("hold_worker2_favor_worker3", {
if (rgi->current_gtid.seq_no == 2002) {
debug_sync_set_action(thd, STRING_WITH_LEN("now WAIT_FOR cont_worker2"));
}});
rgi->unmark_start_commit();
rgi->cleanup_context(thd, true);
rgi->rli->abort_slave= true;
rgi->rli->stop_for_until= false;