Elena Stepanova added a comment - 2016-12-08 18:34 - edited I can get this error quite reliably with this crude injection: diff --git a/mysql-test/extra/rpl_tests/rpl_checksum.inc b/mysql-test/extra/rpl_tests/rpl_checksum.inc index 14664fd..44d3776 100644 --- a/mysql-test/extra/rpl_tests/rpl_checksum.inc +++ b/mysql-test/extra/rpl_tests/rpl_checksum.inc @@ -15,6 +15,9 @@ call mtr.add_suppression('Slave can not handle replication events with the check call mtr.add_suppression('Replication event checksum verification failed'); # due to C failure simulation call mtr.add_suppression('Relay log write failure: could not queue event from master'); +--disable_query_log +set @@global.debug_dbug='d,mdev11491'; +--enable_query_log call mtr.add_suppression('Master is configured to log replication events with checksum, but will not send such events to slaves that cannot process them'); # A. read/write access to the global vars: @@ -88,6 +91,10 @@ create table t1 (a int); flush logs; flush logs; flush logs; +--sleep 10 +--disable_query_log +set @@global.debug_dbug=''; +--enable_query_log sync_slave_with_master; #connection slave; diff --git a/sql/log.cc b/sql/log.cc index 45ab5c8..6e0a87b 100644 --- a/sql/log.cc +++ b/sql/log.cc @@ -9630,6 +9630,7 @@ binlog_background_thread(void *arg __attribute__((unused))) DEBUG_SYNC(thd, "binlog_background_thread_before_mark_xid_done"); /* Grab next pointer first, as mark_xid_done() may free the element. */ next= queue->next_in_queue; + DBUG_EXECUTE_IF("mdev11491", { my_sleep(1000000); };); mysql_bin_log.mark_xid_done(queue->binlog_id, true); queue= next; So, it's a race condition for really slow systems (disks?) when mark_xid_done is considerably delayed. We need to ensure that it happens before we rotate to the log which for which the position is later printed in the error message.

Elena Stepanova added a comment - 2016-12-08 18:54 https://github.com/MariaDB/server/commit/870d7589c6c4596b0f1a641add5071469e2c94a7