MDEV-30658 lock_row_lock_current_waits counter in...

MDEV-30658 lock_row_lock_current_waits counter in information_schema.innodb_metrics may become negative

MONITOR_OVLD_ROW_LOCK_CURRENT_WAIT monitor should has
MONITOR_DISPLAY_CURRENT flag set in its definition, as it shows the
current state and does not accumulate anything.

Reviewed by: Marko Mäkelä

mysql-test/suite/innodb/r/innodb_skip_innodb_is_tables.result

@@ -50,7 +50,7 @@ lock_rec_locks	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabl
 lock_table_lock_created	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	counter	Number of table locks created
 lock_table_lock_removed	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	counter	Number of table locks removed from the lock queue
 lock_table_locks	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	counter	Current number of table locks on tables
-lock_row_lock_current_waits	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	status_counter	Number of row locks currently being waited for (innodb_row_lock_current_waits)
+lock_row_lock_current_waits	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	value	Number of row locks currently being waited for (innodb_row_lock_current_waits)
 lock_row_lock_time	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	status_counter	Time spent in acquiring row locks, in milliseconds (innodb_row_lock_time)
 lock_row_lock_time_max	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	value	The maximum time to acquire a row lock, in milliseconds (innodb_row_lock_time_max)
 lock_row_lock_waits	lock	0	NULL	NULL	NULL	0	NULL	NULL	NULL	NULL	NULL	NULL	NULL	disabled	status_counter	Number of times a row lock had to be waited for (innodb_row_lock_waits)

mysql-test/suite/innodb/r/mon_lock_wait_current_count.result

+connect  prevent_purge,localhost,root,,;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection default;
+SET GLOBAL innodb_monitor_disable='all';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+CREATE TABLE `t` (a INT PRIMARY KEY) engine=InnoDB STATS_PERSISTENT=0;
+INSERT INTO t VALUES (5);
+SELECT name, count FROM information_schema.innodb_metrics
+WHERE name ='lock_row_lock_current_waits';
+name	count
+lock_row_lock_current_waits	0
+connect  con1,localhost,root,,;
+BEGIN;
+SELECT * FROM t FOR UPDATE;
+a
+5
+connect  con2,localhost,root,,;
+SET DEBUG_SYNC="lock_wait_before_suspend SIGNAL blocked WAIT_FOR cont";
+BEGIN;
+SELECT * FROM t FOR UPDATE;
+connection default;
+SET DEBUG_SYNC="now WAIT_FOR blocked";
+SELECT name, count FROM information_schema.innodb_metrics
+WHERE name ='lock_row_lock_current_waits';
+name	count
+lock_row_lock_current_waits	1
+SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+SELECT name, count FROM information_schema.innodb_metrics
+WHERE name ='lock_row_lock_current_waits';
+name	count
+lock_row_lock_current_waits	1
+SET DEBUG_SYNC="now SIGNAL cont";
+disconnect con1;
+connection con2;
+a
+5
+COMMIT;
+disconnect con2;
+connection default;
+SET DEBUG_SYNC="reset";
+SELECT name, count FROM information_schema.innodb_metrics
+WHERE name ='lock_row_lock_current_waits';
+name	count
+lock_row_lock_current_waits	0
+DROP TABLE `t`;
+SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_disable=default;
+SET GLOBAL innodb_monitor_reset_all=default;
+SET GLOBAL innodb_monitor_enable=default;
+disconnect prevent_purge;

mysql-test/suite/innodb/t/mon_lock_wait_current_count.test

+# Check if lock_row_lock_current_waits counter in
+# information_schema.innodb_metrics does not become negative after disabling,
+# resetting and enabling.
+
+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/count_sessions.inc
+
+--connect (prevent_purge,localhost,root,,)
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+--connection default
+SET GLOBAL innodb_monitor_disable='all';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+CREATE TABLE `t` (a INT PRIMARY KEY) engine=InnoDB STATS_PERSISTENT=0;
+INSERT INTO t VALUES (5);
+SELECT name, count FROM information_schema.innodb_metrics
+  WHERE name ='lock_row_lock_current_waits';
+
+--connect (con1,localhost,root,,)
+BEGIN;
+SELECT * FROM t FOR UPDATE;
+
+--connect (con2,localhost,root,,)
+SET DEBUG_SYNC="lock_wait_before_suspend SIGNAL blocked WAIT_FOR cont";
+BEGIN;
+--send SELECT * FROM t FOR UPDATE
+
+--connection default
+SET DEBUG_SYNC="now WAIT_FOR blocked";
+SELECT name, count FROM information_schema.innodb_metrics
+  WHERE name ='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+######################################
+# Equals to zero if the bug is not fixed, as MONITOR_DISPLAY_CURRENT is not
+# set for this counter and its value is reset during previous
+# "SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits'" execution.
+#####
+SELECT name, count FROM information_schema.innodb_metrics
+  WHERE name ='lock_row_lock_current_waits';
+SET DEBUG_SYNC="now SIGNAL cont";
+
+--disconnect con1
+
+--connection con2
+--reap
+COMMIT;
+--disconnect con2
+
+--connection default
+SET DEBUG_SYNC="reset";
+######################################
+# Equals to -1 if the bug is not fixed. I.e.
+# innodb_counter_value[MONITOR_OVLD_ROW_LOCK_CURRENT_WAIT].mon_start_value is
+# set to 1 during
+# "set global innodb_monitor_disable='lock_row_lock_current_waits'" execution,
+# and the value is counted as
+# (value = 0) - (mon_value_reset = 0) - (mon_start_value = 1) +
+# (mon_last_value = 0) = -1. See MONITOR_SET_DIFF() macro in
+# srv_mon_process_existing_counter() for details.
+#####
+SELECT name, count FROM information_schema.innodb_metrics
+  WHERE name ='lock_row_lock_current_waits';
+DROP TABLE `t`;
+SET GLOBAL innodb_monitor_disable='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_reset_all='lock_row_lock_current_waits';
+SET GLOBAL innodb_monitor_enable='lock_row_lock_current_waits';
+--disable_warnings
+SET GLOBAL innodb_monitor_disable=default;
+SET GLOBAL innodb_monitor_reset_all=default;
+SET GLOBAL innodb_monitor_enable=default;
+--enable_warnings
+--disconnect prevent_purge
+--source include/wait_until_count_sessions.inc

storage/innobase/lock/lock0wait.cc

@@ -340,6 +340,7 @@ lock_wait_suspend_thread(
 		thd_wait_begin(trx->mysql_thd, THD_WAIT_TABLE_LOCK);
 	}
 
+	DEBUG_SYNC_C("lock_wait_before_suspend");
 	os_event_wait(slot->event);
 	DBUG_EXECUTE_IF("small_sleep_after_lock_wait",
 		{

storage/innobase/srv/srv0mon.cc

@@ -145,7 +145,7 @@ static monitor_info_t	innodb_counter_info[] =
 	 "Number of row locks currently being waited for"
 	 " (innodb_row_lock_current_waits)",
 	 static_cast<monitor_type_t>(
-	 MONITOR_EXISTING | MONITOR_DEFAULT_ON),
+	 MONITOR_EXISTING | MONITOR_DISPLAY_CURRENT | MONITOR_DEFAULT_ON),
 	 MONITOR_DEFAULT_START, MONITOR_OVLD_ROW_LOCK_CURRENT_WAIT},
 
 	{"lock_row_lock_time", "lock",