MySQL Bugs: #66906: Innodb_row_lock_time_max seems to have an overflow

Bug #66906	Innodb_row_lock_time_max seems to have an overflow
Submitted:	21 Sep 2012 12:16	Modified:	16 Apr 2013 12:24
Reporter:	Oli Sennhauser	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: InnoDB storage engine	Severity:	S3 (Non-critical)
Version:	5.5.24, 5.5.30	OS:	Linux
Assigned to:		CPU Architecture:	Any

Description:
SHOW GLOBAL STATUS shows some kind of overflow:

Innodb_row_lock_current_waits                  0
Innodb_row_lock_time                   452854317
Innodb_row_lock_time_avg                     579
Innodb_row_lock_time_max       18446744073709549 --> This smells like a MySQL bug!
Innodb_row_lock_waits                     781680

Timeouts are default so max value should be about 50000.

Version details are: Ver 14.14 Distrib 5.5.24, for Linux (x86_64) using readline 5.1. It is a Rackspace MySQL. I do not know how much they have modified the code.

How to repeat:
Unknown.

Suggested fix:
Avoid overflow.

Thank you for the report.

Verified as described using code analysis.

Problem is in file storage/innobase/srv/srv0srv.c :

1711         if (thr->lock_state == QUE_THR_LOCK_ROW) {
1712                 if (ut_usectime(&sec, &ms) == -1) {
1713                         finish_time = -1;
1714                 } else {
1715                         finish_time = (ib_int64_t) sec * 1000000 + ms;
1716                 }
1717 
1718                 diff_time = (ulint) (finish_time - start_time);
1719 
1720                 srv_n_lock_wait_current_count--;
1721                 srv_n_lock_wait_time = srv_n_lock_wait_time + diff_time;
1722                 if (diff_time > srv_n_lock_max_wait_time &&
1723                     /* only update the variable if we successfully
1724                     retrieved the start and finish times. See Bug#36819. */
1725                     start_time != -1 && finish_time != -1) {
1726                         srv_n_lock_max_wait_time = diff_time;
1727                 }

Added a changelog entry for 5.5.32, 5.7.2:

An overflow would occur for "innodb_row_lock_time_max" and
"innodb_row_lock_current_waits". This fix modifies code logic in
"storage/innobase/srv/srv0srv.c".