| Bug #16501 | IS_USED_LOCK does not appear to work | ||
|---|---|---|---|
| Submitted: | 14 Jan 2006 0:42 | Modified: | 11 May 2006 17:06 |
| Reporter: | [ name withheld ] | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: General | Severity: | S3 (Non-critical) |
| Version: | 4.1.17-BK, 4.1.16 | OS: | Linux (Linux, Windows) |
| Assigned to: | Tomash Brechko | CPU Architecture: | Any |
[14 Jan 2006 9:53]
Valeriy Kravchuk
Thank you for a bug report. Verified just as described with 4.1.17-BK (ChangeSet@1.2475, 2006-01-11 17:31:52+03:00) on Linux. From the first session (connection id 5) I've got:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5 to server version: 4.1.17-log
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> SELECT GET_LOCK('42',600);
+--------------------+
| GET_LOCK('42',600) |
+--------------------+
| 1 |
+--------------------+
1 row in set (0.05 sec)
mysql> SELECT RELEASE_LOCK('42');
+--------------------+
| RELEASE_LOCK('42') |
+--------------------+
| 1 |
+--------------------+
1 row in set (0.01 sec)
mysql> SELECT IS_USED_LOCK('42');
+--------------------+
| IS_USED_LOCK('42') |
+--------------------+
| 5 |
+--------------------+
1 row in set (0.00 sec)
Note, that connection identifier is still 5. Connection identifier for the lock is not updated. This is a bug.
[22 Apr 2006 6:59]
Konstantin Osipov
We need to fix it before 4.1.20 release
[22 Apr 2006 17:35]
Konstantin Osipov
I wasn't able to repeat Valeriy's shortened test case, below is the patch that fixes the original problem:
===== item_func.cc 1.259 vs edited =====
--- 1.259/sql/item_func.cc 2006-04-12 23:02:02 +04:00
+++ edited/item_func.cc 2006-04-22 21:31:34 +04:00
@@ -1972,6 +1972,7 @@
void item_user_lock_release(User_level_lock *ull)
{
ull->locked=0;
+ ull->thread_id= 0;
if (mysql_bin_log.is_open())
{
char buf[256];
@@ -2170,6 +2171,7 @@
{
ull->locked=1;
ull->thread=thd->real_id;
+ ull->thread_id= thd->thread_id;
thd->ull=ull;
error=0;
}
(Tomash, this is just to save you investigation time).
[24 Apr 2006 14:05]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/5405
[24 Apr 2006 21:37]
Konstantin Osipov
Approved by email.
[6 May 2006 14:23]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/6056
[11 May 2006 10:38]
Tomash Brechko
Fixed in 4.1.20, 5.0.22, 5.1.11.
[11 May 2006 17:06]
Paul DuBois
Noted in 4.1.20, 5.0.22, 5.1.11 changelogs. <literal>IS_USED_LOCK()</literal> could return an incorrect connection identifier.
Description: IS_USED_LOCK can report the wrong connection identifier for a lock. How to repeat: Open up two connections to mysql, connection 1 and connection 2. Run the following statements, as designated by their connection: 1: SELECT GET_LOCK('42',600); 2: SELECT IS_USED_LOCK('42'); SELECT GET_LOCK('42',600); 1: SELECT RELEASE_LOCK('42'); SELECT IS_USED_LOCK('42'); Suggested fix: The last IS_USED_LOCK should report the connection identifier for connection 2, since connection 2 actually holds the lock.