From 5d49a2add70123fa3a54db4c1e48b9246d2f208d Mon Sep 17 00:00:00 2001
From: Iaroslav Babanin <yvef@yahoo.com>
Date: Wed, 15 May 2024 17:42:08 +0300
Subject: [PATCH] MDEV-33935 fix deadlock counter

- The deadlock counter was moved from
Deadlock::find_cycle into Deadlock::report, because
the find_cycle method is called multiple times during deadlock
detection flow, which means it shouldn't have such side effects.
But report() can, which called only once for
a victim transaction.
- Also the deadlock_detect.test and *.result test case
has been extended to handle the fix.
---
 .../suite/innodb/r/deadlock_detect.result     |  8 +++++++
 .../suite/innodb/t/deadlock_detect.test       | 21 +++++++++++++++++--
 storage/innobase/include/srv0srv.h            |  1 -
 storage/innobase/lock/lock0lock.cc            |  2 +-
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/mysql-test/suite/innodb/r/deadlock_detect.result b/mysql-test/suite/innodb/r/deadlock_detect.result
index 8131585aea2..284556e56c9 100644
--- a/mysql-test/suite/innodb/r/deadlock_detect.result
+++ b/mysql-test/suite/innodb/r/deadlock_detect.result
@@ -3,7 +3,12 @@ CREATE TABLE t1(
 id	INT,
 PRIMARY KEY(id)
 ) ENGINE=InnoDB;
+CREATE TABLE dl(
+id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT, 
+cnt INT UNSIGNED
+) ENGINE=InnoDB;
 INSERT INTO t1 VALUES(1), (2), (3);
+INSERT INTO dl(cnt) SELECT variable_value FROM information_schema.global_status WHERE variable_name LIKE 'Innodb_deadlocks';
 BEGIN;
 SELECT * FROM t1 WHERE id = 1 LOCK IN SHARE MODE;
 connect  con1,localhost,root,,;
@@ -20,5 +25,8 @@ disconnect con1;
 ROLLBACK;
 disconnect con2;
 connection default;
+'Deadlock counter is valid';
+1
 ROLLBACK;
 DROP TABLE t1;
+DROP TABLE dl;
diff --git a/mysql-test/suite/innodb/t/deadlock_detect.test b/mysql-test/suite/innodb/t/deadlock_detect.test
index e853790755a..a84e6fc328f 100644
--- a/mysql-test/suite/innodb/t/deadlock_detect.test
+++ b/mysql-test/suite/innodb/t/deadlock_detect.test
@@ -14,7 +14,14 @@ CREATE TABLE t1(
 	PRIMARY KEY(id)
 ) ENGINE=InnoDB;
 
+CREATE TABLE dl(
+    id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT, 
+    cnt INT UNSIGNED
+) ENGINE=InnoDB;
+
 INSERT INTO t1 VALUES(1), (2), (3);
+# Preserve the initial value of the deadlock counter
+INSERT INTO dl(cnt) SELECT variable_value FROM information_schema.global_status WHERE variable_name LIKE 'Innodb_deadlocks';
 
 # We are not interested query results, only errors
 --disable_result_log
@@ -61,6 +68,7 @@ disconnect con2;
 # and does the update.
 #
 connection default;
+--let $valid_deadlock_cnt= 1
 if (!$have_deadlock) {
 --error 0,ER_LOCK_WAIT_TIMEOUT
 reap;
@@ -68,12 +76,21 @@ reap;
 if ($have_deadlock) {
 --error 0,ER_LOCK_DEADLOCK
 reap;
+--disable_query_log
+INSERT INTO dl(cnt) SELECT variable_value FROM information_schema.global_status WHERE variable_name LIKE 'Innodb_deadlocks';
+set @init_deadlock_cnt = (SELECT min(k.cnt) FROM dl k);
+--let $valid_deadlock_cnt= `SELECT (max(t.cnt-@init_deadlock_cnt) = 1) FROM dl t`
+--enable_query_log
 }
+# Indicates that the deadlock counter works well.
+# Use the default =1 where is no deadlock detection,
+# to enable unconditional check.
+--echo 'Deadlock counter is valid';
+--echo $valid_deadlock_cnt
 
 ROLLBACK;
 
 --enable_result_log
-
 DROP TABLE t1;
-
+DROP TABLE dl;
 --source include/wait_until_count_sessions.inc
diff --git a/storage/innobase/include/srv0srv.h b/storage/innobase/include/srv0srv.h
index dc0546ac0f3..4c3c17a1a16 100644
--- a/storage/innobase/include/srv0srv.h
+++ b/storage/innobase/include/srv0srv.h
@@ -668,7 +668,6 @@ struct export_var_t{
 	ulint innodb_data_reads;		/*!< I/O read requests */
 	ulint innodb_dblwr_pages_written;	/*!< srv_dblwr_pages_written */
 	ulint innodb_dblwr_writes;		/*!< srv_dblwr_writes */
-	ulint innodb_deadlocks;
 	ulint innodb_history_list_length;
 	ulint innodb_log_waits;			/*!< srv_log_waits */
 	ulint innodb_log_write_requests;	/*!< srv_log_write_requests */
diff --git a/storage/innobase/lock/lock0lock.cc b/storage/innobase/lock/lock0lock.cc
index 4d0ac5ccc04..3e3d573ba5b 100644
--- a/storage/innobase/lock/lock0lock.cc
+++ b/storage/innobase/lock/lock0lock.cc
@@ -296,7 +296,6 @@ namespace Deadlock
       if (tortoise == hare)
       {
         ut_ad(l > 1);
-        lock_sys.deadlocks++;
         /* Note: Normally, trx should be part of any deadlock cycle
         that is found. However, if innodb_deadlock_detect=OFF had been
         in effect in the past, it is possible that trx will be waiting
@@ -6825,6 +6824,7 @@ and less modified rows. Bit 0 is used to prefer orig_trx in case of a tie.
       if (!cycle)
         goto func_exit; /* One of the transactions was already aborted. */
 
+      lock_sys.deadlocks++;
       victim= cycle;
       undo_no_t victim_weight= calc_victim_weight(victim, trx);
       unsigned victim_pos= l;