From ddd3e261b253856720bd9dc2343a655ecc297e81 Mon Sep 17 00:00:00 2001
From: unknown <knielsen@knielsen-hq.org>
Date: Tue, 8 May 2012 14:27:44 +0200
Subject: [PATCH] MDEV-254: Server hang with FLUSH TABLES WITH READ LOCK AND
 DISABLE CHECKPOINT

The code to re-enable checkpointing after UNLOCK TABLES was lost in the 5.5
merge, so re-add it back in.
---
 mysql-test/r/flush-innodb.result | 5 +++++
 mysql-test/t/flush-innodb.test   | 9 +++++++++
 sql/lock.cc                      | 9 +++++++++
 3 files changed, 23 insertions(+)
 create mode 100644 mysql-test/r/flush-innodb.result
 create mode 100644 mysql-test/t/flush-innodb.test

diff --git a/mysql-test/r/flush-innodb.result b/mysql-test/r/flush-innodb.result
new file mode 100644
index 00000000000..cea4f81e2a2
--- /dev/null
+++ b/mysql-test/r/flush-innodb.result
@@ -0,0 +1,5 @@
+FLUSH TABLES WITH READ LOCK AND DISABLE CHECKPOINT;
+UNLOCK TABLES;
+CREATE TABLE t1 ( m MEDIUMTEXT ) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ( REPEAT('i',1048576) );
+DROP TABLE t1;
diff --git a/mysql-test/t/flush-innodb.test b/mysql-test/t/flush-innodb.test
new file mode 100644
index 00000000000..207032b1acb
--- /dev/null
+++ b/mysql-test/t/flush-innodb.test
@@ -0,0 +1,9 @@
+--source include/have_innodb.inc
+
+# MDEV-254: Server hang with FLUSH TABLES WITH READ LOCK AND DISABLE CHECKPOINT
+FLUSH TABLES WITH READ LOCK AND DISABLE CHECKPOINT;
+UNLOCK TABLES;
+CREATE TABLE t1 ( m MEDIUMTEXT ) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ( REPEAT('i',1048576) );
+
+DROP TABLE t1;
diff --git a/sql/lock.cc b/sql/lock.cc
index c5a4674bfb0..3a1a6d41ce3 100644
--- a/sql/lock.cc
+++ b/sql/lock.cc
@@ -1041,6 +1041,15 @@ void Global_read_lock::unlock_global_read_lock(THD *thd)
 
   DBUG_ASSERT(m_mdl_global_shared_lock && m_state);
 
+  if (thd->global_disable_checkpoint)
+  {
+    thd->global_disable_checkpoint= 0;
+    if (!--global_disable_checkpoint)
+    {
+      ha_checkpoint_state(0);                   // Enable checkpoints
+    }
+  }
+
   if (m_mdl_blocks_commits_lock)
   {
     thd->mdl_context.release_lock(m_mdl_blocks_commits_lock);