Fixed bug#56619 - Assertion failed during

ALTER TABLE RENAME, DISABLE KEYS.

The code of ALTER TABLE RENAME, DISABLE KEYS could
issue a commit while holding LOCK_open mutex.
This is a regression introduced by the fix for
Bug 54453.
This failed an assert guarding us against a potential
deadlock with connections trying to execute
FLUSH TABLES WITH READ LOCK.

The fix is to move acquisition of LOCK_open outside
the section that issues ha_autocommit_or_rollback().
LOCK_open is taken to protect against concurrent
operations with .frms and the table definition
cache, and doesn't need to cover the call to commit.

A test case added to innodb_mysql.test.

The patch is to be null-merged to 5.5, which
already has 54453 null-merged to it.

mysql-test/suite/innodb/r/innodb_mysql.result:
  Added test results for test for bug#56619.
mysql-test/suite/innodb/t/innodb_mysql.test:
  Added test for bug#56619.
sql/sql_table.cc:
  mysql_alter_table() modified: moved acquisition of LOCK_open
  after call to ha_autocommit_or_rollback.

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

@@ -2620,3 +2620,11 @@ t2	CREATE TABLE `t2` (
   CONSTRAINT `x` FOREIGN KEY (`fk`) REFERENCES `t1` (`pk`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 drop table t2, t1;
+#
+# Test for bug #56619 - Assertion failed during
+# ALTER TABLE RENAME, DISABLE KEYS
+#
+DROP TABLE IF EXISTS t1, t2;
+CREATE TABLE t1 (a INT, INDEX(a)) engine=innodb;
+ALTER TABLE t1 RENAME TO t2, DISABLE KEYS;
+DROP TABLE IF EXISTS t1, t2;

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

@@ -845,3 +845,16 @@ create table t2 (fk int, key x (fk),
                  constraint x foreign key (FK) references t1 (PK)) engine=InnoDB;
 show create table t2;
 drop table t2, t1;
+
+--echo #
+--echo # Test for bug #56619 - Assertion failed during
+--echo # ALTER TABLE RENAME, DISABLE KEYS
+--echo #
+--disable_warnings
+DROP TABLE IF EXISTS t1, t2;
+--enable_warnings
+CREATE TABLE t1 (a INT, INDEX(a)) engine=innodb;
+--disable_warnings
+ALTER TABLE t1 RENAME TO t2, DISABLE KEYS;
+DROP TABLE IF EXISTS t1, t2;
+--enable_warnings

sql/sql_table.cc

@@ -6832,7 +6832,6 @@ view_err:
 			  table->alias);
     }
 
-    VOID(pthread_mutex_lock(&LOCK_open));
     /*
       Unlike to the above case close_cached_table() below will remove ALL
       instances of TABLE from table cache (it will also remove table lock
@@ -6853,6 +6852,7 @@ view_err:
       */
       ha_autocommit_or_rollback(thd, 0);
 
+      VOID(pthread_mutex_lock(&LOCK_open));
       /*
         Then do a 'simple' rename of the table. First we need to close all
         instances of 'source' table.
@@ -6885,6 +6885,8 @@ view_err:
         }
       }
     }
+    else
+      VOID(pthread_mutex_lock(&LOCK_open));
 
     if (error == HA_ERR_WRONG_COMMAND)
     {