A fix and a test case for Bug#47924 -main.log_tables times out

sporadically.

The cause of the sporadic time out was a leaking protection
against the global read lock, taken by the RENAME statement,
and not released in case of an error occurred during RENAME.
The leaking protection counter would lead to the value of
protect_against_global_read never dropping to 0.
Consequently FLUSH TABLES in all connections, including the
one that leaked the protection, could not proceed.
 
The fix is to ensure that all branchesin RENAME code properly
release GRL protection.

mysql-test/r/log_tables.result:
  Added results for test for bug#47924.
mysql-test/t/log_tables.test:
  Added test for bug#47924.
sql/sql_rename.cc:
  mysql_rename_tables() modified: replaced return from function
  to goto to clean up code block in case of error.

mysql-test/r/log_tables.result

@@ -899,6 +899,16 @@ TIMESTAMP	1	1	SELECT SQL_NO_CACHE 'Bug#31700 - KEY', f1,f2,f3,SLEEP(1.1) FROM t1
 TIMESTAMP	1	1	SELECT SQL_NO_CACHE 'Bug#31700 - PK',  f1,f2,f3,SLEEP(1.1) FROM t1 WHERE f1=2
 DROP TABLE t1;
 TRUNCATE TABLE mysql.slow_log;
+use mysql;
+drop table if exists renamed_general_log;
+drop table if exists renamed_slow_log;
+RENAME TABLE general_log TO renamed_general_log;
+ERROR HY000: Cannot rename 'general_log'. When logging enabled, rename to/from log table must rename two tables: the log table to an archive table and another table back to 'general_log'
+RENAME TABLE slow_log TO renamed_slow_log;
+ERROR HY000: Cannot rename 'slow_log'. When logging enabled, rename to/from log table must rename two tables: the log table to an archive table and another table back to 'slow_log'
+use test;
+flush tables with read lock;
+unlock tables;
 SET @@session.long_query_time= @old_long_query_time;
 SET @@global.log_output=       @old_log_output;
 SET @@global.slow_query_log=   @old_slow_query_log;

mysql-test/t/log_tables.test

@@ -1027,6 +1027,25 @@ DROP TABLE t1;
 
 TRUNCATE TABLE mysql.slow_log;
 
+#
+# Bug #47924 main.log_tables times out sporadically
+#
+
+use mysql;
+# Should result in error
+--disable_warnings
+drop table if exists renamed_general_log;
+drop table if exists renamed_slow_log;
+--enable_warnings
+--error ER_CANT_RENAME_LOG_TABLE
+RENAME TABLE general_log TO renamed_general_log;
+--error ER_CANT_RENAME_LOG_TABLE
+RENAME TABLE slow_log TO renamed_slow_log;
+
+use test;
+flush tables with read lock;
+unlock tables;
+
 SET @@session.long_query_time= @old_long_query_time;
 
 SET @@global.log_output=       @old_log_output;

sql/sql_rename.cc

@@ -99,7 +99,7 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
             */
             my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), ren_table->table_name,
                      ren_table->table_name);
-            DBUG_RETURN(1);
+            goto err;
           }
         }
         else
@@ -112,7 +112,7 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
             */
             my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), ren_table->table_name,
                      ren_table->table_name);
-            DBUG_RETURN(1);
+            goto err;
           }
           else
           {
@@ -130,7 +130,7 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
       else
         my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), rename_log_table[1],
                  rename_log_table[1]);
-      DBUG_RETURN(1);
+      goto err;
     }
   }