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.

1 files changed, 19 insertions, 0 deletions

diff --git a/mysql-test/t/log_tables.test b/mysql-test/t/log_tables.test
index 076f2e8bc3b..af6c34dec37 100644
--- a/mysql-test/t/log_tables.test
+++ b/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;