=== modified file 'mysql-test/r/information_schema.result'
--- a/mysql-test/r/information_schema.result	2012-12-18 10:44:15 +0000
+++ b/mysql-test/r/information_schema.result	2013-01-16 13:49:47 +0000
@@ -1931,6 +1931,15 @@
 #
 # Switching to connection 'default'.
 #
+#
+# MDEV-4029, Bug#58738: double locking mutex when querying i_s.session_status in query and it's subquery
+#
+SELECT * FROM information_schema.session_status 
+WHERE VARIABLE_NAME = (
+SELECT VARIABLE_NAME FROM information_schema.session_status WHERE VARIABLE_NAME = 'COM_BEGIN'
+);
+VARIABLE_NAME	VARIABLE_VALUE
+COM_BEGIN	0
 #
 # Clean-up.
 drop database mysqltest;

=== modified file 'mysql-test/t/information_schema.test'
--- a/mysql-test/t/information_schema.test	2012-12-18 10:44:15 +0000
+++ b/mysql-test/t/information_schema.test	2013-01-16 13:45:49 +0000
@@ -1808,6 +1808,14 @@
 disconnect con12828477_3;
 
 --echo #
+--echo # MDEV-4029, Bug#58738: double locking mutex when querying i_s.session_status in query and it's subquery
+--echo #
+SELECT * FROM information_schema.session_status 
+WHERE VARIABLE_NAME = (
+  SELECT VARIABLE_NAME FROM information_schema.session_status WHERE VARIABLE_NAME = 'COM_BEGIN'
+);
+
+--echo #
 --echo # Clean-up.
 drop database mysqltest;
 

=== modified file 'sql/sql_show.cc'
--- a/sql/sql_show.cc	2013-01-15 18:13:32 +0000
+++ b/sql/sql_show.cc	2013-01-16 13:52:36 +0000
@@ -2584,8 +2584,7 @@
                               enum enum_var_type value_type,
                               struct system_status_var *status_var,
                               const char *prefix, TABLE *table,
-                              bool ucase_names,
-                              COND *cond)
+                              bool ucase_names, COND* partial_cond)
 {
   my_aligned_storage<SHOW_VAR_FUNC_BUFF_SIZE, MY_ALIGNOF(long)> buffer;
   char * const buff= buffer.data;
@@ -2595,7 +2594,6 @@
   int len;
   LEX_STRING null_lex_str;
   SHOW_VAR tmp, *var;
-  COND *partial_cond= 0;
   enum_check_fields save_count_cuted_fields= thd->count_cuted_fields;
   bool res= FALSE;
   CHARSET_INFO *charset= system_charset_info;
@@ -2609,7 +2607,6 @@
   if (*prefix)
     *prefix_end++= '_';
   len=name_buffer + sizeof(name_buffer) - prefix_end;
-  partial_cond= make_cond_for_info_schema(cond, table->pos_in_table_list);
 
   for (; variables->name; variables++)
   {
@@ -6893,6 +6890,12 @@
   enum enum_var_type option_type= OPT_SESSION;
   bool upper_case_names= (schema_table_idx != SCH_VARIABLES);
   bool sorted_vars= (schema_table_idx == SCH_VARIABLES);
+  COND* partial_cond=
+    make_cond_for_info_schema(cond, tables->table->pos_in_table_list);
+  // this can trigger subquery execution and entry into this function again
+  // so we execute it before taking the lock to fill the table
+  if (partial_cond)
+    partial_cond->val_int();
 
   if (lex->option_type == OPT_GLOBAL ||
       schema_table_idx == SCH_GLOBAL_VARIABLES)
@@ -6900,7 +6903,7 @@
 
   mysql_rwlock_rdlock(&LOCK_system_variables_hash);
   res= show_status_array(thd, wild, enumerate_sys_vars(thd, sorted_vars, option_type),
-                         option_type, NULL, "", tables->table, upper_case_names, cond);
+                         option_type, NULL, "", tables->table, upper_case_names, partial_cond);
   mysql_rwlock_unlock(&LOCK_system_variables_hash);
   DBUG_RETURN(res);
 }
@@ -6917,6 +6920,12 @@
     get_schema_table_idx(tables->schema_table);
   enum enum_var_type option_type;
   bool upper_case_names= (schema_table_idx != SCH_STATUS);
+  COND* partial_cond=
+    make_cond_for_info_schema(cond, tables->table->pos_in_table_list);
+  // this can trigger subquery execution and reentrance into this function
+  // so we execute it before taking the mutex to fill the table
+  if (partial_cond)
+    partial_cond->val_int();
 
   if (schema_table_idx == SCH_STATUS)
   {
@@ -6943,7 +6952,7 @@
   res= show_status_array(thd, wild,
                          (SHOW_VAR *)all_status_vars.buffer,
                          option_type, tmp1, "", tables->table,
-                         upper_case_names, cond);
+                         upper_case_names, partial_cond);
   mysql_mutex_unlock(&LOCK_status);
   DBUG_RETURN(res);
 }