wrlock(LOCK_grant)                 -> lock(acl_cache->lock)               GRANT/REVOKE CREATE/DROP USER
lock(LOCK_open)                    -> rdlock(LOCK_grant)                  SELECT * FROM INFORMATION_SCHEMA.COLUMNS
wrlock(LOCK_logger)                -> lock(LOCK_open)                     SET @@global.slow_query_log='ON'
lock(acl_cache->lock)              -> rdlock(LOCK_logger)                 Failed connection

--source include/have_plugin_auth.inc
--source include/have_debug_sync.inc

SET @@global.slow_query_log='OFF';
CREATE USER plug_user IDENTIFIED WITH test_plugin_server AS 'plug_dest';
CREATE USER plug_dest IDENTIFIED BY 'plug_dest_passwd';
GRANT PROXY ON plug_dest TO plug_user;
RENAME USER plug_dest TO new_dest;

connect(con1, localhost, root,,);
connect(con2, localhost, root,,);
connect(con3, localhost, root,,);

connection con1;
SET debug_sync='mysql_grant SIGNAL ready1 WAIT_FOR go1';
SET debug_dbug='+d,mysql_grant';
send REVOKE ALL ON *.* FROM no_such_user@localhost;

connection con2;
SET debug_sync='now WAIT_FOR ready1';
SET debug_sync='fill_schema_table_from_frm SIGNAL ready2 WAIT_FOR go2';
send SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS;

connection con3;
SET debug_sync='now WAIT_FOR ready2';
SET debug_sync='activate_log_handler SIGNAL ready3 WAIT_FOR go3';
SET debug_dbug='+d,activate_log_handler';
send SET @@global.slow_query_log='ON';

connection default;
SET debug_sync='now WAIT_FOR ready3';
--error 1
--exec $MYSQL -S $MASTER_MYSOCK -u plug_user --password=plug_dest -e "SELECT 1;"

connection con1;
--error 1141
reap;
disconnect con1;

connection con2;
reap;
disconnect con2;

connection con3;
reap;
disconnect con3;

connection default;
DROP USER plug_user, new_dest;
SET debug_sync='RESET';

=== modified file 'sql/log.cc'
--- sql/log.cc	2014-08-02 19:26:16 +0000
+++ sql/log.cc	2014-09-18 15:16:51 +0000
@@ -1400,7 +1400,12 @@ bool LOGGER::activate_log_handler(THD* t
 {
   MYSQL_QUERY_LOG *file_log;
   bool res= FALSE;
+  DEBUG_SYNC(thd, "activate_log_handler");
   lock_exclusive();
+  DBUG_EXECUTE_IF("activate_log_handler",
+  {
+    debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL ready3"));
+  };);
   switch (log_type) {
   case QUERY_LOG_SLOW:
     if (!opt_slow_log)

=== modified file 'sql/sql_acl.cc'
--- sql/sql_acl.cc	2014-08-02 19:26:16 +0000
+++ sql/sql_acl.cc	2014-09-18 15:18:52 +0000
@@ -53,6 +53,7 @@
 #include "sql_array.h"

 #include "sql_plugin_compat.h"
+#include "debug_sync.h"

 bool mysql_user_table_is_in_short_password_format= false;

@@ -4142,8 +4143,13 @@ bool mysql_grant(THD *thd, const char *d
   if (!revoke_grant)
     create_new_users= test_if_create_new_users(thd);

+  DEBUG_SYNC(thd, "mysql_grant");
   /* go through users in user_list */
   mysql_rwlock_wrlock(&LOCK_grant);
+  DBUG_EXECUTE_IF("mysql_grant",
+  {
+    debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL ready1"));
+  };);
   mysql_mutex_lock(&acl_cache->lock);
   grant_version++;

@@ -9225,7 +9231,12 @@ bool acl_authenticate(THD *thd, uint con
       if (!acl_proxy_user)
       {
         if (!thd->is_error())
+        {
+          debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL go1 WAIT_FOR ready1"));
+          debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL go2"));
+          debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL go3 WAIT_FOR ready3"));
           login_failed_error(thd);
+        }
         mysql_mutex_unlock(&acl_cache->lock);
         DBUG_RETURN(1);
       }

=== modified file 'sql/sql_show.cc'
--- sql/sql_show.cc	2014-08-31 17:55:11 +0000
+++ sql/sql_show.cc	2014-09-18 15:07:47 +0000
@@ -4244,6 +4244,7 @@ static int fill_schema_table_from_frm(TH
   key_length= create_table_def_key(thd, key, &table_list, 0);
   hash_value= my_calc_hash(&table_def_cache, (uchar*) key, key_length);
   mysql_mutex_lock(&LOCK_open);
+  DEBUG_SYNC(thd, "fill_schema_table_from_frm");
   share= get_table_share(thd, &table_list, key,
                          key_length, OPEN_VIEW, &not_used, hash_value);
   if (!share)