Bug#17283409 4-WAY DEADLOCK: ZOMBIES, PURGING BINLOGS,

SHOW PROCESSLIST, SHOW BINLOGS

Problem:  A deadlock was occurring when 4 threads were
involved in acquiring locks in the following way
Thread 1: Dump thread ( Slave is reconnecting, so on
              Master, a new dump thread is trying kill
              zombie dump threads. It acquired thread's
              LOCK_thd_data and it is about to acquire
              mysys_var->current_mutex ( which LOCK_log)
Thread 2: Application thread is executing show binlogs and
               acquired LOCK_log and it is about to acquire
               LOCK_index.
Thread 3: Application thread is executing Purge binary logs
               and acquired LOCK_index and it is about to
               acquire LOCK_thread_count.
Thread 4: Application thread is executing show processlist
               and acquired LOCK_thread_count and it is
               about to acquire zombie dump thread's
               LOCK_thd_data.
Deadlock Cycle:
     Thread 1 -> Thread 2 -> Thread 3-> Thread 4 ->Thread 1

The same above deadlock was observed even when thread 4 is
executing 'SELECT * FROM information_schema.processlist' command and
acquired LOCK_thread_count and it is about to acquire zombie
dump thread's LOCK_thd_data.

Analysis:
There are four locks involved in the deadlock.  LOCK_log,
LOCK_thread_count, LOCK_index and LOCK_thd_data.
LOCK_log, LOCK_thread_count, LOCK_index are global mutexes
where as LOCK_thd_data is local to a thread.
We can divide these four locks in two groups.
Group 1 consists of LOCK_log and LOCK_index and the order
should be LOCK_log followed by LOCK_index.
Group 2 consists of other two mutexes
LOCK_thread_count, LOCK_thd_data and the order should
be LOCK_thread_count followed by LOCK_thd_data.
Unfortunately, there is no specific predefined lock order defined
to follow in the MySQL system when it comes to locks across these
two groups. In the above problematic example,
there is no problem in the way we are acquiring the locks
if you see each thread individually.
But If you combine all 4 threads, they end up in a deadlock.

Fix: 
Since everything seems to be fine in the way threads are taking locks,
In this patch We are changing the duration of the locks in Thread 4
to break the deadlock. i.e., before the patch, Thread 4
('show processlist' command) mysqld_list_processes()
function acquires LOCK_thread_count for the complete duration
of the function and it also acquires/releases
each thread's LOCK_thd_data.

LOCK_thread_count is used to protect addition and
deletion of threads in global threads list. While show
process list is looping through all the existing threads,
it will be a problem if a thread is exited but there is no problem
if a new thread is added to the system. Hence a new mutex is
introduced "LOCK_thd_remove" which will protect deletion
of a thread from global threads list. All threads which are
getting exited should acquire LOCK_thd_remove
followed by LOCK_thread_count. (It should take LOCK_thread_count
also because other places of the code still thinks that exit thread
is protected with LOCK_thread_count. In this fix, we are changing
only 'show process list' query logic )
(Eg: unlink_thd logic will be protected with
LOCK_thd_remove).

Logic of mysqld_list_processes(or file_schema_processlist)
will now be protected with 'LOCK_thd_remove' instead of
'LOCK_thread_count'.

Now the new locking order after this patch is:
LOCK_thd_remove -> LOCK_thd_data -> LOCK_log ->
LOCK_index -> LOCK_thread_count

10 files changed, 104 insertions, 32 deletions

diff --git a/sql/event_scheduler.cc b/sql/event_scheduler.cc
index 52eae66b603..2c397f15357 100644
--- a/sql/event_scheduler.cc
+++ b/sql/event_scheduler.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2006, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -22,6 +22,7 @@
 #include "event_db_repository.h"
 #include "sql_connect.h"         // init_new_connection_handler_thread
 #include "sql_acl.h"             // SUPER_ACL
+extern void delete_thd(THD *);   // Used in deinit_event_thread()
 
 /**
   @addtogroup Event_Scheduler
@@ -156,12 +157,13 @@ deinit_event_thread(THD *thd)
   DBUG_ASSERT(thd->net.buff != 0);
   net_end(&thd->net);
   DBUG_PRINT("exit", ("Event thread finishing"));
+  mysql_mutex_lock(&LOCK_thd_remove);
   mysql_mutex_lock(&LOCK_thread_count);
-  thread_count--;
   dec_thread_running();
-  delete thd;
+  delete_thd(thd);
   mysql_cond_broadcast(&COND_thread_count);
   mysql_mutex_unlock(&LOCK_thread_count);
+  mysql_mutex_unlock(&LOCK_thd_remove);
 }
 
 
diff --git a/sql/log.cc b/sql/log.cc
index b318780ea41..7327015deb5 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -3428,6 +3428,13 @@ bool MYSQL_BIN_LOG::reset_logs(THD* thd)
   ha_reset_logs(thd);
 
   /*
+    We need to get both locks to be sure that no one is trying to
+    write to the index log file.
+  */
+  mysql_mutex_lock(&LOCK_log);
+  mysql_mutex_lock(&LOCK_index);
+
+  /*
     The following mutex is needed to ensure that no threads call
     'delete thd' as we would then risk missing a 'rollback' from this
     thread. If the transaction involved MyISAM tables, it should go
@@ -3435,13 +3442,6 @@ bool MYSQL_BIN_LOG::reset_logs(THD* thd)
   */
   mysql_mutex_lock(&LOCK_thread_count);
 
-  /*
-    We need to get both locks to be sure that no one is trying to
-    write to the index log file.
-  */
-  mysql_mutex_lock(&LOCK_log);
-  mysql_mutex_lock(&LOCK_index);
-
   /* Save variables so that we can reopen the log */
   save_name=name;
   name=0;					// Protect against free
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index b61e64e627b..1489e3cdc31 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -642,7 +642,7 @@ SHOW_COMP_OPTION have_profiling;
 pthread_key(MEM_ROOT**,THR_MALLOC);
 pthread_key(THD*, THR_THD);
 mysql_mutex_t LOCK_thread_created;
-mysql_mutex_t LOCK_thread_count;
+mysql_mutex_t LOCK_thread_count, LOCK_thd_remove;
 mysql_mutex_t
   LOCK_status, LOCK_error_log, LOCK_uuid_generator,
   LOCK_delayed_insert, LOCK_delayed_status, LOCK_delayed_create,
@@ -1607,6 +1607,7 @@ static void clean_up_mutexes()
   mysql_mutex_destroy(&LOCK_prepared_stmt_count);
   mysql_mutex_destroy(&LOCK_error_messages);
   mysql_cond_destroy(&COND_thread_count);
+  mysql_mutex_destroy(&LOCK_thd_remove);
   mysql_cond_destroy(&COND_thread_cache);
   mysql_cond_destroy(&COND_flush_thread_cache);
   mysql_cond_destroy(&COND_manager);
@@ -2160,6 +2161,8 @@ void dec_connection_count()
 
 void delete_thd(THD *thd)
 {
+  mysql_mutex_assert_owner(&LOCK_thread_count);
+  mysql_mutex_assert_owner(&LOCK_thd_remove);
   thread_count--;
   delete thd;
 }
@@ -2173,7 +2176,7 @@ void delete_thd(THD *thd)
     thd		 Thread handler
 
   NOTES
-    LOCK_thread_count is locked and left locked
+    LOCK_thread_count, LOCK_thd_remove are locked and left locked
 */
 
 void unlink_thd(THD *thd)
@@ -2183,6 +2186,7 @@ void unlink_thd(THD *thd)
 
   thd_cleanup(thd);
   dec_connection_count();
+  mysql_mutex_lock(&LOCK_thd_remove);
   mysql_mutex_lock(&LOCK_thread_count);
   /*
     Used by binlog_reset_master.  It would be cleaner to use
@@ -2295,6 +2299,7 @@ bool one_thread_per_connection_end(THD *thd, bool put_in_cache)
 {
   DBUG_ENTER("one_thread_per_connection_end");
   unlink_thd(thd);
+  mysql_mutex_unlock(&LOCK_thd_remove);
   if (put_in_cache)
     put_in_cache= cache_thread();
   mysql_mutex_unlock(&LOCK_thread_count);
@@ -3589,6 +3594,8 @@ static int init_thread_environment()
   mysql_mutex_init(key_LOCK_thread_created, &LOCK_thread_created, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_thread_count, &LOCK_thread_count, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_status, &LOCK_status, MY_MUTEX_INIT_FAST);
+  mysql_mutex_init(key_LOCK_thd_remove,
+                   &LOCK_thd_remove, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_delayed_insert,
                    &LOCK_delayed_insert, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_delayed_status,
@@ -5080,9 +5087,11 @@ void create_thread_to_handle_connection(THD *thd)
                   ER_THD(thd, ER_CANT_CREATE_THREAD), error);
       net_send_error(thd, ER_CANT_CREATE_THREAD, error_message_buff, NULL);
       close_connection(thd);
+      mysql_mutex_lock(&LOCK_thd_remove);
       mysql_mutex_lock(&LOCK_thread_count);
       delete thd;
       mysql_mutex_unlock(&LOCK_thread_count);
+      mysql_mutex_unlock(&LOCK_thd_remove);
       return;
       /* purecov: end */
     }
@@ -7873,6 +7882,7 @@ PSI_mutex_key key_BINLOG_LOCK_index, key_BINLOG_LOCK_prep_xids,
   key_structure_guard_mutex, key_TABLE_SHARE_LOCK_ha_data,
   key_LOCK_error_messages, key_LOG_INFO_lock, key_LOCK_thread_count,
   key_PARTITION_LOCK_auto_inc;
+PSI_mutex_key key_LOCK_thd_remove;
 PSI_mutex_key key_RELAYLOG_LOCK_index;
 PSI_mutex_key key_LOCK_thread_created;
 
@@ -7928,7 +7938,8 @@ static PSI_mutex_info all_server_mutexes[]=
   { &key_LOG_INFO_lock, "LOG_INFO::lock", 0},
   { &key_LOCK_thread_count, "LOCK_thread_count", PSI_FLAG_GLOBAL},
   { &key_PARTITION_LOCK_auto_inc, "HA_DATA_PARTITION::LOCK_auto_inc", 0},
-  { &key_LOCK_thread_created, "LOCK_thread_created", PSI_FLAG_GLOBAL }
+  { &key_LOCK_thread_created, "LOCK_thread_created", PSI_FLAG_GLOBAL },
+  { &key_LOCK_thd_remove, "LOCK_thd_remove", PSI_FLAG_GLOBAL}
 };
 
 PSI_rwlock_key key_rwlock_LOCK_grant, key_rwlock_LOCK_logger,
diff --git a/sql/mysqld.h b/sql/mysqld.h
index f500a0abf3f..bd93264d50d 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2006, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -252,7 +252,8 @@ extern PSI_mutex_key key_BINLOG_LOCK_index, key_BINLOG_LOCK_prep_xids,
   key_relay_log_info_log_space_lock, key_relay_log_info_run_lock,
   key_relay_log_info_sleep_lock,
   key_structure_guard_mutex, key_TABLE_SHARE_LOCK_ha_data,
-  key_LOCK_error_messages, key_LOCK_thread_count, key_PARTITION_LOCK_auto_inc;
+  key_LOCK_error_messages, key_LOCK_thread_count, key_PARTITION_LOCK_auto_inc,
+  key_LOCK_thd_remove;
 extern PSI_mutex_key key_RELAYLOG_LOCK_index;
 
 extern PSI_rwlock_key key_rwlock_LOCK_grant, key_rwlock_LOCK_logger,
@@ -346,6 +347,7 @@ extern mysql_mutex_t
        LOCK_global_system_variables, LOCK_user_conn,
        LOCK_prepared_stmt_count, LOCK_error_messages, LOCK_connection_count;
 extern MYSQL_PLUGIN_IMPORT mysql_mutex_t LOCK_thread_count;
+extern MYSQL_PLUGIN_IMPORT mysql_mutex_t LOCK_thd_remove;
 #ifdef HAVE_OPENSSL
 extern mysql_mutex_t LOCK_des_key_file;
 #endif
diff --git a/sql/scheduler.cc b/sql/scheduler.cc
index a2abc7c14bf..fa2c43c3b65 100644
--- a/sql/scheduler.cc
+++ b/sql/scheduler.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2007, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -36,6 +36,7 @@ static bool no_threads_end(THD *thd, bool put_in_cache)
 {
   unlink_thd(thd);
   mysql_mutex_unlock(&LOCK_thread_count);
+  mysql_mutex_unlock(&LOCK_thd_remove);
   return 1;                                     // Abort handle_one_connection
 }
 
diff --git a/sql/slave.cc b/sql/slave.cc
index 0e23b1af606..23460c1af63 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -3119,10 +3119,12 @@ err:
   change_rpl_status(RPL_ACTIVE_SLAVE,RPL_IDLE_SLAVE);
   DBUG_ASSERT(thd->net.buff != 0);
   net_end(&thd->net); // destructor will not free it, because net.vio is 0
+  mysql_mutex_lock(&LOCK_thd_remove);
   mysql_mutex_lock(&LOCK_thread_count);
   THD_CHECK_SENTRY(thd);
   delete thd;
   mysql_mutex_unlock(&LOCK_thread_count);
+  mysql_mutex_unlock(&LOCK_thd_remove);
   mi->abort_slave= 0;
   mi->slave_running= 0;
   mi->io_thd= 0;
@@ -3518,10 +3520,12 @@ the slave SQL thread with \"SLAVE START\". We stopped at log \
   THD_CHECK_SENTRY(thd);
   rli->sql_thd= 0;
   set_thd_in_use_temporary_tables(rli);  // (re)set sql_thd in use for saved temp tables
+  mysql_mutex_lock(&LOCK_thd_remove);
   mysql_mutex_lock(&LOCK_thread_count);
   THD_CHECK_SENTRY(thd);
   delete thd;
   mysql_mutex_unlock(&LOCK_thread_count);
+  mysql_mutex_unlock(&LOCK_thd_remove);
  /*
   Note: the order of the broadcast and unlock calls below (first broadcast, then unlock)
   is important. Otherwise a killer_thread can execute between the calls and
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 93f1d8eb3bb..136c6012514 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -333,6 +333,26 @@ void thd_unlock_thread_count(THD *)
 }
 
 /**
+  Lock thread removal mutex
+
+  @param thd                       THD object
+*/
+void thd_lock_thread_remove(THD *)
+{
+  mysql_mutex_lock(&LOCK_thd_remove);
+}
+
+/**
+  Unlock thread removal mutex
+
+  @param thd                       THD object
+*/
+void thd_unlock_thread_remove(THD *)
+{
+  mysql_mutex_unlock(&LOCK_thd_remove);
+}
+
+/**
   Close the socket used by this connection
 
   @param thd                THD object
@@ -1561,6 +1581,13 @@ void THD::awake(THD::killed_state state_to_set)
     */
     if (mysys_var->current_cond && mysys_var->current_mutex)
     {
+      DBUG_EXECUTE_IF("before_dump_thread_acquires_current_mutex",
+                      {
+                      const char act[]=
+                      "now signal dump_thread_signal wait_for go";
+                      DBUG_ASSERT(!debug_sync_set_action(current_thd,
+                                                         STRING_WITH_LEN(act)));
+                      };);
       mysql_mutex_lock(mysys_var->current_mutex);
       mysql_cond_broadcast(mysys_var->current_cond);
       mysql_mutex_unlock(mysys_var->current_mutex);
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index 0f432779305..d6a83b9c35e 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1933,6 +1933,7 @@ public:
       close_thread_tables(&thd);
       thd.mdl_context.release_transactional_locks();
     }
+    mysql_mutex_lock(&LOCK_thd_remove);
     mysql_mutex_lock(&LOCK_thread_count);
     mysql_mutex_destroy(&mutex);
     mysql_cond_destroy(&cond);
@@ -1944,6 +1945,7 @@ public:
     thread_count--;
     delayed_insert_threads--;
     mysql_mutex_unlock(&LOCK_thread_count);
+    mysql_mutex_unlock(&LOCK_thd_remove);
     mysql_cond_broadcast(&COND_thread_count); /* Tell main we are ready */
   }
 
diff --git a/sql/sql_repl.cc b/sql/sql_repl.cc
index ec1ef72cd73..343e128af7a 100644
--- a/sql/sql_repl.cc
+++ b/sql/sql_repl.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -248,7 +248,7 @@ bool log_in_use(const char* log_name)
   size_t log_name_len = strlen(log_name) + 1;
   THD *tmp;
   bool result = 0;
-
+  DEBUG_SYNC(current_thd,"purge_logs_after_lock_index_before_thread_count");
   mysql_mutex_lock(&LOCK_thread_count);
   I_List_iterator<THD> it(threads);
 
@@ -1965,6 +1965,7 @@ bool show_binlogs(THD* thd)
     DBUG_RETURN(TRUE);
   
   mysql_mutex_lock(mysql_bin_log.get_log_lock());
+  DEBUG_SYNC(thd, "show_binlogs_after_lock_log_before_lock_index");
   mysql_bin_log.lock_index();
   index_file=mysql_bin_log.get_index_file();
   
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index ac63b2aaff9..f02ea6bead7 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -1814,13 +1814,23 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
     DBUG_VOID_RETURN;
 
-  mysql_mutex_lock(&LOCK_thread_count); // For unlink from list
+
   if (!thd->killed)
   {
+    /*
+      Acquire only LOCK_thd_remove and not LOCK_thread_count.
+      i.e., we allow new threads to be added to the list while processing
+      the list but we will not allow deletions from the list (Note that unlink
+      a thread is protected by both LOCK_thd_remove and LOCK_thread_count
+      mutexes).
+    */
+    mysql_mutex_lock(&LOCK_thd_remove);
     I_List_iterator<THD> it(threads);
     THD *tmp;
+    DEBUG_SYNC(thd,"before_one_element_read_from_threads_iterator");
     while ((tmp=it++))
     {
+      DEBUG_SYNC(thd,"after_one_element_read_from_threads_iterator");
       Security_context *tmp_sctx= tmp->security_ctx;
       struct st_my_thread_var *mysys_var;
       if ((tmp->vio_ok() || tmp->system_thread) &&
@@ -1845,6 +1855,11 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
                                       tmp_sctx->get_host()->length() ?
                                       tmp_sctx->get_host()->ptr() : "");
         thd_info->command=(int) tmp->command;
+        DBUG_EXECUTE_IF("processlist_acquiring_dump_threads_LOCK_thd_data",
+                        {
+                         if (tmp->command == COM_BINLOG_DUMP)
+                           DEBUG_SYNC(thd, "processlist_after_LOCK_thd_count_before_LOCK_thd_data");
+                        });
         mysql_mutex_lock(&tmp->LOCK_thd_data);
         if ((thd_info->db= tmp->db))             // Safe test
           thd_info->db= thd->strdup(thd_info->db);
@@ -1869,8 +1884,8 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
         thread_infos.append(thd_info);
       }
     }
+    mysql_mutex_unlock(&LOCK_thd_remove);
   }
-  mysql_mutex_unlock(&LOCK_thread_count);
 
   thread_info *thd_info;
   time_t now= my_time(0);
@@ -1910,10 +1925,15 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
   user= thd->security_ctx->master_access & PROCESS_ACL ?
         NullS : thd->security_ctx->priv_user;
 
-  mysql_mutex_lock(&LOCK_thread_count);
-
   if (!thd->killed)
   {
+    /*
+      Acquire only LOCK_thd_remove and not LOCK_thread_count.
+      i.e., we allow new threads to be added to the list while processing
+      the list but we will not allow deletions from the list (Note that unlink
+      thread is also protected with LOCK_thd_remove mutex).
+    */
+    mysql_mutex_lock(&LOCK_thd_remove);
     I_List_iterator<THD> it(threads);
     THD* tmp;
 
@@ -1946,7 +1966,13 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
       else
         table->field[2]->store(tmp_sctx->host_or_ip,
                                strlen(tmp_sctx->host_or_ip), cs);
+      DBUG_EXECUTE_IF("processlist_acquiring_dump_threads_LOCK_thd_data",
+                      {
+                       if (tmp->command == COM_BINLOG_DUMP)
+                         DEBUG_SYNC(thd, "processlist_after_LOCK_thd_count_before_LOCK_thd_data");
+                      });
       /* DB */
+      /* Lock THD mutex that protects its data when looking at it. */
       mysql_mutex_lock(&tmp->LOCK_thd_data);
       if ((db= tmp->db))
       {
@@ -1974,11 +2000,8 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
 
       if (mysys_var)
         mysql_mutex_unlock(&mysys_var->mutex);
-      mysql_mutex_unlock(&tmp->LOCK_thd_data);
 
       /* INFO */
-      /* Lock THD mutex that protects its data when looking at it. */
-      mysql_mutex_lock(&tmp->LOCK_thd_data);
       if (tmp->query())
       {
         table->field[7]->store(tmp->query(),
@@ -1990,13 +2013,12 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond)
 
       if (schema_table_store_record(thd, table))
       {
-        mysql_mutex_unlock(&LOCK_thread_count);
+        mysql_mutex_unlock(&LOCK_thd_remove);
         DBUG_RETURN(1);
       }
     }
+    mysql_mutex_unlock(&LOCK_thd_remove);
   }
-
-  mysql_mutex_unlock(&LOCK_thread_count);
   DBUG_RETURN(0);
 }