Merge from 5.0

******
manual merge 5.0-bugteam --> 5.1-bugteam (bug 38816)

13 files changed, 110 insertions, 119 deletions

diff --git a/sql/event_data_objects.cc b/sql/event_data_objects.cc
index 0eba357b632..dba32cac6b2 100644
--- a/sql/event_data_objects.cc
+++ b/sql/event_data_objects.cc
@@ -1430,13 +1430,7 @@ Event_job_data::execute(THD *thd, bool drop)
   thd->variables.sql_mode= sql_mode;
   thd->variables.time_zone= time_zone;
 
-  /*
-    Peculiar initialization order is a crutch to avoid races in SHOW
-    PROCESSLIST which reads thd->{query/query_length} without a mutex.
-  */
-  thd->query_length= 0;
-  thd->query= sp_sql.c_ptr_safe();
-  thd->query_length= sp_sql.length();
+  thd->set_query(sp_sql.c_ptr_safe(), sp_sql.length());
 
   {
     Parser_state parser_state(thd, thd->query, thd->query_length);
@@ -1497,13 +1491,8 @@ end_no_lex_start:
     else
     {
       ulong saved_master_access;
-      /*
-        Peculiar initialization order is a crutch to avoid races in SHOW
-        PROCESSLIST which reads thd->{query/query_length} without a mutex.
-      */
-      thd->query_length= 0;
-      thd->query= sp_sql.c_ptr_safe();
-      thd->query_length= sp_sql.length();
+
+      thd->set_query(sp_sql.c_ptr_safe(), sp_sql.length());
 
       /*
         NOTE: even if we run in read-only mode, we should be able to lock
@@ -1528,8 +1517,7 @@ end_no_lex_start:
   thd->end_statement();
   thd->cleanup_after_query();
   /* Avoid races with SHOW PROCESSLIST */
-  thd->query_length= 0;
-  thd->query= NULL;
+  thd->set_query(NULL, 0);
 
   DBUG_PRINT("info", ("EXECUTED %s.%s  ret: %d", dbname.str, name.str, ret));
 
diff --git a/sql/event_scheduler.cc b/sql/event_scheduler.cc
index d9d010783e8..78aad2b4c3d 100644
--- a/sql/event_scheduler.cc
+++ b/sql/event_scheduler.cc
@@ -625,13 +625,13 @@ Event_scheduler::stop()
     DBUG_PRINT("info", ("Scheduler thread has id %lu",
                         scheduler_thd->thread_id));
     /* Lock from delete */
-    pthread_mutex_lock(&scheduler_thd->LOCK_delete);
+    pthread_mutex_lock(&scheduler_thd->LOCK_thd_data);
     /* This will wake up the thread if it waits on Queue's conditional */
     sql_print_information("Event Scheduler: Killing the scheduler thread, "
                           "thread id %lu",
                           scheduler_thd->thread_id);
     scheduler_thd->awake(THD::KILL_CONNECTION);
-    pthread_mutex_unlock(&scheduler_thd->LOCK_delete);
+    pthread_mutex_unlock(&scheduler_thd->LOCK_thd_data);
 
     /* thd could be 0x0, when shutting down */
     sql_print_information("Event Scheduler: "
diff --git a/sql/ha_ndbcluster_binlog.cc b/sql/ha_ndbcluster_binlog.cc
index f705af8bf47..a3adbe4a952 100644
--- a/sql/ha_ndbcluster_binlog.cc
+++ b/sql/ha_ndbcluster_binlog.cc
@@ -253,8 +253,7 @@ static void run_query(THD *thd, char *buf, char *end,
   const char* found_semicolon= NULL;
 
   bzero((char*) &thd->net, sizeof(NET));
-  thd->query_length= end - buf;
-  thd->query= buf;
+  thd->set_query(buf, (uint) (end - buf));
   thd->variables.pseudo_thread_id= thread_id;
   thd->transaction.stmt.modified_non_trans_table= FALSE;
   if (disable_binlog)
@@ -297,8 +296,7 @@ static void run_query(THD *thd, char *buf, char *end,
   thd->main_da.reset_diagnostics_area();
 
   thd->options= save_thd_options;
-  thd->query_length= save_thd_query_length;
-  thd->query= save_thd_query;
+  thd->set_query(save_thd_query, save_thd_query_length);
   thd->variables.pseudo_thread_id= save_thread_id;
   thd->status_var= save_thd_status_var;
   thd->transaction.all= save_thd_transaction_all;
diff --git a/sql/log_event.cc b/sql/log_event.cc
index 5f77ab3dcc4..e7cbbaba38e 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -3025,8 +3025,7 @@ int Query_log_event::do_apply_event(Relay_log_info const *rli,
       rpl_filter->db_ok(thd->db))
   {
     thd->set_time((time_t)when);
-    thd->query_length= q_len_arg;
-    thd->query= (char*)query_arg;
+    thd->set_query((char*)query_arg, q_len_arg);
     VOID(pthread_mutex_lock(&LOCK_thread_count));
     thd->query_id = next_query_id();
     VOID(pthread_mutex_unlock(&LOCK_thread_count));
@@ -3231,7 +3230,6 @@ Default database: '%s'. Query: '%s'",
   } /* End of if (db_ok(... */
 
 end:
-  VOID(pthread_mutex_lock(&LOCK_thread_count));
   /*
     Probably we have set thd->query, thd->db, thd->catalog to point to places
     in the data_buf of this event. Now the event is going to be deleted
@@ -3244,10 +3242,8 @@ end:
   */
   thd->catalog= 0;
   thd->set_db(NULL, 0);                 /* will free the current database */
+  thd->set_query(NULL, 0);
   DBUG_PRINT("info", ("end: query= 0"));
-  thd->query= 0;			// just to be sure
-  thd->query_length= 0;
-  VOID(pthread_mutex_unlock(&LOCK_thread_count));
   close_thread_tables(thd);      
   /*
     As a disk space optimization, future masters will not log an event for
@@ -4557,8 +4553,7 @@ int Load_log_event::do_apply_event(NET* net, Relay_log_info const *rli,
       print_query(FALSE, load_data_query, &end, (char **)&thd->lex->fname_start,
                   (char **)&thd->lex->fname_end);
       *end= 0;
-      thd->query_length= end - load_data_query;
-      thd->query= load_data_query;
+      thd->set_query(load_data_query, (uint) (end - load_data_query));
 
       if (sql_ex.opt_flags & REPLACE_FLAG)
       {
@@ -4664,12 +4659,9 @@ int Load_log_event::do_apply_event(NET* net, Relay_log_info const *rli,
 error:
   thd->net.vio = 0; 
   const char *remember_db= thd->db;
-  VOID(pthread_mutex_lock(&LOCK_thread_count));
   thd->catalog= 0;
   thd->set_db(NULL, 0);                   /* will free the current database */
-  thd->query= 0;
-  thd->query_length= 0;
-  VOID(pthread_mutex_unlock(&LOCK_thread_count));
+  thd->set_query(NULL, 0);
   close_thread_tables(thd);
 
   DBUG_EXECUTE_IF("LOAD_DATA_INFILE_has_fatal_error",
diff --git a/sql/slave.cc b/sql/slave.cc
index 83a4d8c73d1..3b64e23ece5 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -512,7 +512,7 @@ terminate_slave_thread(THD *thd,
     int error;
     DBUG_PRINT("loop", ("killing slave thread"));
 
-    pthread_mutex_lock(&thd->LOCK_delete);
+    pthread_mutex_lock(&thd->LOCK_thd_data);
 #ifndef DONT_USE_THR_ALARM
     /*
       Error codes from pthread_kill are:
@@ -523,7 +523,7 @@ terminate_slave_thread(THD *thd,
     DBUG_ASSERT(err != EINVAL);
 #endif
     thd->awake(THD::NOT_KILLED);
-    pthread_mutex_unlock(&thd->LOCK_delete);
+    pthread_mutex_unlock(&thd->LOCK_thd_data);
 
     /*
       There is a small chance that slave thread might miss the first
@@ -1250,15 +1250,13 @@ static int create_table_from_dump(THD* thd, MYSQL *mysql, const char* db,
     DBUG_RETURN(1);
   }
   thd->command = COM_TABLE_DUMP;
-  thd->query_length= packet_len;
-  /* Note that we should not set thd->query until the area is initalized */
   if (!(query = thd->strmake((char*) net->read_pos, packet_len)))
   {
     sql_print_error("create_table_from_dump: out of memory");
     my_message(ER_GET_ERRNO, "Out of memory", MYF(0));
     DBUG_RETURN(1);
   }
-  thd->query= query;
+  thd->set_query(query, packet_len);
   thd->is_slave_error = 0;
 
   bzero((char*) &tables,sizeof(tables));
@@ -2755,10 +2753,8 @@ err:
   // print the current replication position
   sql_print_information("Slave I/O thread exiting, read up to log '%s', position %s",
                   IO_RPL_LOG_NAME, llstr(mi->master_log_pos,llbuff));
-  VOID(pthread_mutex_lock(&LOCK_thread_count));
-  thd->query = thd->db = 0; // extra safety
-  thd->query_length= thd->db_length= 0;
-  VOID(pthread_mutex_unlock(&LOCK_thread_count));
+  thd->set_query(NULL, 0);
+  thd->reset_db(NULL, 0);
   if (mysql)
   {
     /*
@@ -3110,15 +3106,14 @@ the slave SQL thread with \"SLAVE START\". We stopped at log \
     must "proactively" clear playgrounds:
   */
   rli->cleanup_context(thd, 1);
-  VOID(pthread_mutex_lock(&LOCK_thread_count));
   /*
     Some extra safety, which should not been needed (normally, event deletion
     should already have done these assignments (each event which sets these
     variables is supposed to set them to 0 before terminating)).
   */
-  thd->query= thd->db= thd->catalog= 0;
-  thd->query_length= thd->db_length= 0;
-  VOID(pthread_mutex_unlock(&LOCK_thread_count));
+  thd->catalog= 0;
+  thd->set_query(NULL, 0);
+  thd->reset_db(NULL, 0);
   thd_proc_info(thd, "Waiting for slave mutex on exit");
   pthread_mutex_lock(&rli->run_lock);
   /* We need data_lock, at least to wake up any waiting master_pos_wait() */
diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 8a8a5b06cc1..018937fec2f 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -1012,8 +1012,7 @@ subst_spvars(THD *thd, sp_instr *instr, LEX_STRING *query_str)
   else
     DBUG_RETURN(TRUE);
 
-  thd->query= pbuf;
-  thd->query_length= qbuf.length();
+  thd->set_query(pbuf, qbuf.length());
 
   DBUG_RETURN(FALSE);
 }
@@ -2858,8 +2857,7 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
     }
     else
       *nextp= m_ip+1;
-    thd->query= query;
-    thd->query_length= query_length;
+    thd->set_query(query, query_length);
     thd->query_name_consts= 0;
 
     if (!thd->is_error())
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 48ddb42f0d8..54684e4987e 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -627,7 +627,7 @@ THD::THD()
 #ifdef SIGNAL_WITH_VIO_CLOSE
   active_vio = 0;
 #endif
-  pthread_mutex_init(&LOCK_delete, MY_MUTEX_INIT_FAST);
+  pthread_mutex_init(&LOCK_thd_data, MY_MUTEX_INIT_FAST);
 
   /* Variables with default values */
   proc_info="login";
@@ -911,8 +911,8 @@ THD::~THD()
   THD_CHECK_SENTRY(this);
   DBUG_ENTER("~THD()");
   /* Ensure that no one is using THD */
-  pthread_mutex_lock(&LOCK_delete);
-  pthread_mutex_unlock(&LOCK_delete);
+  pthread_mutex_lock(&LOCK_thd_data);
+  pthread_mutex_unlock(&LOCK_thd_data);
   add_to_status(&global_status_var, &status_var);
 
   /* Close connection */
@@ -939,7 +939,7 @@ THD::~THD()
   free_root(&transaction.mem_root,MYF(0));
 #endif
   mysys_var=0;					// Safety (shouldn't be needed)
-  pthread_mutex_destroy(&LOCK_delete);
+  pthread_mutex_destroy(&LOCK_thd_data);
 #ifndef DBUG_OFF
   dbug_sentry= THD_SENTRY_GONE;
 #endif  
@@ -1012,7 +1012,7 @@ void THD::awake(THD::killed_state state_to_set)
   DBUG_ENTER("THD::awake");
   DBUG_PRINT("enter", ("this: 0x%lx", (long) this));
   THD_CHECK_SENTRY(this);
-  safe_mutex_assert_owner(&LOCK_delete); 
+  safe_mutex_assert_owner(&LOCK_thd_data);
 
   killed= state_to_set;
   if (state_to_set != THD::KILL_QUERY)
@@ -1409,7 +1409,7 @@ int THD::send_explain_fields(select_result *result)
 void THD::close_active_vio()
 {
   DBUG_ENTER("close_active_vio");
-  safe_mutex_assert_owner(&LOCK_delete); 
+  safe_mutex_assert_owner(&LOCK_thd_data);
 #ifndef EMBEDDED_LIBRARY
   if (active_vio)
   {
@@ -3055,6 +3055,25 @@ void THD::restore_sub_statement_state(Sub_statement_state *backup)
 }
 
 
+void THD::set_statement(Statement *stmt)
+{
+  pthread_mutex_lock(&LOCK_thd_data);
+  Statement::set_statement(stmt);
+  pthread_mutex_unlock(&LOCK_thd_data);
+}
+
+
+/** Assign a new value to thd->query.  */
+
+void THD::set_query(char *query_arg, uint32 query_length_arg)
+{
+  pthread_mutex_lock(&LOCK_thd_data);
+  query= query_arg;
+  query_length= query_length_arg;
+  pthread_mutex_unlock(&LOCK_thd_data);
+}
+
+
 /**
   Mark transaction to rollback and mark error as fatal to a sub-statement.
 
diff --git a/sql/sql_class.h b/sql/sql_class.h
index a758d24131b..f1b56551b50 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -631,22 +631,16 @@ public:
     we need to declare it char * because all table handlers are written
     in C and need to point to it.
 
-    Note that (A) if we set query = NULL, we must at the same time set
-    query_length = 0, and protect the whole operation with the
-    LOCK_thread_count mutex. And (B) we are ONLY allowed to set query to a
-    non-NULL value if its previous value is NULL. We do not need to protect
-    operation (B) with any mutex. To avoid crashes in races, if we do not
-    know that thd->query cannot change at the moment, one should print
+    Note that if we set query = NULL, we must at the same time set
+    query_length = 0, and protect the whole operation with
+    LOCK_thd_data mutex. To avoid crashes in races, if we do not
+    know that thd->query cannot change at the moment, we should print
     thd->query like this:
-      (1) reserve the LOCK_thread_count mutex;
-      (2) check if thd->query is NULL;
-      (3) if not NULL, then print at most thd->query_length characters from
-      it. We will see the query_length field as either 0, or the right value
-      for it.
-    Assuming that the write and read of an n-bit memory field in an n-bit
-    computer is atomic, we can avoid races in the above way. 
-    This printing is needed at least in SHOW PROCESSLIST and SHOW INNODB
-    STATUS.
+      (1) reserve the LOCK_thd_data mutex;
+      (2) print or copy the value of query and query_length
+      (3) release LOCK_thd_data mutex.
+    This printing is needed at least in SHOW PROCESSLIST and SHOW
+    ENGINE INNODB STATUS.
   */
   char *query;
   uint32 query_length;                          // current query length
@@ -678,7 +672,7 @@ public:
   virtual ~Statement();
 
   /* Assign execution context (note: not all members) of given stmt to self */
-  void set_statement(Statement *stmt);
+  virtual void set_statement(Statement *stmt);
   void set_n_backup_statement(Statement *stmt, Statement *backup);
   void restore_backup_statement(Statement *stmt, Statement *backup);
   /* return class type */
@@ -1298,7 +1292,15 @@ public:
   THR_LOCK_OWNER main_lock_id;          // To use for conventional queries
   THR_LOCK_OWNER *lock_id;              // If not main_lock_id, points to
                                         // the lock_id of a cursor.
-  pthread_mutex_t LOCK_delete;		// Locked before thd is deleted
+  /**
+    Protects THD data accessed from other threads:
+    - thd->query and thd->query_length (used by SHOW ENGINE
+      INNODB STATUS and SHOW PROCESSLIST
+    - thd->mysys_var (used by KILL statement and shutdown).
+    Is locked when THD is deleted.
+  */
+  pthread_mutex_t LOCK_thd_data;
+
   /* all prepared statements and cursors of this connection */
   Statement_map stmt_map;
   /*
@@ -1890,15 +1892,15 @@ public:
 #ifdef SIGNAL_WITH_VIO_CLOSE
   inline void set_active_vio(Vio* vio)
   {
-    pthread_mutex_lock(&LOCK_delete);
+    pthread_mutex_lock(&LOCK_thd_data);
     active_vio = vio;
-    pthread_mutex_unlock(&LOCK_delete);
+    pthread_mutex_unlock(&LOCK_thd_data);
   }
   inline void clear_active_vio()
   {
-    pthread_mutex_lock(&LOCK_delete);
+    pthread_mutex_lock(&LOCK_thd_data);
     active_vio = 0;
-    pthread_mutex_unlock(&LOCK_delete);
+    pthread_mutex_unlock(&LOCK_thd_data);
   }
   void close_active_vio();
 #endif
@@ -2271,6 +2273,14 @@ public:
   */
   void pop_internal_handler();
 
+  /** Overloaded to guard query/query_length fields */
+  virtual void set_statement(Statement *stmt);
+
+  /**
+    Assign a new value to thd->query.
+    Protected with LOCK_thd_data mutex.
+  */
+  void set_query(char *query_arg, uint32 query_length_arg);
 private:
   /** The current internal error handler for this thread, or NULL. */
   Internal_error_handler *m_internal_handler;
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index 104c81ca984..7d581f8c3a9 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -1909,7 +1909,7 @@ bool delayed_get_table(THD *thd, TABLE_LIST *table_list)
       thread_count++;
       pthread_mutex_unlock(&LOCK_thread_count);
       di->thd.set_db(table_list->db, (uint) strlen(table_list->db));
-      di->thd.query= my_strdup(table_list->table_name, MYF(MY_WME));
+      di->thd.set_query(my_strdup(table_list->table_name, MYF(MY_WME)), 0);
       if (di->thd.db == NULL || di->thd.query == NULL)
       {
         /* The error is reported */
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 542ce992537..88699ea6979 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -457,6 +457,7 @@ pthread_handler_t handle_bootstrap(void *arg)
   thd->init_for_queries();
   while (fgets(buff, thd->net.max_packet, file))
   {
+    char *query;
     /* strlen() can't be deleted because fgets() doesn't return length */
     ulong length= (ulong) strlen(buff);
     while (buff[length-1] != '\n' && !feof(file))
@@ -489,11 +490,10 @@ pthread_handler_t handle_bootstrap(void *arg)
     if (strncmp(buff, STRING_WITH_LEN("delimiter")) == 0)
       continue;
 
-    thd->query_length=length;
-    thd->query= (char*) thd->memdup_w_gap(buff, length+1, 
-                                          thd->db_length+1+
-                                          QUERY_CACHE_FLAGS_SIZE);
-    thd->query[length] = '\0';
+    query= (char *) thd->memdup_w_gap(buff, length + 1,
+                                      thd->db_length + 1 +
+                                      QUERY_CACHE_FLAGS_SIZE);
+    thd->set_query(query, length);
     DBUG_PRINT("query",("%-.4096s",thd->query));
 #if defined(ENABLED_PROFILING) && defined(COMMUNITY_SERVER)
     thd->profiling.start_new_query();
@@ -658,8 +658,7 @@ int mysql_table_dump(THD *thd, LEX_STRING *db, char *tbl_name)
   if (check_one_table_access(thd, SELECT_ACL, table_list))
     goto err;
   thd->free_list = 0;
-  thd->query_length=(uint) strlen(tbl_name);
-  thd->query = tbl_name;
+  thd->set_query(tbl_name, (uint) strlen(tbl_name));
   if ((error = mysqld_dump_create_info(thd, table_list, -1)))
   {
     my_error(ER_GET_ERRNO, MYF(0), my_errno);
@@ -1239,9 +1238,8 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       thd->profiling.set_query_source(beginning_of_next_stmt, length);
 #endif
 
+      thd->set_query(beginning_of_next_stmt, length);
       VOID(pthread_mutex_lock(&LOCK_thread_count));
-      thd->query_length= length;
-      thd->query= beginning_of_next_stmt;
       /*
         Count each statement from the client.
       */
@@ -1294,9 +1292,10 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
         table_list.schema_table= schema_table;
     }
 
-    thd->query_length= (uint) (packet_end - packet); // Don't count end \0
-    if (!(thd->query=fields= (char*) thd->memdup(packet,thd->query_length+1)))
+    uint query_length= (uint) (packet_end - packet); // Don't count end \0
+    if (!(fields= (char *) thd->memdup(packet, query_length + 1)))
       break;
+    thd->set_query(fields, query_length);
     general_log_print(thd, command, "%s %s", table_list.table_name, fields);
     if (lower_case_table_names)
       my_casedn_str(files_charset_info, table_list.table_name);
@@ -1589,13 +1588,12 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   log_slow_statement(thd);
 
   thd_proc_info(thd, "cleaning up");
-  VOID(pthread_mutex_lock(&LOCK_thread_count)); // For process list
-  thd_proc_info(thd, 0);
+  thd->set_query(NULL, 0);
   thd->command=COM_SLEEP;
-  thd->query=0;
-  thd->query_length=0;
+  VOID(pthread_mutex_lock(&LOCK_thread_count)); // For process list
   thread_running--;
   VOID(pthread_mutex_unlock(&LOCK_thread_count));
+  thd_proc_info(thd, 0);
   thd->packet.shrink(thd->variables.net_buffer_length);	// Reclaim some memory
   free_root(thd->mem_root,MYF(MY_KEEP_PREALLOC));
   DBUG_RETURN(error);
@@ -1788,6 +1786,7 @@ int prepare_schema_table(THD *thd, LEX *lex, Table_ident *table_ident,
 
 bool alloc_query(THD *thd, const char *packet, uint packet_length)
 {
+  char *query;
   /* Remove garbage at start and end of query */
   while (packet_length > 0 && my_isspace(thd->charset(), packet[0]))
   {
@@ -1802,14 +1801,13 @@ bool alloc_query(THD *thd, const char *packet, uint packet_length)
     packet_length--;
   }
   /* We must allocate some extra memory for query cache */
-  thd->query_length= 0;                        // Extra safety: Avoid races
-  if (!(thd->query= (char*) thd->memdup_w_gap((uchar*) (packet),
-					      packet_length,
-					      thd->db_length+ 1 +
-					      QUERY_CACHE_FLAGS_SIZE)))
-    return TRUE;
-  thd->query[packet_length]=0;
-  thd->query_length= packet_length;
+  if (! (query= (char*) thd->memdup_w_gap(packet,
+                                          packet_length,
+                                          1 + thd->db_length +
+                                          QUERY_CACHE_FLAGS_SIZE)))
+      return TRUE;
+  query[packet_length]= '\0';
+  thd->set_query(query, packet_length);
 
   /* Reclaim some memory */
   thd->packet.shrink(thd->variables.net_buffer_length);
@@ -6950,7 +6948,7 @@ uint kill_one_thread(THD *thd, ulong id, bool only_kill_query)
       continue;
     if (tmp->thread_id == id)
     {
-      pthread_mutex_lock(&tmp->LOCK_delete);	// Lock from delete
+      pthread_mutex_lock(&tmp->LOCK_thd_data);	// Lock from delete
       break;
     }
   }
@@ -6983,7 +6981,7 @@ uint kill_one_thread(THD *thd, ulong id, bool only_kill_query)
     }
     else
       error=ER_KILL_DENIED_ERROR;
-    pthread_mutex_unlock(&tmp->LOCK_delete);
+    pthread_mutex_unlock(&tmp->LOCK_thd_data);
   }
   DBUG_PRINT("exit", ("%d", error));
   DBUG_RETURN(error);
diff --git a/sql/sql_repl.cc b/sql/sql_repl.cc
index 476c8aaaefb..0ec8d91214c 100644
--- a/sql/sql_repl.cc
+++ b/sql/sql_repl.cc
@@ -1102,7 +1102,7 @@ void kill_zombie_dump_threads(uint32 slave_server_id)
     if (tmp->command == COM_BINLOG_DUMP &&
        tmp->server_id == slave_server_id)
     {
-      pthread_mutex_lock(&tmp->LOCK_delete);	// Lock from delete
+      pthread_mutex_lock(&tmp->LOCK_thd_data);	// Lock from delete
       break;
     }
   }
@@ -1115,7 +1115,7 @@ void kill_zombie_dump_threads(uint32 slave_server_id)
       again. We just to do kill the thread ourselves.
     */
     tmp->awake(THD::KILL_QUERY);
-    pthread_mutex_unlock(&tmp->LOCK_delete);
+    pthread_mutex_unlock(&tmp->LOCK_thd_data);
   }
 }
 
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index a1f6798244e..35dbb64dfef 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -1768,16 +1768,14 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
 
         thd_info->start_time= tmp->start_time;
         thd_info->query=0;
+        /* Lock THD mutex that protects its data when looking at it. */
+        pthread_mutex_lock(&tmp->LOCK_thd_data);
         if (tmp->query)
         {
-	  /* 
-            query_length is always set to 0 when we set query = NULL; see
-	    the comment in sql_class.h why this prevents crashes in possible
-            races with query_length
-          */
           uint length= min(max_query_length, tmp->query_length);
           thd_info->query=(char*) thd->strmake(tmp->query,length);
         }
+        pthread_mutex_unlock(&tmp->LOCK_thd_data);
         thread_infos.append(thd_info);
       }
     }
diff --git a/storage/myisam/ha_myisam.cc b/storage/myisam/ha_myisam.cc
index d0e5f5a5c88..5198e685817 100644
--- a/storage/myisam/ha_myisam.cc
+++ b/storage/myisam/ha_myisam.cc
@@ -1612,10 +1612,8 @@ bool ha_myisam::check_and_repair(THD *thd)
 
   old_query= thd->query;
   old_query_length= thd->query_length;
-  pthread_mutex_lock(&LOCK_thread_count);
-  thd->query=        table->s->table_name.str;
-  thd->query_length= (uint) table->s->table_name.length;
-  pthread_mutex_unlock(&LOCK_thread_count);
+  thd->set_query(table->s->table_name.str,
+                 (uint) table->s->table_name.length);
 
   if ((marked_crashed= mi_is_crashed(file)) || check(thd, &check_opt))
   {
@@ -1628,10 +1626,7 @@ bool ha_myisam::check_and_repair(THD *thd)
     if (repair(thd, &check_opt))
       error=1;
   }
-  pthread_mutex_lock(&LOCK_thread_count);
-  thd->query= old_query;
-  thd->query_length= old_query_length;
-  pthread_mutex_unlock(&LOCK_thread_count);
+  thd->set_query(old_query, old_query_length);
   DBUG_RETURN(error);
 }