1 /* Copyright (c) 2012, 2014 Oracle and/or its affiliates. All rights reserved. 2 3 This program is free software; you can redistribute it and/or modify 4 it under the terms of the GNU General Public License, version 2.0, 5 as published by the Free Software Foundation. 6 7 This program is also distributed with certain software (including 8 but not limited to OpenSSL) that is licensed under separate terms, 9 as designated in a particular file or component or in included license 10 documentation. The authors of MySQL hereby grant you an additional 11 permission to link the program and your derivative works with the 12 separately licensed software that they have included with MySQL. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License, version 2.0, for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program; if not, write to the Free Software 21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ 22 23 #ifndef GLOBAL_THREADS_INCLUDED 24 #define GLOBAL_THREADS_INCLUDED 25 26 #include <my_global.h> 27 #include <my_pthread.h> 28 #include <set> 29 30 class THD; 31 32 extern mysql_mutex_t LOCK_thread_count; 33 extern mysql_mutex_t LOCK_thd_remove; 34 extern mysql_cond_t COND_thread_count; 35 36 /** 37 We maintain a set of all registered threads. 38 We provide accessors (global_thread_list_begin, global_thread_list_end) 39 to iterate over all threads. There is no guarantee on the order of THDs 40 when iterating. The caller of these two accessors is expected to 41 hold lock on LOCK_thread_count mutex before calling these accessors inorder 42 to make sure that there are no new threads are added to the system while 43 processing this thread list. 44 45 We also provide mutators for inserting, and removing an element: 46 > add_global_thread() inserts a THD into the set, and increments the counter. 47 The caller of this function is expected to hold lock on LOCK_thread_count 48 mutex before calling this function to avoid any parallel operations 49 happening on the set. 50 > remove_global_thread() removes a THD from the set, and decrements the counter. 51 This function acquires lock on LOCK_thd_remove followed by lock on 52 LOCK_thread_count. At the end of the function, it releases both the 53 locks. remove_global_thread() also broadcasts COND_thread_count. 54 55 We also provide a function (copy_global_thread_list) to copy global thread list 56 into a new set. The caller of this function is expected to hold lock on 57 LOCK_thd_remove to avoid any removal from the copied set. This function also 58 acquires lock on LOCK_thread_count before the copy operation to 59 avoid any parallel modification to the set and will release the lock at the 60 end of the function. 61 */ 62 typedef std::set<THD*>::iterator Thread_iterator; 63 Thread_iterator global_thread_list_begin(); 64 Thread_iterator global_thread_list_end(); 65 void copy_global_thread_list(std::set<THD*> *new_copy); 66 void add_global_thread(THD *); 67 void remove_global_thread(THD *); 68 69 /* 70 We maintain a separate counter for the number of threads, 71 which can be accessed without LOCK_thread_count. 72 An un-locked read, means that the result is fuzzy of course. 73 This accessor is used by DBUG printing, by signal handlers, 74 and by the 'mysqladmin status' command. 75 */ 76 uint get_thread_count(); 77 78 #endif // GLOBAL_THREADS_INCLUDED 79