mariadb/include/mysql/thread_pool_priv.h

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/*
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Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.
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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
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
#ifndef THREAD_POOL_PRIV_INCLUDED
#define THREAD_POOL_PRIV_INCLUDED
/*
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The thread pool requires access to some MySQL server error codes, this is
accessed from mysqld_error.h.
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We need access to the struct that defines the thread pool plugin interface
which is accessed through scheduler.h.
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All accesses to THD variables and functions are defined in this header file.
A thread pool can also use DEBUG_SYNC and must thus include
debug_sync.h
To handle definitions of Information Schema plugins it is also required
to include sql_profile.h and table.h.
*/
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#include <mysqld_error.h> /* To get ER_ERROR_ON_READ */
#define MYSQL_SERVER 1
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#include <scheduler.h>
#include <debug_sync.h>
#include <sql_profile.h>
#include <table.h>
#include <sql_list.h>
/* Needed to get access to scheduler variables */
void* thd_get_scheduler_data(THD *thd);
void thd_set_scheduler_data(THD *thd, void *data);
PSI_thread* thd_get_psi(THD *thd);
void thd_set_psi(THD *thd, PSI_thread *psi);
/* Interface to THD variables and functions */
void thd_set_killed(THD *thd);
void thd_clear_errors(THD *thd);
void thd_set_thread_stack(THD *thd, char *stack_start);
void thd_lock_thread_count(THD *thd);
void thd_unlock_thread_count(THD *thd);
void thd_close_connection(THD *thd);
THD *thd_get_current_thd();
void thd_new_connection_setup(THD *thd, char *stack_start);
void thd_lock_data(THD *thd);
void thd_unlock_data(THD *thd);
bool thd_is_transaction_active(THD *thd);
int thd_connection_has_data(THD *thd);
void thd_set_net_read_write(THD *thd, uint val);
uint thd_get_net_read_write(THD *thd);
void thd_set_mysys_var(THD *thd, st_my_thread_var *mysys_var);
ulong thd_get_net_wait_timeout(THD *thd);
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my_socket thd_get_fd(THD *thd);
BUG#14458232 - CRASH IN THD_IS_TRANSACTION_ACTIVE DURING THREAD POOLING STRESS TEST PROBLEM: Connection stress tests which consists of concurrent kill connections interleaved with mysql ping queries cause the mysqld server which uses thread pool scheduler to crash. FIX: Killing a connection involves shutdown and close of client socket and this can cause EPOLLHUP(or EPOLLERR) events to be to be queued and handled after disarming and cleanup of of the connection object (THD) is being done.We disarm the the connection by modifying the epoll mask to zero which ensure no events come and release the ownership of waiting thread that collect events and then do the cleanup of THD. object.As per the linux kernel epoll source code ( http://lxr.linux.no/linux+*/fs/eventpoll.c#L1771), EPOLLHUP (or EPOLLERR) can't be masked even if we set EPOLL mask to zero. So we disarm the connection and thus prevent execution of any query processing handler/queueing to client ctx. queue by removing the client fd from the epoll set via EPOLL_CTL_DEL. Also there is a race condition which involve the following threads: 1) Thread X executing KILL CONNECTION Y and is in THD::awake and using mysys_var (holding LOCK_thd_data). 2) Thread Y in tp_process_event executing and is being killed. 3) Thread Z receives KILL flag internally and possible call the tp_thd_cleanup function which set thread session variable and changing mysys_var. The fix for the above race is to set thread session variable under LOCK_thd_data. We also do not call THD::awake if we found the thread in the thread list that is to be killed but it's KILL_CONNECTION flag set thus avoiding any possible concurrent cleanup. This patch is approved by Mikael Ronstrom via email review.
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int thd_store_globals(THD* thd);
THD *first_global_thread();
THD *next_global_thread(THD *thd);
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/* Print to the MySQL error log */
void sql_print_error(const char *format, ...);
/* Store a table record */
bool schema_table_store_record(THD *thd, TABLE *table);
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/*
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The thread pool must be able to execute statements using the connection
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state in THD object. This is the main objective of the thread pool to
schedule the start of these commands.
*/
bool do_command(THD *thd);
/*
The thread pool requires an interface to the connection logic in the
MySQL Server since the thread pool will maintain the event logic on
the TCP connection of the MySQL Server. Thus new connections, dropped
connections will be discovered by the thread pool and it needs to
ensure that the proper MySQL Server logic attached to these events is
executed.
*/
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/* Initialise a new connection handler thread */
bool init_new_connection_handler_thread();
/* Set up connection thread before use as execution thread */
bool setup_connection_thread_globals(THD *thd);
/* Prepare connection as part of connection set-up */
bool thd_prepare_connection(THD *thd);
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/* Release auditing before executing statement */
void mysql_audit_release(THD *thd);
/* Check if connection is still alive */
bool thd_is_connection_alive(THD *thd);
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/* Close connection with possible error code */
void close_connection(THD *thd, uint errcode);
/* End the connection before closing it */
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void end_connection(THD *thd);
/* Cleanup the THD object */
void thd_cleanup(THD *thd);
/* Decrement connection counter */
void dec_connection_count();
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/* Destroy THD object */
void delete_thd(THD *thd);
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/*
thread_created is maintained by thread pool when activated since
user threads are created by the thread pool (and also special
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threads to maintain the thread pool). This is done through
inc_thread_created.
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max_connections is needed to calculate the maximum number of threads
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that is allowed to be started by the thread pool. The method
get_max_connections() gets reference to this variable.
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connection_attrib is the thread attributes for connection threads,
the method get_connection_attrib provides a reference to these
attributes.
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*/
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void inc_thread_created(void);
ulong get_max_connections(void);
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pthread_attr_t *get_connection_attrib(void);
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#endif