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MDEV-22370 safe_mutex: Trying to lock uninitialized mutex at /data/src/10.4-bug/sql/rpl_parallel.cc, line 470 upon shutdown during FTWRL

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Problem:- When we issue FTWRL with shutdown in parallel, there is race between
FTWRL and shutdown. Shutdown might destroy the mutex (pool->LOCK_rpl_thread_pool)
before FTWRL can lock it. So we can get crash on FTWRL thread

Solution:- mysql_mutex_destroy(pool->LOCK_rpl_thread_pool) should wait for
FTWRL thread to complete its work , and then destroy.
So slave_prepare_for_shutdown will just deactivate the pool, and mutex is destroyed
later in end_slave()
This commit is contained in:
Sachin Kumar
2021-04-14 11:23:38 +01:00
parent 3616640a31
commit 355dc74b76
5 changed files with 39 additions and 1 deletions
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4
mysql-test/r/mdev_22370.result Normal file
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@ -0,0 +1,4 @@
connect con1,localhost,root,,;
SET DEBUG_DBUG='+d,mark_busy_mdev_22370';
FLUSH TABLES WITH READ LOCK;
connection default;

17
mysql-test/t/mdev_22370.test Normal file
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@ -0,0 +1,17 @@
#
# MDEV-22370 safe_mutex: Trying to lock uninitialized mutex at
# /data/src/10.4-bug/sql/rpl_parallel.cc, line 470 upon shutdown during FTWRL
#
# Purpose of this test case to test crash while FTWRL and shutdown is in race
# condition
# Shutdown can execute first and destroy the mutex making mutex_lock in pool_mark_busy
# to crash
--source include/have_debug.inc
--connect (con1,localhost,root,,)
SET DEBUG_DBUG='+d,mark_busy_mdev_22370';
--send
FLUSH TABLES WITH READ LOCK;
--connection default
--source include/restart_mysqld.inc

15
sql/rpl_parallel.cc
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@ -455,6 +455,7 @@ pool_mark_busy(rpl_parallel_thread_pool *pool, THD *thd)
So we protect the infrequent operations of FLUSH TABLES WITH READ LOCK and So we protect the infrequent operations of FLUSH TABLES WITH READ LOCK and
pool size changes with this condition wait. pool size changes with this condition wait.
*/ */
DBUG_EXECUTE_IF("mark_busy_mdev_22370",my_sleep(1000000););
mysql_mutex_lock(&pool->LOCK_rpl_thread_pool); mysql_mutex_lock(&pool->LOCK_rpl_thread_pool);
if (thd) if (thd)
{ {
@ -2001,10 +2002,24 @@ rpl_parallel_thread_pool::init(uint32 size)
void void
rpl_parallel_thread_pool::destroy() rpl_parallel_thread_pool::destroy()
{
deactivate();
destroy_cond_mutex();
}
void
rpl_parallel_thread_pool::deactivate()
{ {
if (!inited) if (!inited)
return; return;
rpl_parallel_change_thread_count(this, 0, 1); rpl_parallel_change_thread_count(this, 0, 1);
}
void
rpl_parallel_thread_pool::destroy_cond_mutex()
{
if (!inited)
return;
mysql_mutex_destroy(&LOCK_rpl_thread_pool); mysql_mutex_destroy(&LOCK_rpl_thread_pool);
mysql_cond_destroy(&COND_rpl_thread_pool); mysql_cond_destroy(&COND_rpl_thread_pool);
inited= false; inited= false;

2
sql/rpl_parallel.h
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@ -240,6 +240,8 @@ struct rpl_parallel_thread_pool {
rpl_parallel_thread_pool(); rpl_parallel_thread_pool();
int init(uint32 size); int init(uint32 size);
void destroy(); void destroy();
void deactivate();
void destroy_cond_mutex();
struct rpl_parallel_thread *get_thread(rpl_parallel_thread **owner, struct rpl_parallel_thread *get_thread(rpl_parallel_thread **owner,
rpl_parallel_entry *entry); rpl_parallel_entry *entry);
void release_thread(rpl_parallel_thread *rpt); void release_thread(rpl_parallel_thread *rpt);

2
sql/slave.cc
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@ -977,7 +977,7 @@ void slave_prepare_for_shutdown()
mysql_mutex_unlock(&LOCK_active_mi); mysql_mutex_unlock(&LOCK_active_mi);
// It's safe to destruct worker pool now when // It's safe to destruct worker pool now when
// all driver threads are gone. // all driver threads are gone.
global_rpl_thread_pool.destroy(); global_rpl_thread_pool.deactivate();
} }
/* /*